Category Archives: Moon Colonization

Smaller, outer moon of Mars

Deimos (systematic designation: Mars II)[10] is the smaller and outermost of the two natural satellites of Mars, the other being Phobos. Of similar composition to C and D-type asteroids, Deimos has a mean radius of 6.2km (3.9mi) and takes 30.3hours to orbit Mars.[5] Deimos is 23,460km (14,580mi) from Mars, much farther than Mars's other moon, Phobos.[11] It is named after Deimos, the Ancient Greek god and personification of dread and terror.

Deimos was discovered by Asaph Hall III at the United States Naval Observatory in Washington, D.C. on 12 August 1877, at about 07:48 UTC.[a] Hall, who also discovered Phobos shortly afterwards, had been specifically searching for Martian moons at the time.

The moon is named after Deimos, a figure representing dread in Greek mythology.[10] The name was suggested by academic Henry Madan, who drew from Book XV of the Iliad, where Ares (the Roman god Mars) summons Dread (Deimos) and Fear (Phobos).[17]

The origin of Mars's moons is unknown and the hypotheses are controversial.[18] The main hypotheses are that they formed either by capture or by accretion. Because of the similarity to the composition of C- or D-type asteroids, one hypothesis is that the moons may be objects captured into Martian orbit from the asteroid belt, with orbits that have been circularized either by atmospheric drag or tidal forces,[19] as capture requires dissipation of energy. The current Martian atmosphere is too thin to capture a Phobos-sized object by atmospheric braking.[18] Geoffrey Landis has pointed out that the capture could have occurred if the original body was a binary asteroid that separated due to tidal forces.[20] The main alternative hypothesis is that the moons accreted in the present position. Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a planetesimal.[21][22]

Most recently, Amirhossein Bagheri (ETH Zurich), Amir Khan (ETH Zurich), Michael Efroimsky (US Naval Observatory) and their colleagues proposed a new hypothesis on the origin of the moons. By analyzing the seismic and orbital data from Mars InSight Mission and other missions, they proposed that the moons are born from disruption of a common parent body around 1 to 2.7 billion years ago. The common progenitor of Phobos and Deimos was most probably hit by another object and shattered to form Phobos and Deimos.[23]

Deimos, like Mars' other moon, Phobos, has spectra, albedos, and densities similar to those of a C- or D-type asteroid.[citation needed] Like most bodies of its size, Deimos is highly non-spherical with triaxial dimensions of 15 12.2 11km,[7] making it 56% of the size of Phobos. Deimos is composed of rock rich in carbonaceous material, much like C-type asteroids and carbonaceous chondrite meteorites.[24] It is cratered, but the surface is noticeably smoother than that of Phobos, caused by the partial filling of craters with regolith.[citation needed] The regolith is highly porous and has a radar-estimated density of only 1.471g/cm3.[25]

Escape velocity from Deimos is 5.6m/s.[6] This velocity could theoretically be achieved by a human performing a vertical jump.[26][27] The apparent magnitude of Deimos is 12.45.[8]

Only two geological features on Deimos have been given names. The craters Swift and Voltaire are named after writers who speculated on the existence of two Martian moons before Phobos and Deimos were discovered.[28]

Deimos's orbit is nearly circular and is close to Mars's equatorial plane. Deimos is possibly an asteroid that was perturbed by Jupiter into an orbit that allowed it to be captured by Mars, though this hypothesis is still controversial and disputed.[18] Both Deimos and Phobos have very circular orbits which lie almost exactly in Mars' equatorial plane, and hence a capture origin requires a mechanism for circularizing the initially highly eccentric orbit, and adjusting its inclination into the equatorial plane, most likely by a combination of atmospheric drag and tidal forces;[19] it is not clear that sufficient time was available for this to have occurred for Deimos.[18]

As seen from Mars, Deimos would have an angular diameter of no more than 2.5 minutes (sixty minutes make one degree), one twelfth of the width of the Moon as seen from Earth, and would therefore appear almost star-like to the naked eye.[30] At its brightest ("full moon") it would be about as bright as Venus is from Earth; at the first- or third-quarter phase it would be about as bright as Vega. With a small telescope, a Martian observer could see Deimos's phases, which take 1.2648[31] days (Deimos's synodic period) to run their course.[30]

Unlike Phobos, which orbits so fast that it rises in the west and sets in the east, Deimos rises in the east and sets in the west. The Sun-synodic orbital period of Deimos of about 30.4 hours exceeds the Martian solar day ("sol") of about 24.7 hours by such a small amount that 2.48 days (2.41 sols) elapse between its rising and setting for an equatorial observer. From Deimos-rise to Deimos-rise (or setting to setting), 5.466 days (5.320 sols) elapse.[citation needed]

Because Deimos's orbit is relatively close to Mars and has only a very small inclination to Mars's equator, it cannot be seen from Martian latitudes greater than 82.7.[citation needed]

Deimos's orbit is slowly getting larger, because it is far enough away from Mars and because of tidal acceleration. It is expected to eventually escape Mars's gravity.[32]

Deimos regularly passes in front of the Sun as seen from Mars. It is too small to cause a total eclipse, appearing only as a small black dot moving across the Sun. Its angular diameter is only about 2.5 times the angular diameter of Venus during a transit of Venus from Earth. On 4 March 2004 a transit of Deimos was photographed by Mars rover Opportunity, and on 13 March 2004 a transit was photographed by Mars rover Spirit.[citation needed]

Overall, its exploration history is similar to those of Mars and of Phobos.[33] Deimos has been photographed in close-up by several spacecraft whose primary mission has been to photograph Mars. No landings on Deimos have been made.

The Soviet Phobos program sent two probes to Phobos. In case Phobos 1 succeeded, Phobos 2 could have been sent to Deimos. Both probes launched successfully in July 1988. The first was lost en route to Mars, whereas the second returned some data and images but failed shortly before beginning its detailed examination of Phobos's surface, including a lander.[citation needed]

In 1997 and 1998, the proposed Aladdin mission was selected as a finalist in the NASA Discovery Program. The plan was to visit both Phobos and Deimos, and launch projectiles at the satellites. The probe would collect the ejecta as it performed a slow flyby (~1km/s).[34] These samples would be returned to Earth for study three years later.[35][36] The principal investigator was Carle M. Pieters of Brown University. The total mission cost, including launch vehicle and operations was $247.7 million.[37] Ultimately, the mission chosen to fly was MESSENGER, a probe to the planet Mercury.[38]

In 2008, NASA Glenn Research Center began studying a Phobos and Deimos sample-return mission that would use solar electric propulsion. The study gave rise to the "Hall" mission concept, a New Frontiers-class mission currently under further study.[39]

Also, the sample-return mission called Gulliver has been conceptualized and dedicated to Deimos,[40] in which 1 kilogram (2.2 pounds) of material from Deimos would be returned to Earth.[40]

Another concept of sample-return mission from Phobos and Deimos is OSIRIS-REx2, which would use heritage from the first OSIRIS-REx.[41]

In March 2014, a Discovery class mission was proposed to place an orbiter on Mars orbit by 2021 and study Phobos and Deimos. It is called Phobos And Deimos & Mars Environment (PADME).[42][43]

Human exploration of Deimos could serve as a catalyst for the human exploration of Mars. Recently, it was proposed that the sands of Deimos or Phobos could serve as a valuable material for aerobraking in the colonization of Mars.[44] See Phobos for more detail.

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Deimos (moon) - Wikipedia

Amid the pantheon of Greek gods, few are more revered than Artemis, Goddess of the hunt, chastity, and the moon; Mistress of Animals, Daughter of Zeus and twin sister to Apollo. Famed for her pledge to never marry, feared from that time she turned the peeping Acteon into a stag and set his own hunting dogs upon him, Artemis has stood as a feminist icon for millenia. It seems only fitting then that NASA names after her a trailblazing mission that will see both the first woman and first person of color set foot on the moon, ahead of humanitys first off-planet colony.

In fact, NASA has been naming its missions after Zeus progeny since the advent of spaceflight. There was the Mercury Program (the Roman spelling of Hermes) in 1958, then Gemini in 68 followed by Apollo in 73. NASA took a quick break on the naming convention during the Shuttle era but revived it when it formally established the Artemis program in 2017. Working with the European Space Agency (ESA), Japan Aerospace Exploration Agency (JAXA), Canadian Space Agency (CSA), and a slew of private corporations, NASAs goal for Artemis is simple: to re-establish a human foothold on the moon for the first time since 1972, and stay there.

NASA is building a coalition of partnerships with industry, nations and academia that will help us get to the moon quickly and sustainably, together, then-NASA director Jim Bridenstine said in 2020. Our work to catalyze the US space economy with public-private partnerships has made it possible to accomplish more than ever before. The budget we need to achieve everything laid out in this plan represents bipartisan support from the Congress.

Under the Artemis program, humanity will explore regions of the moon never visited before, uniting people around the unknown, the never seen, and the once impossible, he continued. We will return to the moon robotically beginning next year, send astronauts to the surface within four years, and build a long-term presence on the Moon by the end of the decade.

Story continues

CAPE CANAVERAL, FLORIDA - NOVEMBER 16: NASAs Artemis I Space Launch System (SLS) rocket, with the Orion capsule attached, launches at NASA's Kennedy Space Center on November 16, 2022 in Cape Canaveral, Florida. The Artemis I mission will send the uncrewed spacecraft around the moon to test the vehicle's propulsion, navigation and power systems as a precursor to later crewed mission to the lunar surface. (Photo by Red Huber/Getty Images)

Just as Artemis the Goddess grew out of earlier pre-Hellenistic mythology, Artemis the Program was born from the ashes of the earlier Constellation program from the early 2000s which sought to land on the moon by 2020 specifically the Ares I, Ares V, and Orion Crew Exploration Vehicle that were developed as part of that effort. In 2010, then-President Barack Obama announced that the non-Orion bits of Constellation were being axed and simultaneously called for $6 billion in additional funding as well as the development of a new heavy lift rocket program with a goal of putting humans on Mars by the mid-2030s. This became the NASA Authorization Act of 2010 and formally kicked off development of the Space Launch System, the most powerful rocket NASA has built to date.

The Artemis program was helped further in December of 2017 when former President Donald Trump signed Space Policy Directive 1 (SPD 1). That policy change, provides for a US-led, integrated program with private sector partners for a human return to the moon, followed by missions to Mars and beyond and authorized the campaign that would become Artemis two years later. In 2019, then-Vice President Mike Pence announced that the programs goals were accelerating, the moon landing goal pushed up four years to 2024 though its original goal of Mars in the 2030s remained unchanged.

The directive I am signing today will refocus Americas space program on human exploration and discovery, Trump said at the time. It marks a first step in returning American astronauts to the moon for the first time since 1972, for long-term exploration and use. This time, we will not only plant our flag and leave our footprints we will establish a foundation for an eventual mission to Mars, and perhaps someday, to many worlds beyond.

a diagram of how the Artemis missions will approach the moon

Now, we know NASA can put people on the moon its the keeping them there, alive, thats the issue. The moon, for all its tide-inducing benefits here on Earth, is generally inhospitable to life, what with its general lack of breathable atmosphere and liquid water, weak gravity, massive temperature swings and razor-sharp, statically-charged dust. The first colonists will need power, heat, atmosphere, potable water all of which will have to either be brought from Earth or extracted locally from the surrounding regolith.

Complicating matters, the Moon, at 230,000 miles away, is about a thousand times farther than the International Space Station, and getting a crew with everything they need to survive for more than a few days is going to require multiple trips not just from Earth orbit to the moon but also from lunar orbit down to the surface and back. But high-risk, high-reward logistical nightmares are kind of NASAs whole deal.

As such, the Artemis program is split between the SLS missions, which will eventually bring the human crew to the moon, and the support missions, which will bring everything else. That includes robotic rovers, the Human Landing System, as well as moonbase and Gateway components along with all of the logistical support and infrastructure that they will require.

The SLS missions are built around NASAs new Deep Space Exploration System, which comprises the SLS super heavy-lift launch vehicle, the Orion Spacecraft and the Exploration Ground Systems at Kennedy Space Center (KSC).

Artemis 1 moon sequence

The Space Launch System is the single most powerful rocket humanity has built and, given its modular, evolvable design, will likely continue to be for the foreseeable future. Its initial configuration, dubbed Block 1, consists of just the core stage with four RS-25 engines and two, five-segment solid rocket boosters. Once the SLS breaks atmosphere, its Interim Cryogenic Propulsion Stage takes over for in-space propulsion.

Those RS-25s are the same engines that flew on the Space Shuttle. Aerojet Rocketdyne of Sacramento, California is updating and upgrading 16 of them for use in the modern era bringing them up to standard for use with the SLS with a new engine controller, new nozzle insulation, and 512,000 pounds of thrust. Altogether, the core stage will produce 8.8 million pounds of thrust and be capable of pushing 27 metric tons (22,000 sqft) of cargo out to the moon at speeds in excess of 24,500 miles per hour. The Artemis 1 mission that launched in November, as well as the next two Artemis missions, are slash will be powered by Block 1 rockets.

SLS Block builds

Block 1B rockets will include an Exploration Upper Stage (EUS) built by Boeing and composed of four RL10C-3 engines that produce almost four times more thrust than the one RL10B-2 engine that powers the ICPS, per NASA. That additional engine will enable the space agency to haul 38 tons of cargo out of Earths gravity well. This updated block will provide NASA a bit more flexibility in its launches. A 1B rocket can be configured to lift the Orion spacecraft or cargo loads into deep space as easily as it can be for hauling large cargoes to the moon or Mars. NASA plans to lift unwieldy portions of the moonbase and Gateway into space with it.

The SLS final form (for now) will be Block 2. Standing more than 30 stories tall, weighing the equivalent of 10 fully-loaded 747s, the block 2 blasting 9.2 million pounds of thrust (20 percent more than the Saturn V) to push 46 metric tons of stuff (taking up as much as 54,000 square feet) into deep space. Once that configuration comes online, NASA expects it to take on much of the heavy lifting (sorry not sorry) in delivering crews and cargo to the moon.

Riding atop the SLSs multi-ton controlled explosions is the Orion Spacecraft, the first crew capsule designed for deep space exploration in more than a generation. Designed and built with help from the ESA, the Orion sandwiches a four-person crew cabin in between a services module that holds all of the important life support, navigation and propulsion systems, and a Launch Abort System (LAS) that will forcibly eject the crew capsule from the larger launch vehicle if a catastrophic failure occurs during takeoff.

The 50-foot tall LAS weighs 16,000 pounds and is designed to engage within milliseconds of a launch going sideways, lifting the crew cabin away from the rest of the SLS at Mach 1.2 using the 400,000 pounds of thrust produced by the abort motor. Its attitude control motor provides another 7,000 pounds of thrust to keep the capsule upright during escape while the jettison motor will separate the LAS from the cabin once clear, the latter deploying a parachute ahead of its upcoming water landing.

The LAS actually predates Orion by four years. The LAS was first integrated into a Delta IV and flown at the White Sands test facility in New Mexico in 2010 while the (uncrewed) Orion Exploration Flight Test-1 didnt take off for its four-hour, two orbit jaunt until 2014.

The Orion main cabin is just under 16 feet tall and just over 16 feet in diameter. Its four wing solar array produces 11kW of power and the attached service module holds enough air and water to keep the crew alive, if a bit panicked and sir-crazy, for up to three weeks.

CAPE CANAVERAL, FL - NOVEMBER 3: In this handout photo provided by NASA, NASAs Space Launch System (SLS) rocket with the Orion spacecraft aboard is seen atop the mobile launcher as Crawler Transporter-2 (CT-2) begins to climb the ramp at Launch Pad 39B at NASAs Kennedy Space Center on November 3, 2022 in Cape Canaveral, Florida. NASA's Artemis I mission is the first integrated test of the agency's deep space exploration systems: the Orion spacecraft, SLS rocket, and supporting ground systems. Launch of the uncrewed flight test is targeted for November 14 at 12:07 a.m. EST. (Photo by Joel Kowsky/NASA via Getty Images)

Located at the Kennedy Space Center in Florida, the Artemis programs Exploration Ground Systems (EGS) is tasked with developing and enacting the facilities and operations necessary to conduct SLS missions. That includes the Vehicle Assembly Building, the Launch Control Center, the Firing Rooms, Mobile Launchers 1 and 2, the Crawlers that haul rockets out to the launchpads, and also the launchpads specifically Launch Pad 39B. Teams have been working to modernize many of those facilities and NASA notes that it, has successfully upgraded its processes, facilities, and ground support equipment to safely handle rockets and spacecraft during assembly, transport, and launch.

NASA already has five main Artemis launches scheduled. The uncrewed Artemis I, again, successfully launched in November. Artemis II, which will carry four live astronauts for the first time but only loop around the moon, launches in 2024. Artemis III will go up in 2025 and is expected to be the first to actually set down on the moon. Artemis IV is slated for 2027 and will deliver half of the lunar Gateway (as well as debut the EUS) while Artemis V is set to deliver the other half of the Gateway in 2028. From there, NASA has some thoughts on Artemis missions VI (2029) through X (2033) but has not finalized any details as of yet.

We need several years in orbit and on the surface of the moon to build operational confidence for conducting long-term work and supporting life away from Earth before we can embark on the first multi-year human mission to Mars, Bridenstine said in 2020. The sooner we get to the moon, the sooner we get American astronauts to Mars.

the capstone cubesat flying over the moon with the sun in the distance

But before we can build confidence in our ability to survive on Mars, we need to build confidence in our ability to survive on the moon. The Artemis support missions will do just that. The Capstone Mission ("Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment"), for example, successfully launched a 55-pound cubesat in June to confirm NASAs math for the much larger Gateways future orbital path. While in orbit, the Capstone will communicate and coordinate some of its maneuvers with the Lunar Reconnaissance Orbiter which has been circling the moon since 2009.

In 2023, NASA also plans to launch the VIPER robotic rover to the moons South Pole where it will search the lowest, darkest, coldest craters for accessible water ice. Finding a source for H2O is of paramount importance to the long-term viability of the colony. In space, water isnt just for drinking and bathing it can be split into its component atoms and used to fuel our oxidizing rockets, potentially turning the Moon into an orbital gas station as we push farther out from Earth. The rover, and others like it, will be delivered to the surface as part of NASAs Commercial Lunar Payload Services (CLPS) program.

It wasnt until the mid 1990s that NASA even confirmed the presence of water ice on the moon and only two years ago did they discovered ice accessible from the moons surface. We had indications that H2O the familiar water we know might be present on the sunlit side of the moon, Paul Hertz, director of the Astrophysics Division in the Science Mission Directorate at NASA Headquarters, said at the time. Now we know it is there. This discovery challenges our understanding of the lunar surface and raises intriguing questions about resources relevant for deep space exploration.

Similarly, any habitat established on the surface will need an ample supply of electricity to remain online. Solar charging is one obvious choice (that lack of atmosphere is finally coming in handy) but NASA has never been one to underprepare and has already selected three aerospace companies to develop nuclear power sources for potential deployment.

Gateway components blowup

In addition to a surface installation, NASA plans on putting a full-fledged space station, dubbed the Lunar Gateway, into orbit around the moon where it will serve much the same purpose as the ISS does today. Visiting researchers will stay aboard the pressurized Habitation and Logistics Outpost (HALO) module where theyll have access to research facilities, remote rover controls and docking for both Orion capsules from Earth and HLS (Human Landing System) landers to the moons surface. A 60kW solar plant will provide power to the station, which also serves as a communications relay hub with the planet. The stations position around the moon will also provide a unique astronomical perspective for future research.

The Gateway will very much be an international operation. As NASA points out, Canadas CSA is providing advanced robotics for use upon the station, the ESA is supplying a second living module called the International Habitat (IHab) as well as the ESPRIT communications module and an array of research cubesats. Japans JAXA will kick in additional habitat components and assist with resupply logistics.

From the Gateway, astronauts and researchers will ferry down to the moons surface to collect samples, run experiments and conduct observations aboard the Human Landing System, a reusable lunar lander program currently being operated out of Marshall Space Flight Center in Huntsville, Alabama.

NASA selected SpaceXs Starship for its initial landing system in April 2021, awarding the company $2.9 billion to further the vehicles development. The agency then awarded SpaceX with another $1.15 billion this past November as part of the Option B contract modification. The extra money will help fund planned upgrades to the spacecraft, which is being modified from the base Starship design for use on and around the moons surface.

Continuing our collaborative efforts with SpaceX through Option B furthers our resilient plans for regular crewed transportation to the lunar surface and establishing a long-term human presence under Artemis, Lisa Watson-Morgan, NASA HLS program manager, said in November. This critical work will help us focus on the development of sustainable, service-based lunar landers anchored to NASAs requirements for regularly recurring missions to the lunar surface.

Researchers, however, will not be content to travel nearly a quarter million miles just to set down on the moon and look out the landers windows. Instead, theyll be free to wander around the surface safely ensconced in spacewalk equipment supplied by Axiom Space and Collins Aerospace.

With these awards, NASA and our partners will develop advanced, reliable spacesuits that allow humans to explore the cosmos unlike ever before, said Vanessa Wyche, director of NASAs Johnson Space Center in Houston, said in June. By partnering with industry, we are efficiently advancing the necessary technology to keep Americans on a path of successful discovery on the International Space Station and as we set our sights on exploring the lunar surface.

Those researchers wont be on foot either. Just as the Apollo astronauts famously bounced around on NASAs first-gen lunar rovers, the Artemis missions will use new Lunar Terrain Vehicles. The unpressurized buggies are currently still in development but NASA expects to have a finalized proposal ready by next year and have the LTVs ready for surface service by 2028.

When not in use, the LTVs will be parked at NASAs Artemis Base Camp at the lunar South Pole, alongside a pressurized version designed for longer-duration expeditions. The surface habitat itself will be able to support up to four residents at a time and provide communications, equipment storage, power and, most importantly, robust radiation shielding (and theres the downside of not having an atmosphere). A site hasnt yet been officially selected, though mission planners are looking for areas near the regions permanently shadowed craters where water ice is expected to be most easily accessible (aside from the negative 280 degree temperatures and perpetual darkness).

On each new trip, astronauts are going to have an increasing level of comfort with the capabilities to explore and study more of the moon than ever before, Kathy Lueders, associate administrator for human spaceflight at NASA Headquarters, said in 2020. With more demand for access to the moon, we are developing the technologies to achieve an unprecedented human and robotic presence 240,000 miles from home. Our experience on the moon this decade will prepare us for an even greater adventure in the universe human exploration of Mars.

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Everything NASA is taking to the moon before colonizing Mars

Chinese lunar research program (2004 present)

The Chinese Lunar Exploration Program (CLEP; Chinese: ; pinyin: Zhnggu Tnyu), also known as the Chang'e Project (Chinese: ; pinyin: Chng' Gngchng) after the Chinese moon goddess Chang'e, is an ongoing series of robotic Moon missions by the China National Space Administration (CNSA). The program incorporates lunar orbiters, landers, rovers and sample return spacecraft, launched using Long March rockets. Launches and flights are monitored by a telemetry, tracking, and command (TT&C) system, which uses 50-meter (160-foot) radio antennas in Beijing and 40-meter (130-foot) antennas in Kunming, Shanghai, and rmqi to form a 3,000-kilometer (1,900-mile) VLBI antenna.[1][2] A proprietary ground application system is responsible for downlink data reception.

Ouyang Ziyuan, a geologist, chemical cosmologist, and the program's chief scientist, was among the first to advocate the exploitation not only of known lunar reserves of metals such as titanium, but also of helium-3, an ideal fuel for future nuclear fusion power plants. Ye Peijian serves as the program's chief commander and chief designer.[3] Scientist Sun Jiadong is the program's general designer and Sun Zezhou is deputy general designer. The leading program manager is Luan Enjie.

The first spacecraft of the program, the Chang'e 1 lunar orbiter, was launched from Xichang Satellite Launch Center on 24 October 2007,[4] having been delayed from the initial planned date of 1719 April 2007.[5] A second orbiter, Chang'e 2, was launched on 1 October 2010.[6][7] Chang'e 3, which includes a lander and rover, was launched on 1 December 2013 and successfully soft-landed on the Moon on 14 December 2013. Chang'e 4, which includes a lander and rover, was launched on 7 December 2018 and landed on 3 January 2019 on the South Pole-Aitken Basin, on the far side of the Moon. A sample return mission, Chang'e 5, which launched on 23 November 2020 and returned on 16 December in the same year, brought 1,731 g (61.1oz) of lunar samples back to earth.[8]

As indicated by the official insignia, the shape of a calligraphic nascent lunar crescent with two human footprints at its center reminiscent of the Chinese character , the Chinese character for "Moon", the ultimate objective of the program is to pave the way for a crewed mission to the Moon. China National Space Administration head Zhang Kejian announced that China is planning to build a scientific research station on the Moon's south pole "within the next 10 years," (20192029).[9]

The Chinese Lunar Exploration Program is divided into four main operational phases, with each mission serving as a technology demonstrator in preparation for future missions. International cooperation in the form of various payloads and a robotic station is invited by China.[10]

The first phase entailed the launch of two lunar orbiters, and is now effectively complete.

Before Chang-e 5, no lunar sample-return was conducted in over four decades.

The second phase is ongoing, and incorporates spacecraft capable of soft-landing on the Moon and deploying lunar rovers.

The third phase included a lunar sample-return mission.

After the "3 steps" phase is done, the phase for the development of an autonomous lunar research station near the Moon's south pole will commence.[10][14][15]

As of 2019[update], China was reviewing preliminary studies for a crewed lunar landing mission in the 2030s,[23][24] and possibly building an outpost near the lunar south pole with international cooperation.[10][23]

In 2021, China and Russia announced they will be building a moon base together, also formally invited more countries and international organizations to join their International Lunar Research Station (ILRS) project being developed by the two nations,[25] as a competitor to the American Artemis Program.[26]

Planned hard landing Planned soft landing

The biggest challenge in Phase I of the program was the operation of the TT&C system, because its transmission capability needed sufficient range to communicate with the probes in lunar orbit.[28] China's standard satellite telemetry had a range of 80,000 kilometers (50,000 miles), but the distance between the Moon and the Earth can exceed 400,000 kilometers (250,000 miles) when the Moon is at apogee. In addition, the Chang'e probes had to carry out many attitude maneuvers during their flights to the Moon and during operations in lunar orbit. The distance across China from east to west is 5,000 kilometers (3,100 miles),[29] forming another challenge to TT&C continuity. At present, the combination of the TT&C system and the Chinese astronomical observation network has met the needs of the Chang'e program,[30] but only by a small margin.

The complexity of the space environment encountered during the Chang'e missions imposed strict requirements for environmental adaptability and reliability of the probes and their instruments. The high-radiation environment in Earth-Moon space required hardened electronics to prevent electromagnetic damage to spacecraft instruments. The extreme temperature range, from 130 degrees Celsius (266 degrees Fahrenheit) on the side of the spacecraft facing the Sun to 170 degrees Celsius (274 degrees Fahrenheit) on the side facing away from the Sun, imposed strict requirements for temperature control in the design of the detectors.

Given the conditions of the three-body system of the Earth, Moon and a space probe, the orbit design of lunar orbiters is more complicated than that of Earth-orbiting satellites, which only deal with a two-body system. The Chang'e 1 and Chang'e 2 probes were first sent into highly elliptical Earth orbits. After separating from their launch vehicles, they entered an Earth-Moon transfer orbit through three accelerations in the phase-modulated orbit. These accelerations were conducted 16, 24, and 48 hours into the missions, during which several orbit adjustments and attitude maneuvers were carried out so as to ensure the probes' capture by lunar gravity. After operating in the Earth-Moon orbit for 45 days, each probe entered a lunar acquisition orbit. After entering their target orbits, conducting three braking maneuvers and experiencing three different orbit phases, Chang'e 1 and Chang'e 2 carried out their missions.

Lunar orbiters have to remain properly oriented with respect to the Earth, Moon and Sun. All onboard detectors must be kept facing the lunar surface in order to complete their scientific missions, communication antennas have to face the Earth in order to receive commands and transfer scientific data, and solar panels must be oriented toward the Sun in order to acquire power. During lunar orbit, the Earth, the Moon and the Sun also move, so attitude control is a complex three-vector control process. The Chang'e satellites need to adjust their attitude very carefully to maintain an optimal angle towards all three bodies.

During the second phase of the program, in which the spacecraft were required to soft-land on the lunar surface, it was necessary to devise a system of automatic hazard avoidance in order that the landers would not attempt to touch down on unsuitable terrain. Chang'e 3 utilized a computer vision system in which the data from a down-facing camera, as well as 2 ranging devices, were processed using specialized software. The software controlled the final stages of descent, adjusting the attitude of the spacecraft and the throttle of its main engine. The spacecraft hovered first at 100 meters (330 feet), then at 30 meters (98 feet), as it searched for a suitable spot to set down. The Yutu rover is also equipped with front-facing stereo cameras and hazard avoidance technology.

In November 2017, China and Russia signed an agreement on cooperative lunar and deep space exploration.[31] The agreement includes six sectors, covering lunar and deep space, joint spacecraft development, space electronics, Earth remote sensing data, and space debris monitoring.[31][32][33] Russia may also look to develop closer ties with China in human spaceflight,[31] and even shift its human spaceflight cooperation from the US to China and build a crewed lunar lander.[34]

Chang'e 4 lander on the Moon

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Chinese Lunar Exploration Program - Wikipedia

Natural satellite orbiting the Earth

The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet,[f] with a diameter about one-quarter that of Earth (comparable to the width of Australia).[16] The Moon is a planetary-mass object with a differentiated rocky body, making it a satellite planet under the geophysical definitions of the term and larger than all known dwarf planets of the Solar System.[17] It lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's at 0.1654g, with Jupiter's moon Io being the only satellite in the Solar System known to have a higher surface gravity and density.

Orbiting Earth at an average distance of 384,400km (238,900mi), or about 30 times Earth's diameter, its gravitational influence very slowly lengthens Earth's day and is the main driver of Earth's tides. The Moon's orbit around Earth has a sidereal period of 27.3 days. During each synodic period of 29.5 days, the amount of visible surface illuminated by the Sun varies from none up to 100%, resulting in lunar phases that form the basis for the months of a lunar calendar. The Moon is tidally locked to Earth, which means that the length of a full rotation of the Moon on its own axis causes its same side (the near side) to always face Earth, and the somewhat longer lunar day is the same as the synodic period. However, 59% of the total lunar surface can be seen from Earth through shifts in perspective due to libration.

The most widely accepted origin explanation posits that the Moon formed 4.51billion years ago, not long after Earth, out of the debris from a giant impact between the planet and a hypothesized Mars-sized body called Theia. It then receded to a wider orbit because of tidal interaction with the Earth. The near side of the Moon is marked by dark volcanic maria ("seas"), which fill the spaces between bright ancient crustal highlands and prominent impact craters. Most of the large impact basins and mare surfaces were in place by the end of the Imbrian period, some three billion years ago. The lunar surface is relatively non-reflective, with a reflectance just slightly brighter than that of worn asphalt. However, because it has a large angular diameter, the full moon is the brightest celestial object in the night sky. The Moon's apparent size is nearly the same as that of the Sun, allowing it to cover the Sun almost completely during a total solar eclipse.

Both the Moon's prominence in Earth's sky and its regular cycle of phases have provided cultural references and influences for human societies throughout history. Such influences can be found in language, calendar systems, art, and mythology.The first artificial object to reach the Moon was the Soviet Union's Luna 2 uncrewed spacecraft in 1959; this was followed by the first successful soft landing by Luna 9 in 1966. The only human lunar missions to date have been those of the United States' Apollo program, which landed twelve men on the surface between 1969 and 1972. These and later uncrewed missions returned lunar rocks that have been used to develop a detailed geological understanding of the Moon's origins, internal structure, and subsequent history.

The usual English proper name for Earth's natural satellite is simply Moon, with a capital M.[18][19] The noun moon is derived from Old English mna, which (like all its Germanic cognates) stems from Proto-Germanic *mnn,[20] which in turn comes from Proto-Indo-European *mnsis "month"[21] (from earlier *mnt, genitive *mneses) which may be related to the verb "measure" (of time).[22]

Occasionally, the name Luna is used in scientific writing[23] and especially in science fiction to distinguish the Earth's moon from others, while in poetry "Luna" has been used to denote personification of the Moon.[24] Cynthia is another poetic name, though rare, for the Moon personified as a goddess,[25] while Selene (literally "Moon") is the Greek goddess of the Moon.

The usual English adjective pertaining to the Moon is "lunar", derived from the Latin word for the Moon, lna. The adjective selenian ,[26] derived from the Greek word for the Moon, seln, and used to describe the Moon as a world rather than as an object in the sky, is rare,[27] while its cognate selenic was originally a rare synonym[28] but now nearly always refers to the chemical element selenium.[29] The Greek word for the Moon does however provide us with the prefix seleno-, as in selenography, the study of the physical features of the Moon, as well as the element name selenium.[30][31]

The Greek goddess of the wilderness and the hunt, Artemis, equated with the Roman Diana, one of whose symbols was the Moon and who was often regarded as the goddess of the Moon, was also called Cynthia, from her legendary birthplace on Mount Cynthus.[32] These names Luna, Cynthia and Selene are reflected in technical terms for lunar orbits such as apolune, pericynthion and selenocentric.

The astronomical symbol for the Moon is a crescent, , for example in M 'lunar mass' (also ML).

Millions of years before present

Isotope dating of lunar samples suggests the Moon formed around 50million years after the origin of the Solar System.[33][34] Historically, several formation mechanisms have been proposed,[35] but none satisfactorily explains the features of the EarthMoon system. A fission of the Moon from Earth's crust through centrifugal force[36] would require too great an initial rotation rate of Earth.[37] Gravitational capture of a pre-formed Moon[38] depends on an unfeasibly extended atmosphere of Earth to dissipate the energy of the passing Moon.[37] A co-formation of Earth and the Moon together in the primordial accretion disk does not explain the depletion of metals in the Moon.[37] None of these hypotheses can account for the high angular momentum of the EarthMoon system.[39]

The prevailing theory is that the EarthMoon system formed after a giant impact of a Mars-sized body (named Theia) with the proto-Earth. The impact blasted material into orbit about the Earth and the material accreted and formed the Moon[40][41] just beyond the Earth's Roche limit of ~2.56R.[42]

Giant impacts are thought to have been common in the early Solar System. Computer simulations of giant impacts have produced results that are consistent with the mass of the lunar core and the angular momentum of the EarthMoon system. These simulations show that most of the Moon derived from the impactor, rather than the proto-Earth.[43] However, more recent simulations suggest a larger fraction of the Moon derived from the proto-Earth.[44][45][46][47] Other bodies of the inner Solar System such as Mars and Vesta have, according to meteorites from them, very different oxygen and tungsten isotopic compositions compared to Earth. However, Earth and the Moon have nearly identical isotopic compositions. The isotopic equalization of the Earth-Moon system might be explained by the post-impact mixing of the vaporized material that formed the two,[48] although this is debated.[49]

The impact would have released enough energy to liquefy both the ejecta and the Earth's crust, forming a magma ocean. The liquefied ejecta could have then re-accreted into the EarthMoon system.[50][51] Similarly, the newly formed Moon would have had its own lunar magma ocean; its depth is estimated from about 500km (300 miles) to 1,737km (1,079 miles).[50]

While the giant-impact theory explains many lines of evidence, some questions are still unresolved, most of which involve the Moon's composition.[52][example needed]Above a high resolution threshold for simulations, a study published in 2022 finds that giant impacts can immediately place a satellite with similar mass and iron content to the Moon into orbit far outside Earth's Roche limit. Even satellites that initially pass within the Roche limit can reliably and predictably survive, by being partially stripped and then torqued onto wider, stable orbits.[53]

After the Moon's formation the Moon settled in orbit around Earth much closer than today, making both bodies appear much larger in each's sky and causing on both more frequent and stronger eclipses and tidal effects.[54]Since then, due to tidal acceleration, the Moon's orbit around Earth has become significantly larger as well as longer, tidally locking the so-called lunar near side, always facing Earth with this same side.

The post formation cooled lunar surface has been shaped by large and many small impact events, retaining a broadly cratered landscape of all ages, as well as by volcanic activity, producing the prominent lunar maria. Volcanically active until 1.2billion years ago, most of the Moon's mare basalts erupted during the Imbrian period, 3.33.7billion years ago, though some being as young as 1.2billion years[55] and some as old as 4.2billion years.[56] The causes for the eruption of mare basalts, particularly their uneven occurrence on mainly the near-side, like the lunar highlands on the far side, has been an unresolved issue due to differing explanations. One explanation suggests that large meteorites were hitting the Moon in its early history leaving large craters which then were filled with lava. Other explanations suggest processes of lunar volcanism.[57]

The Moon is a very slightly scalene ellipsoid due to tidal stretching, with its long axis displaced 30 from facing the Earth, due to gravitational anomalies from impact basins. Its shape is more elongated than current tidal forces can account for. This 'fossil bulge' indicates that the Moon solidified when it orbited at half its current distance to the Earth, and that it is now too cold for its shape to adjust to its orbit.[58]

The Moon is by size and mass the fifth largest natural satellite of the Solar System, categorizeable as one of its planetary-mass moons, making it a satellite planet under the geophysical definitions of the term.[17] It is smaller than Mercury and considerably larger than the largest dwarf planet of the Solar System, Pluto. While the minor-planet moon Charon of the Pluto-Charon system is larger relative to Pluto,[f][59] the Moon is the largest natural satellite of the Solar System relative to their primary planets.[g]

The Moon's diameter is about 3,500km, more than a quarter of Earth's, with the face of the Moon comparable to the width of Australia.[16] The whole surface area of the Moon is about 38 million square kilometers, slightly less than the area of the Americas (North and South America).

The Moon's mass is 1/81 of Earth's,[60] being the second densest among the planetary moons, and having the second highest surface gravity, after Io, at 0.1654g and an escape velocity of 2.38km/s (8600km/h; 5300mph).

The Moon is a differentiated body that was initially in hydrostatic equilibrium but has since departed from this condition.[61] It has a geochemically distinct crust, mantle, and core. The Moon has a solid iron-rich inner core with a radius possibly as small as 240 kilometres (150mi) and a fluid outer core primarily made of liquid iron with a radius of roughly 300 kilometres (190mi). Around the core is a partially molten boundary layer with a radius of about 500 kilometres (310mi).[62][63] This structure is thought to have developed through the fractional crystallization of a global magma ocean shortly after the Moon's formation 4.5billion years ago.[64]

Crystallization of this magma ocean would have created a mafic mantle from the precipitation and sinking of the minerals olivine, clinopyroxene, and orthopyroxene; after about three-quarters of the magma ocean had crystallised, lower-density plagioclase minerals could form and float into a crust atop.[65] The final liquids to crystallise would have been initially sandwiched between the crust and mantle, with a high abundance of incompatible and heat-producing elements.[1] Consistent with this perspective, geochemical mapping made from orbit suggests a crust of mostly anorthosite.[15] The Moon rock samples of the flood lavas that erupted onto the surface from partial melting in the mantle confirm the mafic mantle composition, which is more iron-rich than that of Earth.[1] The crust is on average about 50 kilometres (31mi) thick.[1]

The Moon is the second-densest satellite in the Solar System, after Io.[66] However, the inner core of the Moon is small, with a radius of about 350 kilometres (220mi) or less,[1] around 20% of the radius of the Moon. Its composition is not well understood, but is probably metallic iron alloyed with a small amount of sulfur and nickel; analyses of the Moon's time-variable rotation suggest that it is at least partly molten.[67] The pressure at the lunar core is estimated to be 5GPa (49,000atm).[68]

The Moon has an external magnetic field of less than 0.2 nanoteslas,[69] or less than one hundred thousandth that of Earth. The Moon does not currently have a global dipolar magnetic field and only has crustal magnetization likely acquired early in its history when a dynamo was still operating.[70][71] However, early in its history, 4 billion years ago, its magnetic field strength was likely close to that of Earth today.[69] This early dynamo field apparently expired by about one billion years ago, after the lunar core had completely crystallized.[69] Theoretically, some of the remnant magnetization may originate from transient magnetic fields generated during large impacts through the expansion of plasma clouds. These clouds are generated during large impacts in an ambient magnetic field. This is supported by the location of the largest crustal magnetizations situated near the antipodes of the giant impact basins.[72]

The Moon's gravitational field is not uniform. The details of the gravitational field have been measured through tracking the Doppler shift of radio signals emitted by orbiting spacecraft. The main lunar gravity features are mascons, large positive gravitational anomalies associated with some of the giant impact basins, partly caused by the dense mare basaltic lava flows that fill those basins.[73][74] The anomalies greatly influence the orbit of spacecraft about the Moon. There are some puzzles: lava flows by themselves cannot explain all of the gravitational signature, and some mascons exist that are not linked to mare volcanism.[75]

On average the Moon's surface gravity is 1.62m/s2[4] (0.1654g; 5.318ft/s2), about half of the surface gravity of Mars and about a sixth of Earth's. The surface of the Moon, having a surface pressure of 1010Pa, lacks any significant atmosphere to moderate the extreme conditions of the surface.

Ionizing radiation from cosmic rays, the Sun and the resulting neutron radiation[76] produce radiation levels on average of 1,369 microsieverts per day, which is about 2-3 times more than on the International Space Station at about 400 km above Earth in orbit,[77] 5-10 times more than during a trans-Atlantic flight,[78] 200 times more than on Earth's surface.[77] For further comparison radiation on a flight to Mars is about 1.84 millisieverts per day and on Mars 0.64 millisieverts per day.[79]

The Moon's axial tilt with respect to the ecliptic is only 1.5427,[8][80] much less than the 23.44 of Earth. Because of this small tilt, the Moon's solar illumination varies much less with season than on Earth and it allows for the existence of some peaks of eternal light at the Moon's north pole, at the rim of the crater Peary.

The surface is exposed to drastic temperature differences ranging from 140C to 171C depending on the solar irradiance.Because of the lack of atmosphere, temperatures of different areas vary particularly upon whether they are in sunlight or shadow,[81] making topographical details play a decisive role on local surface temperatures.[82]Parts of many craters, particularly the bottoms of many polar craters,[83] are permanently shadowed, these "craters of eternal darkness" have extremely low temperatures. The Lunar Reconnaissance Orbiter measured the lowest summer temperatures in craters at the southern pole at 35K (238C; 397F)[84] and just 26K (247C; 413F) close to the winter solstice in the north polar crater Hermite. This is the coldest temperature in the Solar System ever measured by a spacecraft, colder even than the surface of Pluto.[82]

These extreme conditions for example are considered making it unlikely for spacecrafts to harbor bacterial spores at the Moon longer than just one lunar orbit.[85]

The Moon has an atmosphere so tenuous as to be nearly vacuum, with a total mass of less than 10 tonnes (9.8 long tons; 11 short tons).[90] The surface pressure of this small mass is around 3 1015atm (0.3nPa); it varies with the lunar day. Its sources include outgassing and sputtering, a product of the bombardment of lunar soil by solar wind ions.[15][91] Elements that have been detected include sodium and potassium, produced by sputtering (also found in the atmospheres of Mercury and Io); helium-4 and neon[92] from the solar wind; and argon-40, radon-222, and polonium-210, outgassed after their creation by radioactive decay within the crust and mantle.[93][94] The absence of such neutral species (atoms or molecules) as oxygen, nitrogen, carbon, hydrogen and magnesium, which are present in the regolith, is not understood.[93] Water vapor has been detected by Chandrayaan-1 and found to vary with latitude, with a maximum at ~6070degrees; it is possibly generated from the sublimation of water ice in the regolith.[95] These gases either return into the regolith because of the Moon's gravity or are lost to space, either through solar radiation pressure or, if they are ionized, by being swept away by the solar wind's magnetic field.[93]

Studies of Moon magma samples retrieved by the Apollo missions demonstrate that the Moon had once possessed a relatively thick atmosphere for a period of 70 million years between 3 and 4 billion years ago. This atmosphere, sourced from gases ejected from lunar volcanic eruptions, was twice the thickness of that of present-day Mars. The ancient lunar atmosphere was eventually stripped away by solar winds and dissipated into space.[96]

A permanent Moon dust cloud exists around the Moon, generated by small particles from comets. Estimates are 5 tons of comet particles strike the Moon's surface every 24 hours, resulting in the ejection of dust particles. The dust stays above the Moon approximately 10 minutes, taking 5 minutes to rise, and 5 minutes to fall. On average, 120 kilograms of dust are present above the Moon, rising up to 100 kilometers above the surface. Dust counts made by LADEE's Lunar Dust EXperiment (LDEX) found particle counts peaked during the Geminid, Quadrantid, Northern Taurid, and Omicron Centaurid meteor showers, when the Earth, and Moon pass through comet debris. The lunar dust cloud is asymmetric, being more dense near the boundary between the Moon's dayside and nightside.[97][98]

The topography of the Moon has been measured with laser altimetry and stereo image analysis.[99] Its most extensive topographic feature is the giant far-side South PoleAitken basin, some 2,240km (1,390mi) in diameter, the largest crater on the Moon and the second-largest confirmed impact crater in the Solar System.[100][101] At 13km (8.1mi) deep, its floor is the lowest point on the surface of the Moon.[100][102] The highest elevations of the Moon's surface are located directly to the northeast, which might have been thickened by the oblique formation impact of the South PoleAitken basin.[103] Other large impact basins such as Imbrium, Serenitatis, Crisium, Smythii, and Orientale possess regionally low elevations and elevated rims.[100] The far side of the lunar surface is on average about 1.9km (1.2mi) higher than that of the near side.[1]

The discovery of fault scarp cliffs suggest that the Moon has shrunk by about 90 metres (300ft) within the past billion years.[104] Similar shrinkage features exist on Mercury. Mare Frigoris, a basin near the north pole long assumed to be geologically dead, has cracked and shifted. Since the Moon doesn't have tectonic plates, its tectonic activity is slow and cracks develop as it loses heat.[105]

The main features visible from Earth by the naked eye are dark and relatively featureless lunar plains called maria (singular mare; Latin for "seas", as they were once believed to be filled with water)[106] are vast solidified pools of ancient basaltic lava. Although similar to terrestrial basalts, lunar basalts have more iron and no minerals altered by water.[107] The majority of these lava deposits erupted or flowed into the depressions associated with impact basins. Several geologic provinces containing shield volcanoes and volcanic domes are found within the near side "maria".[108]

Almost all maria are on the near side of the Moon, and cover 31% of the surface of the near side[60] compared with 2% of the far side.[109] This is likely due to a concentration of heat-producing elements under the crust on the near side, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt.[65][110][111] Most of the Moon's mare basalts erupted during the Imbrian period, 3.33.7billion years ago, though some being as young as 1.2billion years[55] and as old as 4.2billion years.[56]

In 2006, a study of Ina, a tiny depression in Lacus Felicitatis, found jagged, relatively dust-free features that, because of the lack of erosion by infalling debris, appeared to be only 2 million years old.[112] Moonquakes and releases of gas indicate continued lunar activity.[112] Evidence of recent lunar volcanism has been identified at 70 irregular mare patches, some less than 50 million years old. This raises the possibility of a much warmer lunar mantle than previously believed, at least on the near side where the deep crust is substantially warmer because of the greater concentration of radioactive elements.[113][114][115][116] Evidence has been found for 210 million years old basaltic volcanism within the crater Lowell,[117][118] inside the Orientale basin. Some combination of an initially hotter mantle and local enrichment of heat-producing elements in the mantle could be responsible for prolonged activities on the far side in the Orientale basin.[119][120]

The lighter-colored regions of the Moon are called terrae, or more commonly highlands, because they are higher than most maria. They have been radiometrically dated to having formed 4.4billion years ago, and may represent plagioclase cumulates of the lunar magma ocean.[56][55] In contrast to Earth, no major lunar mountains are believed to have formed as a result of tectonic events.[121]

The concentration of maria on the near side likely reflects the substantially thicker crust of the highlands of the Far Side, which may have formed in a slow-velocity impact of a second moon of Earth a few tens of millions of years after the Moon's formation.[122][123] Alternatively, it may be a consequence of asymmetrical tidal heating when the Moon was much closer to the Earth.[124]

A major geologic process that has affected the Moon's surface is impact cratering,[125] with craters formed when asteroids and comets collide with the lunar surface. There are estimated to be roughly 300,000 craters wider than 1km (0.6mi) on the Moon's near side.[126] The lunar geologic timescale is based on the most prominent impact events, including Nectaris, Imbrium, and Orientale; structures characterized by multiple rings of uplifted material, between hundreds and thousands of kilometers in diameter and associated with a broad apron of ejecta deposits that form a regional stratigraphic horizon.[127] The lack of an atmosphere, weather, and recent geological processes mean that many of these craters are well-preserved. Although only a few multi-ring basins have been definitively dated, they are useful for assigning relative ages. Because impact craters accumulate at a nearly constant rate, counting the number of craters per unit area can be used to estimate the age of the surface.[127] The radiometric ages of impact-melted rocks collected during the Apollo missions cluster between 3.8 and 4.1billion years old: this has been used to propose a Late Heavy Bombardment period of increased impacts.[128]

High-resolution images from the Lunar Reconnaissance Orbiter in the 2010s show a contemporary crater-production rate significantly higher than was previously estimated. A secondary cratering process caused by distal ejecta is thought to churn the top two centimeters of regolith on a timescale of 81,000 years.[129][130] This rate is 100 times faster than the rate computed from models based solely on direct micrometeorite impacts.[131]

Lunar swirls are enigmatic features found across the Moon's surface. They are characterized by a high albedo, appear optically immature (i.e. the optical characteristics of a relatively young regolith), and often have a sinuous shape. Their shape is often accentuated by low albedo regions that wind between the bright swirls. They are located in places with enhanced surface magnetic fields and many are located at the antipodal point of major impacts. Well known swirls include the Reiner Gamma feature and Mare Ingenii. They are hypothesized to be areas that have been partially shielded from the solar wind, resulting in slower space weathering.[132]

Blanketed on top of the Moon's crust is a highly comminuted (broken into ever smaller particles) and impact gardened mostly gray surface layer called regolith, formed by impact processes. The finer regolith, the lunar soil of silicon dioxide glass, has a texture resembling snow and a scent resembling spent gunpowder.[133] The regolith of older surfaces is generally thicker than for younger surfaces: it varies in thickness from 1015m (3349ft) in the highlands and 45m (1316ft) in the maria.[134]

Beneath the finely comminuted regolith layer is the megaregolith, a layer of highly fractured bedrock many kilometers thick.[135]

Liquid water cannot persist on the lunar surface. When exposed to solar radiation, water quickly decomposes through a process known as photodissociation and is lost to space. However, since the 1960s, scientists have hypothesized that water ice may be deposited by impacting comets or possibly produced by the reaction of oxygen-rich lunar rocks, and hydrogen from solar wind, leaving traces of water which could possibly persist in cold, permanently shadowed craters at either pole on the Moon.[136][137] Computer simulations suggest that up to 14,000km2 (5,400sqmi) of the surface may be in permanent shadow.[83] The presence of usable quantities of water on the Moon is an important factor in rendering lunar habitation as a cost-effective plan; the alternative of transporting water from Earth would be prohibitively expensive.[138]

In years since, signatures of water have been found to exist on the lunar surface.[139] In 1994, the bistatic radar experiment located on the Clementine spacecraft, indicated the existence of small, frozen pockets of water close to the surface. However, later radar observations by Arecibo, suggest these findings may rather be rocks ejected from young impact craters.[140] In 1998, the neutron spectrometer on the Lunar Prospector spacecraft showed that high concentrations of hydrogen are present in the first meter of depth in the regolith near the polar regions.[141] Volcanic lava beads, brought back to Earth aboard Apollo 15, showed small amounts of water in their interior.[142]

The 2008 Chandrayaan-1 spacecraft has since confirmed the existence of surface water ice, using the on-board Moon Mineralogy Mapper. The spectrometer observed absorption lines common to hydroxyl, in reflected sunlight, providing evidence of large quantities of water ice, on the lunar surface. The spacecraft showed that concentrations may possibly be as high as 1,000ppm.[143] Using the mapper's reflectance spectra, indirect lighting of areas in shadow confirmed water ice within 20 latitude of both poles in 2018.[144] In 2009, LCROSS sent a 2,300kg (5,100lb) impactor into a permanently shadowed polar crater, and detected at least 100kg (220lb) of water in a plume of ejected material.[145][146] Another examination of the LCROSS data showed the amount of detected water to be closer to 15512kg (34226lb).[147]

In May 2011, 6151410 ppm water in melt inclusions in lunar sample 74220 was reported,[148] the famous high-titanium "orange glass soil" of volcanic origin collected during the Apollo 17 mission in 1972. The inclusions were formed during explosive eruptions on the Moon approximately 3.7 billion years ago. This concentration is comparable with that of magma in Earth's upper mantle. Although of considerable selenological interest, this insight does not mean that water is easily available since the sample originated many kilometers below the surface, and the inclusions are so difficult to access that it took 39 years to find them with a state-of-the-art ion microprobe instrument.

Analysis of the findings of the Moon Mineralogy Mapper (M3) revealed in August 2018 for the first time "definitive evidence" for water-ice on the lunar surface.[149][150] The data revealed the distinct reflective signatures of water-ice, as opposed to dust and other reflective substances.[151] The ice deposits were found on the North and South poles, although it is more abundant in the South, where water is trapped in permanently shadowed craters and crevices, allowing it to persist as ice on the surface since they are shielded from the sun.[149][151]

In October 2020, astronomers reported detecting molecular water on the sunlit surface of the Moon by several independent spacecraft, including the Stratospheric Observatory for Infrared Astronomy (SOFIA).[152][153][154][155]

The Earth and the Moon form the Earth-Moon satellite system with a shared center of mass, or barycentre. This barycentre stays located at all times 1,700km (1,100mi) (about a quarter of Earth's radius) beneath the Earth's surface, making the Moon seemingly orbit the Earth.

The orbital eccentricity, giving ovalness of the orbit, is 0.055.[1]The Lunar distance, or the semi-major axis of the geocentric lunar orbit, is approximately 400,000km, which is a quarter of a million miles or 1.28 light-seconds, and a unit of measure in astronomy. This is not to be confused with the instantaneous EarthMoon distance, or distance to the Moon, the momentanous distance from the center of Earth to the center of the Moon.

The Moon makes a complete orbit around Earth with respect to the fixed stars, its sidereal period, about once every 27.3days,[h]. However, because the Earth-Moon system moves at the same time in its orbit around the Sun, it takes slightly longer, 29.5days;[i],[60] to return at the same lunar phase, completing a full cycle, as seen from Earth. This synodic period or synodic month is commonly known as the lunar month and is equal to the length of the solar day on the Moon.[156]

Due to tidal locking, the Moon has a 1:1 spinorbit resonance. This rotationorbit ratio makes the Moon's orbital periods around Earth equal to its corresponding rotation periods. This is the reason for only one side of the Moon, its so-called near side, being visible from Earth. That said, while the movement of the Moon is in resonance, it still is not without nuances such as libration, resulting in slightly changing perspectives, making over time and location on Earth about 59% of the Moon's surface visible from Earth.[157]

Unlike most satellites of other planets, the Moon's orbital plane is closer to the ecliptic plane than to the planet's equatorial plane. The Moon's orbit is subtly perturbed by the Sun and Earth in many small, complex and interacting ways. For example, the plane of the Moon's orbit gradually rotates once every 18.61years,[158] which affects other aspects of lunar motion. These follow-on effects are mathematically described by Cassini's laws.[159]

The gravitational attraction that Earth and the Moon (as well as the Sun) exert on each other manifests in a slightly greater attraction on the sides of closest to each other, resulting in tidal forces. Ocean tides are the most widely experienced result of this, but tidal forces considerably affect also other mechanics of Earth, as well as the Moon and their system.

The lunar solid crust experiences tides of around 10cm (4in) amplitude over 27days, with three components: a fixed one due to Earth, because they are in synchronous rotation, a variable tide due to orbital eccentricity and inclination, and a small varying component from the Sun.[160] The Earth-induced variable component arises from changing distance and libration, a result of the Moon's orbital eccentricity and inclination (if the Moon's orbit were perfectly circular and un-inclined, there would only be solar tides).[160] According to recent research, scientists suggest that the Moon's influence on the Earth may contribute to maintaining Earth's magnetic field.[161]

The cumulative effects of stress built up by these tidal forces produces moonquakes. Moonquakes are much less common and weaker than are earthquakes, although moonquakes can last for up to an hour significantly longer than terrestrial quakes because of scattering of the seismic vibrations in the dry fragmented upper crust. The existence of moonquakes was an unexpected discovery from seismometers placed on the Moon by Apollo astronauts from 1969 through 1972.[162]

The most commonly known effect of tidal forces are elevated sea levels called ocean tides.[163] While the Moon exerts most of the tidal forces, the Sun also exerts tidal forces and therefore contributes to the tides as much as 40% of the Moon's tidal force; producing in interplay the spring and neap tides.[163]

The tides are two bulges in the Earth's oceans, one on the side facing the Moon and the other on the side opposite. As the Earth rotates on its axis, one of the ocean bulges (high tide) is held in place "under" the Moon, while another such tide is opposite. As a result, there are two high tides, and two low tides in about 24 hours.[163] Since the Moon is orbiting the Earth in the same direction of the Earth's rotation, the high tides occur about every 12 hours and 25 minutes; the 25 minutes is due to the Moon's time to orbit the Earth.

If the Earth were a water world (one with no continents) it would produce a tide of only one meter, and that tide would be very predictable, but the ocean tides are greatly modified by other effects:

As a result, the timing of the tides at most points on the Earth is a product of observations that are explained, incidentally, by theory.

Delays in the tidal peaks of both ocean and solid-body tides cause torque in opposition to the Earth's rotation. This "drains" angular momentum and rotational kinetic energy from Earth's rotation, slowing the Earth's rotation.[163][160] That angular momentum, lost from the Earth, is transferred to the Moon in a process known as tidal acceleration, which lifts the Moon into a higher orbit while lowering orbital speed around the Earth.

Thus the distance between Earth and Moon is increasing, and the Earth's rotation is slowing in reaction.[160] Measurements from laser reflectors left during the Apollo missions (lunar ranging experiments) have found that the Moon's distance increases by 38mm (1.5in) per year (roughly the rate at which human fingernails grow).[165][166][167]Atomic clocks show that Earth's day lengthens by about 17microseconds every year,[168][169][170] slowly increasing the rate at which UTC is adjusted by leap seconds.

This tidal drag makes the rotation of Earth and the orbital period of the Moon very slowly match. This matching first results in tidally locking the lighter body of the orbital system, as already the case with the Moon. Eventually, after 50 billion years,[171] also the Earth would be made to always face the Moon with the same side. This would complete the mutual tidal locking of Earth and the Moon, matching the length of Earth's day to the then also significantly increased lunar month and the Moon's day, and suspending the Moon over one meridian (comparable to the Pluto-Charon system). However, the Sun will become a red giant engulfing the Earth-Moon system long before the latter occurs.[172][173]

The tidally locked synchronous rotation of the Moon as it orbits the Earth results in it always keeping nearly the same face turned towards the planet. The side of the Moon that faces Earth is called the near side, and the opposite the far side. The far side is often inaccurately called the "dark side", but it is in fact illuminated as often as the near side: once every 29.5 Earth days. During dark moon to new moon, the near side is dark.[174]

The Moon originally rotated at a faster rate, but early in its history its rotation slowed and became tidally locked in this orientation as a result of frictional effects associated with tidal deformations caused by Earth.[175] With time, the energy of rotation of the Moon on its axis was dissipated as heat, until there was no rotation of the Moon relative to Earth. In 2016, planetary scientists using data collected on the 1998-99 NASA Lunar Prospector mission, found two hydrogen-rich areas (most likely former water ice) on opposite sides of the Moon. It is speculated that these patches were the poles of the Moon billions of years ago before it was tidally locked to Earth.[176]

The Moon's highest altitude at culmination varies by its lunar phase, or more correctly its orbital position, and time of the year, or more correctly the position of the Earth's axis. The full moon is highest in the sky during winter and lowest during summer (for each hemisphere respectively), with its altitude changing towards dark moon to the opposite.

At the North and South Poles the Moon is 24 hours above the horizon for two weeks every tropical month (about 27.3 days), comparable to the polar day of the tropical year. Zooplankton in the Arctic use moonlight when the Sun is below the horizon for months on end.[177]

The apparent orientation of the Moon depends on its position in the sky and the hemisphere of the Earth from which it is being viewed. In the northern hemisphere it is seen upside down compared to the view in the southern hemisphere.[178] Sometimes the "horns" of a crescent moon appear to be pointing more upwards than sideways. This phenomenon is called a wet moon and occurs more frequently in the tropics.[179]

The distance between the Moon and Earth varies from around 356,400km (221,500mi) to 406,700km (252,700mi) at perigee (closest) and apogee (farthest), respectively, making the Moon's apparent size fluctuate. On sverage the Moon's angular diameter is about 0.52 (on average) in the sky, roughly the same apparent size as the Sun (see Eclipses). Additionally when close to the horizon a purely psychological effect, known as the Moon illusion, makes the Moon appear larger.[180]

Despite the Moon's tidal locking, the effect of libration makes about 59% of the Moon's surface visible from Earth over the course of one month.[157][60]

The Moon has an exceptionally low albedo, giving it a reflectance that is slightly brighter than that of worn asphalt. Despite this, it is the brightest object in the sky after the Sun.[60][j] This is due partly to the brightness enhancement of the opposition surge; the Moon at quarter phase is only one-tenth as bright, rather than half as bright, as at full moon.[181] Additionally, color constancy in the visual system recalibrates the relations between the colors of an object and its surroundings, and because the surrounding sky is comparatively dark, the sunlit Moon is perceived as a bright object. The edges of the full moon seem as bright as the center, without limb darkening, because of the reflective properties of lunar soil, which retroreflects light more towards the Sun than in other directions. The Moon's color depends on the light the Moon reflects, which in turn depends on the Moon's surface and its features, having for example large darker regions. In general the lunar surface reflects a brown-tinged gray light.[182]

Viewed from Earth the air filters the reflected light, at times giving it a red colour depending on the angle of the Moon in the sky and thickness of the atmosphere, or a blue tinge depending on the particles in the air,[182] as in cases of volcanic particles.[183] The terms blood moon and blue moon do not necessarily refer to circumstances of red or blue moonlight, but are rather particular cultural references such as particular full moons of a year.

There has been historical controversy over whether observed features on the Moon's surface change over time. Today, many of these claims are thought to be illusory, resulting from observation under different lighting conditions, poor astronomical seeing, or inadequate drawings. However, outgassing does occasionally occur and could be responsible for a minor percentage of the reported lunar transient phenomena. Recently, it has been suggested that a roughly 3km (1.9mi) diameter region of the lunar surface was modified by a gas release event about a million years ago.[184][185]

Half of the Moon's surface is always illuminated by the Sun (except during a lunar eclipse). Earth also reflects light onto the Moon, observable at times as Earthlight when it is again reflected back to Earth from areas of the near side of the Moon that are not illuminated by the Sun.

With the different positions of the Moon, different areas of it are illuminated by the Sun. This illumination of different lunar areas, as viewed from Earth, produces the different lunar phases during the synodic month. A phase is equal to the area of the visible lunar sphere that is illuminated by the Sun. This area or degree of illumination is given by ( 1 cos e ) / 2 = sin 2 ( e / 2 ) {displaystyle (1-cos e)/2=sin ^{2}(e/2)} , where e {displaystyle e} is the elongation (i.e., the angle between Moon, the observer on Earth, and the Sun).

On 14 November 2016, the Moon was at full phase closer to Earth than it had been since 1948. It was 14% closer and larger than its farthest position in apogee.[187] This closest point coincided within an hour of a full moon, and it was 30% more luminous than when at its greatest distance because of its increased apparent diameter, which made it a particularly notable example of a "supermoon".[188][189][190]

At lower levels, the human perception of reduced brightness as a percentage is provided by the following formula:[191][192]

When the actual reduction is 1.00 / 1.30, or about 0.770, the perceived reduction is about 0.877, or 1.00 / 1.14. This gives a maximum perceived increase of 14% between apogee and perigee moons of the same phase.[193]

Eclipses only occur when the Sun, Earth, and Moon are all in a straight line (termed "syzygy"). Solar eclipses occur at new moon, when the Moon is between the Sun and Earth. In contrast, lunar eclipses occur at full moon, when Earth is between the Sun and Moon. The apparent size of the Moon is roughly the same as that of the Sun, with both being viewed at close to one-half a degree wide. The Sun is much larger than the Moon but it is the vastly greater distance that gives it the same apparent size as the much closer and much smaller Moon from the perspective of Earth. The variations in apparent size, due to the non-circular orbits, are nearly the same as well, though occurring in different cycles. This makes possible both total (with the Moon appearing larger than the Sun) and annular (with the Moon appearing smaller than the Sun) solar eclipses.[194] In a total eclipse, the Moon completely covers the disc of the Sun and the solar corona becomes visible to the naked eye. Because the distance between the Moon and Earth is very slowly increasing over time,[163] the angular diameter of the Moon is decreasing. As it evolves toward becoming a red giant, the size of the Sun, and its apparent diameter in the sky, are slowly increasing.[k] The combination of these two changes means that hundreds of millions of years ago, the Moon would always completely cover the Sun on solar eclipses, and no annular eclipses were possible. Likewise, hundreds of millions of years in the future, the Moon will no longer cover the Sun completely, and total solar eclipses will not occur.[195]

Because the Moon's orbit around Earth is inclined by about 5.145 (5 9') to the orbit of Earth around the Sun, eclipses do not occur at every full and new moon. For an eclipse to occur, the Moon must be near the intersection of the two orbital planes.[196] The periodicity and recurrence of eclipses of the Sun by the Moon, and of the Moon by Earth, is described by the saros, which has a period of approximately 18years.[197]

Because the Moon continuously blocks the view of a half-degree-wide circular area of the sky,[l][198] the related phenomenon of occultation occurs when a bright star or planet passes behind the Moon and is occulted: hidden from view. In this way, a solar eclipse is an occultation of the Sun. Because the Moon is comparatively close to Earth, occultations of individual stars are not visible everywhere on the planet, nor at the same time. Because of the precession of the lunar orbit, each year different stars are occulted.[199]

It is believed by some that 2030,000 year old tally sticks, were used to observe the phases of the Moon, keeping time using the waxing and waning of the Moon's phases.[200]One of the earliest-discovered possible depictions of the Moon is a 5000-year-old rock carving Orthostat 47 at Knowth, Ireland.[201][202]

The ancient Greek philosopher Anaxagoras (d.428 BC) reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former.[203][204]:227 Elsewhere in the 5th century BC to 4th century BC, Babylonian astronomers had recorded the 18-year Saros cycle of lunar eclipses,[205] and Indian astronomers had described the Moon's monthly elongation.[206] The Chinese astronomer Shi Shen (fl. 4th century BC) gave instructions for predicting solar and lunar eclipses.[204]:411

In Aristotle's (384322BC) description of the universe, the Moon marked the boundary between the spheres of the mutable elements (earth, water, air and fire), and the imperishable stars of aether, an influential philosophy that would dominate for centuries.[207] Archimedes (287212 BC) designed a planetarium that could calculate the motions of the Moon and other objects in the Solar System.[208] In the 2nd century BC, Seleucus of Seleucia correctly theorized that tides were due to the attraction of the Moon, and that their height depends on the Moon's position relative to the Sun.[209] In the same century, Aristarchus computed the size and distance of the Moon from Earth, obtaining a value of about twenty times the radius of Earth for the distance.

Although the Chinese of the Han Dynasty believed the Moon to be energy equated to qi, their 'radiating influence' theory recognized that the light of the Moon was merely a reflection of the Sun, and Jing Fang (7837BC) noted the sphericity of the Moon.[204]:413414 Ptolemy (90168AD) greatly improved on the numbers of Aristarchus, calculating the values of a mean distance of 59times Earth's radius and a diameter of 0.292Earth diameters were close to the correct values of about 60 and 0.273 respectively.[210] In the 2nd century AD, Lucian wrote the novel A True Story, in which the heroes travel to the Moon and meet its inhabitants. In 499AD, the Indian astronomer Aryabhata mentioned in his Aryabhatiya that reflected sunlight is the cause of the shining of the Moon.[211] The astronomer and physicist Alhazen (9651039) found that sunlight was not reflected from the Moon like a mirror, but that light was emitted from every part of the Moon's sunlit surface in all directions.[212] Shen Kuo (10311095) of the Song dynasty created an allegory equating the waxing and waning of the Moon to a round ball of reflective silver that, when doused with white powder and viewed from the side, would appear to be a crescent.[204]:415416

During the Middle Ages, before the invention of the telescope, the Moon was increasingly recognised as a sphere, though many believed that it was "perfectly smooth".[213]

In 1609, Galileo Galilei used an early telescope to make drawings of the Moon for his book Sidereus Nuncius, and deduced that it was not smooth but had mountains and craters. Thomas Harriot had made, but not published such drawings a few months earlier.

Telescopic mapping of the Moon followed: later in the 17th century, the efforts of Giovanni Battista Riccioli and Francesco Maria Grimaldi led to the system of naming of lunar features in use today. The more exact 18341836 Mappa Selenographica of Wilhelm Beer and Johann Heinrich Mdler, and their associated 1837 book Der Mond, the first trigonometrically accurate study of lunar features, included the heights of more than a thousand mountains, and introduced the study of the Moon at accuracies possible in earthly geography.[214] Lunar craters, first noted by Galileo, were thought to be volcanic until the 1870s proposal of Richard Proctor that they were formed by collisions.[60] This view gained support in 1892 from the experimentation of geologist Grove Karl Gilbert, and from comparative studies from 1920 to the 1940s,[215] leading to the development of lunar stratigraphy, which by the 1950s was becoming a new and growing branch of astrogeology.[60]

After World War II the first launch systems were developed and by the end of the 1950s they reached capabilities that allowed the Soviet Union and the United States to launch spacecrafts into space. The Cold War fueled a closely followed development of launch systems by the two states, resulting in the so-called Space Race and its later phase the Moon Race, accelerating efforts and interest in exploration of the Moon.

After the first spaceflight of Sputnik 1 in 1957 during International Geophysical Year the spacecrafts of the Soviet Union's Luna program were the first to accomplish a number of goals. Following three unnamed failed missions in 1958,[216] the first human-made object Luna 1 escaped Earth's gravity and passed near the Moon in 1959. Later that year the first human-made object Luna 2 reached the Moon's surface by intentionally impacting. By the end of the year Luna 3 reached as the first human-made object the normally occluded far side of the Moon, taking the first photographs of it.The first spacecraft to perform a successful lunar soft landing was Luna 9 and the first vehicle to orbit the Moon was Luna 10, both in 1966.[60]

Following President John F. Kennedy's 1961 commitment to a manned Moon landing before the end of the decade, the United States, under NASA leadership, launched a series of uncrewed probes to develop an understanding of the lunar surface in preparation for human missions: the Jet Propulsion Laboratory's Ranger program, the Lunar Orbiter program and the Surveyor program. The crewed Apollo program was developed in parallel; after a series of uncrewed and crewed tests of the Apollo spacecraft in Earth orbit, and spurred on by a potential Soviet lunar human landing, in 1968 Apollo 8 made the first human mission to lunar orbit. The subsequent landing of the first humans on the Moon in 1969 is seen by many as the culmination of the Space Race.[217]

Neil Armstrong became the first person to walk on the Moon as the commander of the American mission Apollo 11 by first setting foot on the Moon at 02:56UTC on 21 July 1969.[218] An estimated 500million people worldwide watched the transmission by the Apollo TV camera, the largest television audience for a live broadcast at that time.[219][220] The Apollo missions 11 to 17 (except Apollo 13, which aborted its planned lunar landing) removed 380.05 kilograms (837.87lb) of lunar rock and soil in 2,196 separate samples.[221]

Scientific instrument packages were installed on the lunar surface during all the Apollo landings. Long-lived instrument stations, including heat flow probes, seismometers, and magnetometers, were installed at the Apollo 12, 14, 15, 16, and 17 landing sites. Direct transmission of data to Earth concluded in late 1977 because of budgetary considerations,[222][223] but as the stations' lunar laser ranging corner-cube retroreflector arrays are passive instruments, they are still being used.[224]Apollo 17 in 1972 remains the last crewed mission to the Moon. Explorer 49 in 1973 was the last dedicated U.S. probe to the Moon until the 1990s.

The Soviet Union continued sending robotic missions to the Moon until 1976, deploying in 1970 with Luna 17 the first remote controlled rover Lunokhod 1 on an extraterrestrial surface, and collecting and returning 0.3kg of rock and soil samples with three Luna sample return missions (Luna 16 in 1970, Luna 20 in 1972, and Luna 24 in 1976).[225]

A near lunar quietude of fourteen years followed the last Soviet mission to the Moon of 1976. Astronautics had shifted its focus towards the exploration of the inner (e.g. Venera program) and outer (e.g. Pioneer 10, 1972) Solar System planets, but also towards Earth orbit, developing and continuously operating, beside communication satellites, Earth observation satellites (e.g. Landsat program, 1972) space telescopes and particularly space stations (e.g. Salyut program, 1971).

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1. Artemis is our first step toward space colonization  Big Think
2. Equilibrium/Sustainability Artemis launch aims at sustainable lunar base  The Hill
3. With Artemis, NASA envisions a multiplanetary future for humanity  The Christian Science Monitor
4. NASA Launches Artemis 1, Third Moon Landing to Come  Nasdaq
5. Live Updates: See the first photos of Earth from NASA's moon-bound Orion spacecraft  Yahoo! Voices
6. View Full Coverage on Google News

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Full or new moon which appears larger due to coinciding with perigee

A supermoon is a full moon or a new moon that nearly coincides with perigeethe closest that the Moon comes to the Earth in its elliptic orbitresulting in a slightly larger-than-usual apparent size of the lunar disk as viewed from Earth.[1] The technical name is a perigee syzygy (of the EarthMoonSun system) or a full (or new) Moon around perigee.[a] Because the term supermoon is astrological in origin, it has no precise astronomical definition.[2]

The real association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like earthquakes and volcanic eruptions, but no such link has been found.[3]

The opposite phenomenon, an apogee syzygy or a full (or new) Moon around apogee, has been called a micromoon.[4]

The term supermoon is attributed to astrologer Richard Nolle while reading "Strategic Role Of Perigean spring tides in Nautical History and Coastal flooding" published in 1976 by NOAA Hydrologist Fergus Wood.[5][6][7] In practice, there is no official or even consistent definition of how near perigee the full Moon must occur to receive the supermoon label, and new moons rarely receive a supermoon label.

Nolle described the concept in a 1979 edition of Dell Horoscope including both full and new moons, but has never outlined why he chose 90% nor has provided a definitive formula for determining if a given full or new moon is "super". The basic 1979 definition read:[2]

... a new or full moon which occurs with the Moon at or near (within 90% of) its closest approach to Earth in a given orbit (perigee). In short, Earth, Moon and Sun are all in a line, with Moon in its nearest approach to Earth.

Nolle amended his definition in 2000 specifying the distance of a given full or new moon be judged against 90% of the mean distance of perigees. Nolle (incorrectly) referenced

A SuperMoon is a perigee-syzygy, a new or full moon (syzygy) which occurs when the Moon is at 90% or greater of its mean closest approach to Earth (perigee).

In 2011, Nolle added apogees to consideration explaining that he based calculations on 90% of the difference in lunar apsis extremes for the solar year. EarthSky analyzed Nolle's tables and described the updated definition as a full or new moon is considered a supermoon if l d s l d p + 0.1 ( l d a l d p ) {displaystyle ld_{s}leq ld_{p}+0.1*(ld_{a}-ld_{p})} where l d s {displaystyle ld_{s}} is the lunar distance at syzygy, l d a {displaystyle ld_{a}} is the lunar distance at apogee, and l d p {displaystyle ld_{p}} is the lunar distance at perigee. Nolle based those the mean apsis extremes referencing (incorrectly) the Wikipedia article on the subject arriving at: [10][11]

any lunation closer than 368,630 km. = SuperMoon.

Nolle also added the concept of extreme supermoon in 2000 describing the concept as any new or full moons that are at "100% or greater of the mean perigee".[9]

The term perigee-syzygy or perigee full/new moon is preferred in the scientific community.[12] Perigee is the point at which the Moon is closest in its orbit to the Earth, and syzygy is when the Earth, the Moon and the Sun are aligned, which happens at every full or new moon. Astrophysicist Fred Espenak uses Nolle's definition but preferring the label of full Moon at perigee on full moons occurring "within 90% of its closest approach to Earth in a given orbit" over Nolle's calculations based on the closest of all orbits during the solar year.[13] Wood used the definition of a full or new moon occurring within 24 hours of perigee and also used the label perigee-syzygy.[7]

Sky and Telescope magazine chose a definition of 223,000 miles (358,884km).[14]

TimeandDate.com prefers a definition of 360,000 kilometres (223,694mi).[15]

EarthSky uses Nolle's definition comparing their calculations to tables published by Nolle in 2000.[10][9]

Wood also coined the less used term proxigee where perigee and the full or new moon are separated by 10 hours or less.[7]

Of the possible 12 or 13 full (or new) moons each year, usually three or four may be classified as supermoons, as commonly defined.

The most recent full supermoon occurred on August 12, 2022, and the next one will be on July 3, 2023.[13]

The supermoon of November 14, 2016, was the closest full occurrence since January 26, 1948, and will not be surpassed until November 25, 2034.[16]

The closest full supermoon of the 21st century will occur on December 6, 2052.[17]

The oscillating nature of the distance to the full or new moon is due to the difference between the synodic and anomalistic months.[13] The period of this oscillation is about 14 synodic months, which is close to 15 anomalistic months. So every 14 lunations there is a Full Moon nearest to perigee.

Occasionally, a supermoon coincides with a total lunar eclipse. The most recent occurrence of this was in May 2022, and the next occurrence will be in October 2032.[13]

A full moon at perigee appears roughly 14% larger in diameter than at apogee.[18] Many observers insist that the moon looks bigger to them. This is likely due to observations shortly after sunset when the moon is near the horizon and the moon illusion is at its most apparent.[19]

While the moon's surface luminance remains the same, because it is closer to the earth the illuminance is about 30% brighter than at its farthest point, or apogee. This is due to the inverse square law of light which changes the amount of light received on earth in inverse proportion to the distance from the moon.[20] A supermoon directly overhead could provide up to 0.36 lux.[21]

Claims that supermoons can cause natural disasters, and the claim of Nolle that supermoons cause "geophysical stress", have been refuted by scientists.[2][22][23][24]

Despite lack of scientific evidence, there has been media speculation that natural disasters, such as the 2011 Thoku earthquake and tsunami and the 2004 Indian Ocean earthquake and tsunami, are causally linked with the 12-week period surrounding a supermoon.[25] A large, 7.5 magnitude earthquake centred 15 km north-east of Culverden, New Zealand at 00:03 NZDT on November 14, 2016, also coincided with a supermoon.[26][27]Tehran earthquake on May 8, 2020, also coincided with a supermoon.

Scientists have confirmed that the combined effect of the Sun and Moon on the Earth's oceans, the tide,[28] is greatest when the Moon is either new or full.[29] and that during lunar perigee, the tidal force is somewhat stronger,[30] resulting in perigean spring tides. However, even at its most powerful, this force is still relatively weak,[31] causing tidal differences of inches at most.[32]

Total lunar eclipses which fall on supermoon and micromoon days are relatively rare. In the 21st century, there are 87 total lunar eclipses, of which 28 are supermoons and 6 are micromoons. Almost all total lunar eclipses in Lunar Saros 129 are micromoon eclipses. An example of a supermoon lunar eclipse is the September 2015 lunar eclipse.

Annular solar eclipses occur when the Moon's apparent diameter is smaller than the Sun's. Almost all annular solar eclipses between 1880 and 2060 in Solar Saros 144 and almost all annular solar eclipses between 1940 and 2120 in Solar Saros 128 are micromoon annular solar eclipses.[33]

Media related to Supermoon at Wikimedia Commons

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On October 13, 2021, the nonagenarian and popular culture icon William Shatner went to the place where his TV character, Captain Kirk, spent much of his time: Space. He was sent there by a craft designed by Jeff Bezos's space company Blue Origin. The whole business was billed as the moment that the imagination (the leader of the fictional USS Enterprise) touched (in a manner that had the same grandeur as The Creation of Adam) the unbelievably vast reality (and possible opportunities) of outer space. A major part of what early 20th-century German sociologist Max Weber called the "spirit of capitalism" was vividly revived to the citizens of a world globalized by what the Turkish-born American economist Dani Rodrik named "capitalism 3.0." What could go wrong?

When Star Trek first aired in 1966, thanks to the determination of Lucille Ball, the Soviet Union had already launched the first human, Yuri Gagarin, into space and the US was soon to land humans on the moon. But these 20th-century extraterrestrial explorations were funded and developed by the state, and so represented a form of capitalism (2.0) that emerged in the 1930s, a capitalism planned and managed by Big Government. This new economic system connected the US and the USSR. As key members of the Frankfurt School determined in 1941, both had huge budgets and formulated "a general plan [that compelled] its fulfillment." Shatner's trip returned the Schumpeterian figure eliminated by private and public technostructures to the center of the religion of progress, the entrepreneur (capitalism 1.0).

But what did Shatner experience when he went to space? Nothing but nothingness. His words, which are taken from his new book, Boldly Go: Reflections on a Life of Awe and Wonder:

I continued my self-guided tour and turned my head to face the other direction, to stare into space. I love the mystery of the universe. I love all the questions that have come to us over thousands of years of exploration and hypotheses. Stars exploding years ago, their light traveling to us years later; black holes absorbing energy; satellites showing us entire galaxies in areas thought to be devoid of matter entirely all of that has thrilled me for years but when I looked in the opposite direction, into space, there was no mystery, no majestic awe to behold . . . all I saw was death.

His trip to space "was supposed to be a celebration; instead, it felt like a funeral," and not because he is an old mana man, who unlike young people, has no illusions about his mortality, who goes to sleep with no certainty that he will wake up, and if he does wake up, feels surprised that has lived for so long. No. That was not the source of his existential dread. It was instead the shuttle's view of all there is right next to all that it's not and can never be or become. There's really nothing out there for us. Everything that will ever and can happen is on "the warm nurturing of Earth below..."

I'm sure Jeff Bezos, one of the emperors of capitalism 3.0 (also known as neoliberalism), did not expect this negative response from Captain Kirk, but socialist and social democratic states of capitalism 2.0 did not abandon human space travel in the 1970s for no good reason. They really found not much out there for us. Space belonged to Sputnik (communication robots), not to Gagarin (colonization).

As for the moon, which on these clear September nights can be seen crossing Seattle's sky with Jupiter? Can we do anything with our nearest celestial neighbor? The men sent there in the late-'60s and early '70s discovered lots of dust. It's just everywhere, get's into everything, and, if given the chance, will drive you mad. Selenographers call this the moon's "dirty secret." The Apollo astronauts could not stop talking about how the moon "was dust, dust, dust." And this wasn't the kind of dust we find floating through the sunlight in our grounded houses, much of which is alive and carrying microbial life. Moondust, which looks like sharp shards of glass, is as dead as the space William Shatner saw through Bezos' windows.

Let's conclude this rather bleak post, and bleak not because space is, as Shatner saw, almost entirely a "cold, dark, black emptiness," but because "every day, we are confronted with the knowledge of further destruction of Earth [AKA All There Is] at our hands," with Brian Eno's ethereal "An Ending (Ascent)"?

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A We'koqma'q First nation clothing designer has outfitted a new clothing bank in her home community to help other peopleconnect with their Mi'kmaw culture.

Miranda Gould began creating ribbon skirts almost 30 years ago, after attending ceremonies with women who were wearing them.

The 49-year-old said her early creations were limited to a specific design, but now she creates all kinds of patterns on the floor-length garments adorned withbrightly coloured bands of ribbon.

"It's what makes you happy," Gould said. "Everyone carries an aura, or an energy, and colours that make them happy."

Ribbon skirts date back to North America's colonial past when Indigenous women used ribbons brought from Europe to decorate their clothing, usually around the hemline.

The skirts are often worn at powwows, weddings, graduations and other special events and ceremonies. Many people who wear the skirts will personalize themwith patterns and colours that mean something to them ortheir family.

Gould, who showcasedmany of her designs at a recent Indigenous fashion show in Membertou, said many people are now wearing ribbonskirts as everyday clothing. She saidtraditional teachings help explain why so many Indigenous women started wearing skirts as a garment of choice.

"You're a life giver," she said."We bear children and you allow that energy to flow from Mother Earth to your womb as a sign of respect in that connection to Mother Earth. And so when you wear your skirt, you walk in honour of life."

The We'koqma'q band council created the clothing bank after hearing from people who didn't have the right clothing for the ceremonies.

Chief Annie Bernard-Daisley says she was inspired by the Native Women's Association in Millbrook, which operates a similar clothing bank.

"We even had some people that needed a ribbon shirt for a funeral and they didn't have one," said Bernard-Daisley.

"It's a beautiful, beautiful initiative."

Bernard-Daisley said it's touching to see the tradition return after it was almost quashed by the impacts of colonization and Canada's residential school system.

She said there is a growing trend of people taking part in traditions such as pipe ceremonies, sweat lodgesor grandmother moon rituals.

"Ceremony, it helps you and it grounds you and it just sometimes takes some weight off you, off your shoulders," Bernard-Daisley said.

"It's up to us as leaders to enhance and to promote that and to support that initiative and to take part in [ceremonies] as well."

In total, 25 ribbon skirts and three shirts were finished last week for the We'koqma'q clothing bank program.

People who want to borrow a ribbon skirt or shirt must sign them out at the We'koqma'q elder's centre, and return them, so they can be loaned to others.

Gouldspent a whole month on her creations and is proud that they will connect her people to their culture.

"It's a sense of accomplishment in the work that I have tried to achieve in my lifetime," she said.

"And to leave a legacy like that is very honourable for me."

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The stakes, tensions, and cost of victory are high in an edge-of-your-seat episode of Star Wars: Andor. The episode was a serious nail-biter as the rebels of Aldhani finally execute the plan thats been building up for two episodes, all amid the stunning spectacle of a celestial phenomenon. (Warning: SPOILERS ahead for Andor episode 6, The Eye)

The episode opens with Nemik (Alex Lawther) talking to Cassian (Diego Luna) about his nerves ahead of the mission. Its another chance to talk about Nemiks manifesto, which he adds to when he cant sleep, and how mercenaries like Clem fit into his thoughts about rebellion.

Theres a bit of foreshadowinghere about Nemik, who will literally be crushed to death by rolls of credits. Nemiks death highlights the sad reality of what often happens to fighters who rebel for the right reasons and not just for money.

As the crew leaves Aldhani in the transport ship, Skeen (Ebon Moss-Bachrach ) appears just as desperate to save Nemik as leader Vel (Faye Marsay). He implores Cassian to make a detour to get Nemik to a doctor. But to no ones surprise, Skeens motive for taking this detour isnt exactly selfless. As the four-armed Dr. Quadpaw (Aiden Cook) works on Nemik, Skeen offers Cassian a chance to split the haul of 80 million credits and escape to a nearby vacant moon.

He also tells Cassian that his heartfelt story about his brother last week was a lie. He is a rebel, but one who only serves himself. As a mercenary hired by Luthen (Stellan Skarsgrd), Cassian has something in common with him. But something snaps in Cassian and he shoots and kills Skeen with barely a moments hesitation.

When he walks into the surgery room to find Nemik dead, Cassian tries to convince Vel of Skeens plan to cut and run. Shes not buying it, but she lets him leave with Nemiks manifesto anyway. Nemik wanted Cassian to have it, which helps fuel Cassians smoldering rebellious fire.

The core of this episode is the heist in the Imperial garrison on Aldhani, a nerve-wracking 53 minutes that start seamlessly and slowly unravel because of nerves and hiccups. Ultimately, the rebels succeed,but at a heartbreaking cost: Nemik and Taramyn (Gershwyn Eustache Jnr), whom Skeen failed to cover from Imperial fire, lose their lives.

Its unclear whats next for Aldhani rebels like Vel and Cinta, who had to stay behind and blend in with the Imperials for a bit. But The Eye marks a turning point for Cassian at the halfway point of the series.

Beyond the heist, Episode 6 also has a lot of smaller moments worth mentioning. We see high-ranking officers in the Empire openly discussing their colonization efforts on Aldhani. While the Imperials put on a welcoming front as the Dhanis arrive for the pilgrimage to see The Eye, they also delight in the fact that they continue to stifle the peoples cultural practices by dwindling their numbers. And they excitedly look forward to executing their plans to forcibly take over the sacred cultural site to make more room for the garrison. The Empires view of Aldhani and of countless other systems and indigenous peoples is one of disrespect and mockery.

For the rebels, the heist is only one victory, but small victories like this will slowly help planets and peoples take back control from the Empire. All of this is underlined by the beautiful kaleidoscope of celestial colors shooting across the Aldhani sky, watched by a watery-eyed Dhani crowd as Cassian outruns TIE fighters.

The episode ends on a thrilling cliffhanger: Mon Mothma (Genevieve OReilly) tries to address the Imperial Senate while everyone checks alerts on their datapads about the rebel attack on Aldhani. Elsewhere, Luthen cackles with joy after hearing of the attacks success, and the Imperial Security Bureau scrambles to counter it.

Episode 6 is an electrifying new high for the series. May the momentum continue in Episode 7, coming out next Wednesday.

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Review: Andor Episode 6 gives a heartbreaking victory to the rebels of Aldhani - Winter is Coming

Many Americans stayed home from work and school on Monday in honor of Indigenous Peoples Day. The holiday is important to tribal leaders and community members nationwide who have long fought to safeguard Native communities.

Indigenous Peoples Day falls on the second Monday in October. It's honored in addition to, or instead of, Columbus Day by more than 130 cities, the District of Columbia and 14 states, Smithsonian Magazine reports.

Cherokee Nation Principal Chief Chuck Hoskin, Jr., told Newsweek about the holiday's significance.

"It's very meaningful to Cherokee Nation; I know that it is very meaningful for Native peoples all over the country," he said. "And increasingly, it is important to non-Natives who...recognize the need to celebrate Native heritage, look back at the history and really celebrate the future that we all have together."

Indigenous Peoples Day isn't yet an official federal holiday, but it was recognized at the federal level for the first time last year. That acknowledgment was decades in the making.

In 1977, Indigenous delegates at the United Nations conference resolved that October 12 should be observed as an "international day of solidarity with the Indigenous peoples of the Americas."

South Dakota began celebrating Native American Day back in 1990, per CNN. Two years later, the city of Berkeley, California, celebrated Indigenous Peoples' Day as a way to rail against the 500th anniversary of Columbus' voyage.

Many argue that the Italian explorer Christopher Columbus represents the colonization of Indigenous lands and the slaughter of Native communities. Hoskin told Newsweek that "honoring [Columbus] on a holiday really obscures the atrocities done under his command."

It's important to understand the facts surrounding what Columbus and other colonizers did, and the consequences of those actions, he added.

"We have to understand how to reconcile that today, and to know our history better and then to collectively do better as Americans," Hoskin continued. "And I think we can't fully do that so long as we are honoring Christopher Columbus as some sort of a great savior, because it really obscures the great damage he did to Native peoples, which is a history worthy of study and worthy of reflection."

Those looking to celebrate should start by recognizing the Indigenous lands on which they live and the original peoples who called it home, Smithsonian Magazine notes. Observers can moon- and stargaze "from a Native perspective," plus spend time outside to honor nature.

People can also support work by Indigenous creators, from podcasts like This Land by Rebecca Nagle to TV shows like Hulu's Reservation Dogs.

Hoskin encourages participants to realize that there are more than 500 tribes countrywide, each with unique stories and histories.

"We do, of course, have similar themes running through our history of dispossession, of oppression, but also a large measure of triumph here in the modern era," he said. "If Americans will think about that, that'll be helpful, because one of the problems we've had is just a lack of knowledge of our place in the history of this continent. And that lack of knowledge can lead to things like harmful federal Indian policy or state government actions that trample on Native rights."

Many social media users have commemorated the holiday on Twitter.

Secretary of the Interior Deb Haaland, who's a member of the Pueblo of Laguna tribe, posted a video outlining the work done by the administration of President Joe Biden to help Indigenous communities.

"Today we celebrate the strength of Indigenous communities, the traditions and cultures that have survived millennia, and our fervent hope for the future. Happy Indigenous Peoples' Day, everyone!" Haaland wrote in a tweet.

The White House also issued a proclamation ahead of the holiday, acknowledging that for hundreds of years, Indigenous peoples were ripped from their lands, forced to assimilate and banned from practicing sacred customs. The proclamation further noted Natives' continued contribution to the arts, scholarship, public service and the law, honoring them for "shaping the contours of this country since time immemorial."

Other advocates also commemorated the day on Twitter, including Bernice King, daughter of late civil rights leader Martin Luther King, Jr.

"I am remembering and reflecting on the sacrifice, resilience, authenticity, and erasure of Indigenous groups and tribal communities in America and across the globe," King wrote in a tweet. "We celebrate the people, stories, and cultures and commit to justice in our World House."

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National Indigenous Peoples Day 2022: Everything to Know - Newsweek