Researchers using the orbiter's ground-penetrating radar identified a large, buried deposit of frozen carbon dioxide, or dry ice, at the Red Planet's south pole. The scientists suspect that much of this carbon dioxide enters the planet's atmosphere and swells the atmosphere's mass when Mars' tilt increases. The findings are published in this week's issue of the journal Science.

The newly found deposit has a volume similar to Lake Superior's nearly 3,000 cubic miles (about 12,000 cubic kilometers). The deposit holds up to 80 percent as much carbon dioxide as today's Martian atmosphere. Collapse pits caused by dry ice sublimation and other clues suggest the deposit is in a dissipating phase, adding gas to the atmosphere each year. Mars' atmosphere is about 95 percent carbon dioxide, in contrast to Earth's much thicker atmosphere, which is less than .04 percent carbon dioxide.

"We already knew there is a small perennial cap of carbon-dioxide ice on top of the water ice there, but this buried deposit has about 30 times more dry ice than previously estimated," said Roger Phillips of Southwest Research Institute in Boulder, Colo. Phillips is deputy team leader for the Mars Reconnaissance Orbiter's Shallow Radar instrument and lead author of the report.

"We identified the deposit as dry ice by determining the radar signature fit the radio-wave transmission characteristics of frozen carbon dioxide far better than the characteristics of frozen water," said Roberto Seu of Sapienza University of Rome, team leader for the Shallow Radar and a co-author of the new report. Additional evidence came from correlating the deposit to visible sublimation features typical of dry ice.

"When you include this buried deposit, Martian carbon dioxide right now is roughly half frozen and half in the atmosphere, but at other times it can be nearly all frozen or nearly all in the atmosphere," Phillips said.

An occasional increase in the atmosphere would strengthen winds, lofting more dust and leading to more frequent and more intense dust storms. Another result is an expanded area on the planet's surface where liquid water could persist without boiling. Modeling based on known variation in the tilt of Mars' axis suggests several-fold changes in the total mass of the planet's atmosphere can happen on time frames of 100,000 years or less.

The changes in atmospheric density caused by the carbon-dioxide increase also would amplify some effects of the changes caused by the tilt. Researchers plugged the mass of the buried carbon-dioxide deposit into climate models for the period when Mars' tilt and orbital properties maximize the amount of summer sunshine hitting the south pole. They found at such times, global, year-round average air pressure is approximately 75 percent greater than the current level.

"A tilted Mars with a thicker carbon-dioxide atmosphere causes a greenhouse effect that tries to warm the Martian surface, while thicker and longer-lived polar ice caps try to cool it," said co-author Robert Haberle, a planetary scientist at NASA's Ames Research Center in Moffett Field, Calif. "Our simulations show the polar caps cool more than the greenhouse warms. Unlike Earth, which has a thick, moist atmosphere that produces a strong greenhouse effect, Mars' atmosphere is too thin and dry to produce as strong a greenhouse effect as Earth's, even when you double its carbon-dioxide content."

The Shallow Radar, one of the Mars Reconnaissance Orbiter's six instruments, was provided by the Italian Space Agency, and its operations are led by the Department of Information Engineering, Electronics and Telecommunications at Sapienza University of Rome. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter project for NASA's Science Mission Directorate at the agency's headquarters in Washington. Lockheed Martin Space Systems in Denver built the spacecraft.

For more information visit http://www.nasa.gov/mission_pages/MRO/news/mro20110421.html

"For 21 years, Hubble has profoundly changed our view of the universe, allowing us to see deep into the past while opening our eyes to the majesty and wonders around us," NASA Administrator Charles Bolden said."I was privileged to pilot space shuttle Discovery as it deployed Hubble. After all this time, new Hubble images still inspire awe and are a testament to the extraordinary work of the many people behind the world's most famous observatory."

Hubble was launched April 24, 1990, aboard Discovery's STS-31 mission. Hubble discoveries revolutionized nearly all areas of current astronomical research from planetary science to cosmology.

"Hubble is America's gift to the world," Sen. Barbara Mikulski of Maryland said. "Its jaw-dropping images have rewritten the textbooks and inspired generations of schoolchildren to study math and science. It has been documenting the history of our universe for 21 years. Thanks to the daring of our brave astronauts, a successful servicing mission in 2009 gave Hubble new life. I look forward to Hubble's amazing images and inspiring discoveries for years to come."

The newly released Hubble image shows a large spiral galaxy, known as UGC 1810, with a disk that is distorted into a rose-like shape by the gravitational tidal pull of the companion galaxy below it, known as UGC 1813. A swath of blue jewel-like points across the top is the combined light from clusters of intensely bright and hot young blue stars. These massive stars glow fiercely in ultraviolet light.

The smaller, nearly edge-on companion shows distinct signs of intense star formation at its nucleus, perhaps triggered by the encounter with the companion galaxy.

Arp 273 lies in the constellation Andromeda and is roughly 300 million light-years away from Earth. The image shows a tenuous tidal bridge of material between the two galaxies that are separated from each other by tens of thousands of light-years.

A series of uncommon spiral patterns in the large galaxy are a tell-tale sign of interaction. The large, outer arm appears partially as a ring, a feature seen when interacting galaxies actually pass through one another. This suggests the smaller companion dived deep, but off-center, through UGC 1810. The inner set of spiral arms is highly warped out of the plane, with one of the arms going behind the bulge and coming back out the other side. How these two spiral patterns connect is not precisely known.

The larger galaxy in the UGC 1810 - UGC 1813 pair has a mass about five times that of the smaller galaxy. In unequal pairs such as this, the relatively rapid passage of a companion galaxy produces the lopsided or asymmetric structure in the main spiral. Also in such encounters, the starburst activity typically begins in the minor galaxies earlier than in the major galaxies. These effects could be because the smaller galaxies have consumed less of the gas present in their nuclei, from which new stars are born.

The interaction was imaged on Dec. 17, 2010, with Hubble's Wide Field Camera 3 (WFC3). The picture is a composite of data taken with three separate filters on WFC3 that allow a broad range of wavelengths covering the ultraviolet, blue, and red portions of the spectrum.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy Inc. in Washington, D.C.

For more information visit http://www.nasa.gov/mission_pages/hubble/science/hubble-rose.html

"I'm extremely pleased to receive all these honors, which reflect the groundbreaking research and projects I've had the opportunity to work on with my colleagues at Caltech, JPL and NASA through the years," Elachi said.

This week, Elachi accepted the 2011 General James E. Hill Lifetime Space Achievement Award from the Space Foundation. The award was presented at the National Space Symposium in Colorado Springs, Colo.

The award, named for the Space Foundation's former chairman, Gen. James E. Hill, USAF (retired), recognizes "outstanding individuals who have distinguished themselves through lifetime contributions to the welfare or betterment of humankind through exploration, development and use of space, or through use of space technology, information, themes or resources in academic, cultural, industrial or other pursuits of broad benefit to humanity."

On March 5, Elachi was presented with an honorary doctor of science degree by Occidental College in Los Angeles during its 40th annual President's Circle Dinner at JPL. Also in March, he received the American Astronautical Society's 2011 Carl Sagan Memorial Award at the organization's symposium in Greenbelt, Md. The award, presented in cooperation with the Planetary Society, is given to individuals who demonstrate leadership in research or policies advancing exploration of the cosmos.

In addition to the trio of awards he has accepted in the United States this year, Elachi is receiving two international honors.

He is being inducted into the French Legion, known as the Chevalier de la Legion d'Honneur. Although Elachi is a native of Lebanon, and the award is traditionally restricted to natives of France, the honor has been bestowed on foreign nationals "who have served France or the ideals it upholds." Being honored at age 16 as Lebanon's top science student enabled Elachi to attend the college of his choice, France's University of Grenoble, where he earned a bachelor's degree in physics in 1968. That same year, he received an engineering degree from the Polytechnic Institute in Grenoble, where he graduated first in the class.

"I'm very honored to be recognized with such a prestigious award," said Elachi, who will formally accept the honor for his life's work at a ceremony in the near future. "The years I spent in France, at the University of Grenoble and the Polytechnic Institute in Grenoble, were an important part of my life and helped pave the way for my career."

After studying in France, Elachi moved to Pasadena, where he received a master's (1969) and Ph.D. (1971) in electrical sciences from the California Institute of Technology. He also earned a master's degree (1983) in geology from UCLA and an MBA (1979) from USC.

Elachi noted that throughout his career, his links to France have continued through his research.

He joined JPL in 1970 as a researcher on various Earth and planetary missions. Elachi has been serving as JPL director since May 2001, and the decade since then has included such successful NASA space missions as the Mars Exploration Rovers Spirit and Opportunity, the Phoenix Mars Lander, Stardust, Spitzer, Kepler, and such Earth-orbiting satellites as Grace and Topex/Poseidon-Jason.

"Over the last three decades, JPL and the French Space Agency, working together, have revolutionized the field of oceanography by developing the capability to observe and monitor ocean currents on a global basis from space," Elachi said.

In addition to serving as JPL director, Elachi is vice president of Caltech, and an electrical engineering and planetary science professor. Caltech manages JPL for NASA.

Elachi has recently been listed in the top 10 on the Arabian Business Magazine "Power 500" list of the world's most influential people of Arab descent. The award looks at the influence of people from the Middle East in every sector: from the business world, media, entertainment, sports, science, arts and academia. Elachi is described as "one person who has driven mankind's thirst for knowledge about the other planets in our solar system."

For more information visit http://www.nasa.gov/topics/people/features/elachi20110419.html

"The formation of the clouds requires both water and incredibly low temperatures," says Charles Jackman, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., who is NASA's project scientist for AIM. "The temperatures turn out to be one of the prime driving factors for when the clouds appear."

So the appearance of the noctilucent clouds, also known as polar mesospheric clouds or PMCs since they occur in a layer of the atmosphere called the mesosphere, can provide information about the temperature and other characteristics of the atmosphere. This in turn, helps researchers understand more about Earth's low altitude weather systems, and they've discovered that events in one hemisphere can have a sizable effect in another.

Since these mysterious clouds were first spotted, researchers have learned much about them. They light up because they're so high that they reflect sunlight from over the horizon. They are formed of ice water crystals most likely created on meteoric dust. And they are exclusively a summertime phenomenon.

"The question people usually ask is why do clouds which require such cold temperatures form in the summer?" says James Russell, an atmospheric scientist at Hampton University in Hampton, Va., who is the Principal Investigator for AIM. "It's because of the dynamics of the atmosphere. You actually get the coldest temperatures of the year near the poles in summer at that height in the mesosphere."

As summer warmth heats up air near the ground, the air rises. As it rises, it also expands since atmospheric pressure decreases with height. Scientists have long known that such expansion cools things down – just think of how the spray out of an aerosol can feels cold – and this, coupled with dynamics in the atmosphere that drives the cold air even higher, brings temperatures in the mesosphere down past a freezing -210º F (-134 ºC).

In the Northern hemisphere, the mesosphere reaches these temperatures consistently by the middle of May. Since AIM has been collecting data, the onset of the Northern season has never varied by more than a week or so. But the southern hemisphere turns out to be highly variable. Indeed, the 2010 season started nearly a month later than the 2009 season.

Atmospheric scientist Bodil Karlsson, a member of the AIM team, has been analyzing why the start of the southern noctilucent cloud season can vary so dramatically. Karlsson is a researcher at Stockholm University in Sweden, though until recently she worked as a post-doctoral researcher at the University of Colorado. A change in when some pretty clouds show up may not seem like much all by itself, but it's a tool for mapping the goings-on in the atmosphere, says Karlsson.

"Since the clouds are so sensitive to the atmospheric temperatures," says Karlsson. "They can act as a proxy for information about the wind circulation that causes these temperatures. They can tell us that the circulation exists first of all, and tell us something about the strength of the circulation."

She says the onset of the clouds is timed to something called the southern stratospheric vortex – a winter wind pattern that circles above the pole. In 2010, that vortex lingered well into the southern summer season, keeping the lower air cold and interfering with cloud formation. This part of the equation is fairly straightforward and Karlsson has recently submitted a paper on the subject to the Journal of Geophysical Research. But this is not yet the complete answer to what drives the appearance of these brightly lit clouds.

AIM researchers also believe there is a connection between seemingly disparate atmospheric patterns in the north and south. The upwelling of polar air each summer that contributes to noctilucent cloud formation is part of a larger circulation loop that travels between the two poles. So wind activity some 13,000 miles (20,920 km) away in the northern hemisphere appears to be influencing the southern circulation.

The first hints that wind in the north and south poles were coupled came in 2002 and 2003 when researchers noticed that despite a very calm lower weather system near the southern poles in the summer, the higher altitudes showed variability. Something else must be driving that change.

Now, AIM's detailed images of the clouds have enabled researchers to look at even day-to-day variability. They've spotted a 3 to10 day time lag between low-lying weather events in the north – an area that, since it is fairly mountainous, is prone to more complex wind patterns – and weather events in the mesosphere in the south. On the flip side, the lower atmosphere at the southern poles has little variability, and so the upper atmosphere where the clouds form at the northern poles stays fairly constant. Thus, there's a consistent start to the cloud season each year.

"The real importance of all of that," says Hampton's Russell, "is not only that events down where we live can affect the clouds 50 miles (80 km) above, but that the total atmosphere from one pole to the next is rather tightly connected."

Hammering out the exact mechanisms of that connection will, of course, take more analysis. The noctilucent cloud season will also surely be affected by the change in heat output from the sun during the upcoming solar maximum. Researchers hope to use the clouds to understand how the sun's cycle affects the Earth's atmosphere and the interaction between natural- and humankind-caused changes.

"These are the highest clouds in Earth's atmosphere, formed in the coldest place in Earth's atmosphere," says Goddard's Jackman. "Although the clouds occur only in the polar summer, they help us to understand more about the whole globe."

AIM is a NASA-funded Small Explorers (SMEX) mission. NASA Goddard manages the program for the agency's Science Mission Directorate at NASA headquarters in Washington. The mission is led by the Principal Investigator from the Center for Atmospheric Sciences at Hampton University in Virginia. The Laboratory for Atmospheric and Space Physics (LASP), University of Colorado, Boulder, and the Space Dynamics Laboratory, Utah State University, built the instruments. LASP also manages the mission and controls the satellite.

For more information visit http://www.nasa.gov/mission_pages/aim/news/notilucent-change.html

"The Primary mirror EDU will be used next year to check out optical test equipment developed by Goddard and slated to be used to test the full Flight Primary mirror," said Lee Feinberg, the Optical Telescope Element Manager for the Webb telescope at NASA Goddard. "Following that, the primary and secondary EDU's will actually be assembled onto the Pathfinder telescope. The Pathfinder telescope includes two primary mirror segments (one being the Primary EDU) and the Secondary EDU and allows us to check out all of the assembly and test procedures (that occur both at Goddard and testing at Johnson Space Center, Houston, Texas) well in advance of the flight telescope assembly and test."

The primary mirror is actually composed of 18 smaller hexagonal mirrors that are assembled together into what appears to be a giant hexagon that sits atop the Webb telescope's sunshield. Webb Telescope's scientists and engineers determined that a primary mirror measuring 6.5 meters (21 feet 4 inches) across is what was needed to measure the light from these distant galaxies. Each of these mirrors is constructed from beryllium, a light and strong metal. Each of the 18 mirror segments weighs approximately 20 kilograms (46 pounds).

Why are the mirrors hexagonal shaped? Because a hexagon allows a segmented mirror to fit together without gaps. When Webb's primary mirror is focused on a distant star for example, that image will appear in all 18 mirror segments. To focus on the star and get one image, the mirror segments can then be tilted to align the 18 separate images into a single image.

Although there are 18 segments, there are three different optical prescriptions for the 18 segments: six segments of each prescription. The segment received is the first of the "A" prescription segments for which a total of 7 will be made - 6 flight and 1 spare. A prescription is similar to an eyeglass prescription and specifies a unique mirror curvature. Like eyeglasses, mirrors with the same prescription are interchangeable.

The primary mirror EDU that arrived at Goddard is also a flight spare. That means it can be used on the actual telescope. In fact, it could even be put on the telescope now if needed.

The primary mirror segment has already been cleaned and coated. Ball Aerospace & Technologies cleaned the mirror segment and Quantum Coating, Inc., in Moorestown, N.J., coated it. Ball Aerospace then took the mirror segment back, reassembled it with mounts and actuators and conducted final vibration testing.

Afterward, the mirror segment went back to the X-ray and Cryogenic Facility (XRCF) in Huntsville, Ala., where Ball performed final cryogenic acceptance testing on the segment before it came to NASA Goddard.

The secondary mirror on the Webb telescope will direct the light from the primary mirror to where it can be collected by the Webb's instruments. The secondary mirror is connected to "arms" that position it in front of the 18 primary mirror segments. It will focus all of the light from the 18 primary mirrors.

The secondary EDU at Goddard is not coated but can be, so it can be a flight spare once coated.

Eventually, the final flight mirrors will all come to NASA Goddard and be assembled on the telescope and the instrument module. Then, as a complete unit it will undergo acoustic and vibration testing at Goddard.

The James Webb Space Telescope is the world’s next-generation space observatory and successor to the Hubble Space Telescope. The most powerful space telescope ever built, Webb will observe the most distant objects in the universe, provide images of the very first galaxies ever formed and see unexplored planets around distant stars. The Webb Telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.

For more information visit http://www.nasa.gov/topics/technology/features/two-webb-mirrors.html