Just in time for the holidays: a Hubble Space Telescope picture postcard of hundreds of brilliant blue stars wreathed by warm, glowing clouds. The festive portrait is the most detailed view of the largest stellar nursery in our local galactic neighborhood.

The massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way. There is no known star-forming region in our galaxy as large or as prolific as 30 Doradus.

Many of the diamond-like icy blue stars are among the most massive stars known. Several of them are over 100 times more massive than our Sun. These hefty stars are destined to pop off, like a string of firecrackers, as supernovas in a few million years.

The image, taken in ultraviolet, visible, and red light by Hubble's Wide Field Camera 3, spans about 100 light-years. The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the stars' birth and evolution.

The brilliant stars are carving deep cavities in the surrounding material by unleashing a torrent of ultraviolet light, and hurricane-force stellar winds (streams of charged particles), which are etching away the enveloping hydrogen gas cloud in which the stars were born. The image reveals a fantasy landscape of pillars, ridges, and valleys, as well as a dark region in the center that roughly looks like the outline of a holiday tree. Besides sculpting the gaseous terrain, the brilliant stars can also help create a successive generation of offspring. When the winds hit dense walls of gas, they create shocks, which may be generating a new wave of star birth.

The movement of the LMC around the Milky Way may have triggered the massive cluster's formation in several ways. The gravitational tug of the Milky Way and the companion Small Magellanic Cloud may have compressed gas in the LMC. Also, the pressure resulting from the LMC plowing through the Milky Way's halo may have compressed gas in the satellite. The cluster is a rare, nearby example of the many super star clusters that formed in the distant, early universe, when star birth and galaxy interactions were more frequent. Previous Hubble observations have shown astronomers that super star clusters in faraway galaxies are ubiquitous.

The LMC is located 170,000 light-years away and is a member of the Local Group of Galaxies, which also includes the Milky Way.

The Hubble observations were taken Oct. 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen.

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 conducts Hubble science operations. The institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, and is an International Year of Astronomy 2009 program partner.

Images and more information are available at:

› HubbleSite

This Global Digital Elevation Model, or GDEM, is a product of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), a joint program of NASA and Japan's Ministry of Economy, Trade and Industry. The image was released on June 29, 2009, and was created by processing and stereo-correlating the 1.3 million-scene ASTER archive of optical images, covering Earth's land surface between 83 degrees North and 83 degrees South latitudes. The GDEM is produced with 98-feet postings, and is formatted as 23,000 one-by-one-degree tiles. In this colorized version, low elevations are purple, medium elevations are greens and yellows, and high elevations are orange, red and white.

With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 50 to 300 feet, ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on NASA's Terra satellite.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping and monitoring of dynamic conditions and temporal change.

Scientists at NASA’s Langley Research Center have completed a first attempt to accurately calculate the level of damaging radiation flight crews and passengers are exposed to on commercial airline flights. The work is an early step toward developing a model to observe radiation exposure for all commercial flights, particularly for pilots and crews who spend their careers airborne and who are at greater risk of developing certain cancers.

The study considered not only everyday radiation emanating from space, but also the additional energy unleashed during a solar storm, which can be profound. NASA scientists say not including geomagnetic effects on solar radiation in modeling radiation exposure could underestimate the dosage by 30 to 300 percent.

Researchers looked at passengers and crew on typical flights from Chicago to Beijing, Chicago to Stockholm and London to New York, during what is known as the Halloween 2003 Storm. These flights were chosen because of their long flight paths near the North Pole, where the Earth’s natural protection from radiation is weakest. Earth’s magnetic field approaches zero above the poles. The Halloween 2003 event was chosen because it was both a large and a complex storm, making it a good test for the model.

The study found that aircrew and passengers during the Chicago to Beijing flight, for example, would have been exposed to about 12 percent of the annual radiation limit recommended by the International Committee on Radiological Protection. But these exposures were greater than on typical flights at lower latitudes, and confirmed the concerns about commercial flights at high latitudes.

“The upshot is that these international flights were right there at that boundary where many of these events can take place, where radiation exposure can be much higher,” said Chris Mertens, senior research scientist at NASA’s Langley Research Center, who is leading the research effort. Mertens will present his latest results at the American Geophysical Union fall meeting in San Francisco on Dec. 16.

Piecing together the radiation exposure on these typical flights is the first step toward developing a real-time system that researchers hope will become a standard component of commercial airline cockpits. Radiation exposure could one day be taken into account in the same way weather conditions are considered before deciding to fly or deciding what exact route to fly and at what altitude.

Flying above and beyond Earth’s natural protection

The number of international flights that skirt the north pole are increasing. Airlines save massive amounts of fuel on flights such as Chicago-to-Shanghai by simply flying “over the top” – it is a far shorter route than following the latitude lines. But while saving fuel, these flight paths take planes and their passengers to the thinner layers of Earth’s magnetosphere, which shields potentially harmful solar and cosmic radiation.

On a typical day, the Sun is quiet and “background radiation,” the cumulative effect of radiation from cosmic sources reaching Earth, is the only other source. But when the Sun is not quiet, violent storms on the star’s surface eject powerful bursts of radiation to the Earth. It is these events that have never been truly accounted for in studies of how much radiation pilots and airline passengers are exposed to.

Pilots Await Results

While the flights studied appear to have not put passengers in danger of exceeding the safe radiation limit in an individual flight, concerns remain, Mertens said. Many workers whose jobs expose them to consistent radiation sources log that exposure to keep a record over one’s career. People who work on commercial airline flights are technically listed as “radiation workers” by the federal government – a classification that includes nuclear plant workers and X-ray technicians. But unlike some others in that category, flight crews do not quantify the radiation they are exposed to.

Mike Holland, an American Airlines captain and vice chairman for radiation and environmental issues with the Allied Pilots Association, said he is following Mertens’ research with interest. The pilots association has written a formal letter in support of the research. Holland cited studies that show pilots face a four-times greater risk of melanoma than the general population. But because pilots and flight crews do not wear radiation-measuring badges like other radiation workers, the only estimates about their career-long exposure come from models.

Up until now, most of those models only attempted to capture the amount of cosmic background radiation that reaches airliners in flight. Holland said he believes including solar radiation, especially during solar storms, is important. He looks forward to having answers for the pilots who contact him with questions about radiation and cancer risk.

“When I talk to epidemiologists, they have two questions for me: What is your exposure? And what is your health for 20 to 30 years after you retire?” Holland said. The second question he and other pilots can answer, in time. But as of now, they can’t measure their exposure.

“We’re excited that Chris is doing this,” Holland said, “and we hope it can answer the epidemiologists first question, which is, ‘What is your exposure?’”

Related Links:

> NAIRAS at Space Environment Technologies
> Advanced Satellite Aviation Weather Products (ASAP)
> NASA's Applied Sciences Program

Diagnostic tests were run on Spirit's right-rear wheel and right-front wheel on Sol 2013 (Dec. 12, 2009). The right-rear wheel, which stalled during a drive two weeks earlier, continued to show no motion in the latest tests and exhibited very high resistance in the motor winding. The right-front wheel, which stopped operating on Sol 779 (March 13, 2006), surprised engineers by indicating normal resistance and turning slightly during a resistance test for that wheel.

Researchers studying carbon dioxide, a leading greenhouse gas and a key driver of global climate change, now have a new tool at their disposal: daily global measurements of carbon dioxide in a key part of our atmosphere. The data are courtesy of the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua spacecraft.

> See all images and animations

Variations in composition of light-toned deposits in troughs on Mars suggest a diversity of water-related processes, based on analysis of observations by NASA's Mars Reconnaissance Orbiter.

› Read the Planetary Science Institute release

December 18, 2009, marks the tenth year since the launch of Terra, one of NASA's "flagship" Earth observing satellites. But the decade is more than just a mechanical milestone. With each additional day and year that the satellite monitors Earth, scientists achieve a lengthened record of Earth's vital signs. It's that record that helps scientists assess the health of Earth's ocean, land, and atmosphere, and determine how these systems are changing.

"Earth system science is a relatively young science," said Marc Imhoff, project scientist for the mission and a researcher at NASA's Goddard Space Flight Center in Greenbelt, Md. "Terra's sensors have provided the first coordinated set of observations allowing us to link Earth system processes across space and time so we can better understand how they function together and how we interact with them."

Since Terra's five instruments officially saw "first light" on Feb 24, 2000, after a post-launch checkout, the data have continued to advance Earth system science. Here's a sample of the latest developments to be presented by Terra researchers at the Fall Meeting of the American Geophysical Union in San Francisco.

Droughts Slow Earth's Carbon Metabolism

Data from Terra's Moderate Resolution Imaging Spectroradiometer (MODIS) have turned up evidence that climate change may have negative effects for ecosystems earlier than we thought, according to Maosheng Zhao, an ecologist at the University of Montana in Missoula.

For the past several decades, photosynthesis by land plants and trees has absorbed, or acted as a "sink," for about one third of global carbon dioxide emissions, helping to slow the increase of the greenhouse gas in the atmosphere. But scientists have found that global carbon uptake by land plants is declining.

"This decreasing trend has very important implications for how much and how long humans should count on the carbon sink capacity of terrestrial ecosystems," Zhao said.

To arrive at their finding, Zhao and colleagues analyzed MODIS data from 2000 to 2008. Directly measuring carbon dioxide from space is difficult, so scientists rely on sensors to measure the photosynthetic activity of plants. That activity can then be translated to an estimate of how much carbon dioxide the plants are absorbing. "So far, MODIS is the best sensor we have for monitoring global vegetation dynamics," Zhao said.

A closer look reveals that carbon uptake is still on the rise in middle and high latitudes of the northern hemisphere. But that benefit is outweighed by changes in the tropics and southern hemisphere, where scientists observed less carbon being absorbed.

Zhao thinks that a major cause of the decrease is warming-related droughts, which impact crop yields, timber production, and expanses of natural vegetation.

Some computer models have predicted that by the middle of this century, carbon-climate feedbacks could cause terrestrial ecosystems to shift from being carbon sinks to sources, according to Zhao. "Our result is an early warning that we must take some actions to mitigate human-induced climate change."

Natural Hazards Tracked

There's no escaping the risk to human populations posed by natural hazards. But for almost 10 years, Terra has helped governments and local groups respond to and mitigate the consequences.

Just last month in El Salvador, Hurricane Ida brought heavy rains that triggered flooding and deadly mudslides. In another incident in November, a major algal bloom in Guatemala's Lake Atitlan had residents concerned about the lake's health and the safety of people who swim in and drink the water.

To help monitor these hazards, local governments and data processing groups turn to NASA for images from Terra's Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER ). The instrument's spatial resolutions of about 15 to 90 meters produce detailed maps of land surface characteristics such as temperature, reflectance and elevation, which are key for helping decision-makers determine where and how to respond.

"The request for the mudslide and algal bloom images are typical of the types of requests we receive," said Michael Abrams, ASTER science team leader at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We also work with the U.S. Forest Service to image active wildfires for logistical support and often for post-fire damage assessment and mitigation."

Instrument operators can point ASTER -- an instrument provided by Japan's Ministry of Economy Trade and Industry -- at specific targets and acquire about 500 images per day. Each day about 3,000 requests are active in the request database, ranging from field work, global maps, and regional monitoring. To decide where to point the instrument, an algorithm was developed to automatically prioritize requests.

For example, immediate threats such as the requests from El Salvador's Civil Protection Agency to monitor the flooding and mudslides and Guatemala's Ministry of Agriculture to monitor the algal bloom, receive higher priority. Lower priority targets include a project to obtain complete global maps of ASTER imagery at least 3-5 times during mission.

As part of its monitoring of natural hazards, ASTER has been keeping a long-term eye on more than 1,000 active volcanoes around the world. The extended archive will be used by researchers to characterize the historical behavior for each volcano.

"To improve prediction, we need to know which signals are important," Abrams said.

Pollution Travels High and Far

The Station wildfire that burned southern California in late August 2009 was the largest fire in the recorded history of Los Angeles County and its Angeles National Forest, with more than 160,577 acres burned. Pollution created by the wildfire traveled even further. Rising more than 4 miles (7 kilometers) above Earth's surface, smoke from the fire was carried over Nevada, Utah, and Colorado, and carbon monoxide from the fire traveled at least as far as Louisiana.

The measurement of smoke height was possible with Terra's Multiangle Imaging SpectroRadiometer (MISR ), which can resolve atmospheric components -- such as, clouds, dust and smoke plumes -- in three dimensions. MISR can also measure horizontal winds.

Scientists have used the instrument to develop a multi-year "climatology" or statistical database of the heights to which wildfires inject smoke into the atmosphere. The database now contains observations from more than 7,000 smoke plumes in North America, Siberia, and Africa.

"We discovered that for about one-fifth of wildfires, the smoke particles escape the low, turbulent part of the atmosphere and rise to a higher altitude, where they can remain concentrated for long periods and also be transported great distances " said David Diner, MISR principal investigator at JPL.

Researchers studying the dispersal of particulates from wildfires, volcanoes, and dust storms also use the data to test theoretical simulations against observed behavior. These simulations will help researchers understand, for example, what the effect of more fires in a warmer climate might have on air quality.

Other scientists are watching pollution that travels even greater distances, across international boundaries. Measurements of carbon monoxide from the Measurements of Pollution in the Troposphere instrument MOPITT -- provided by the Canadian Space Agency -- and of aerosols from the MISR and MODIS instruments allow scientists to observe both the sources and transport of pollution on a global scale.

"The Terra satellite made it possible to track pollution plumes as they are transported across the ocean, allowing us to observe numerous plumes of Asian pollution transported to the United States," said Daniel Jacob, an atmospheric scientist at Harvard University in Cambridge, Mass. "The findings show that air pollution is a global issue, and thus that meeting air quality goals in the United States will increasingly require international cooperation."

Balancing the Energy Budget

As society considers carbon dioxide caps and geoengineering, open questions remain about exactly how, why, and where Earth is warming. Answering those questions requires a clear picture of how the Earth's energy budget is changing.

For a decade, researchers using the Clouds and the Earth's Radiant Energy System (CERES) experiment on Terra have been taking stock of how much solar energy is absorbed by the planet's atmosphere and surface, and how much infrared and heat energy is emitted back into space. CERES scientists also study how cloud properties influence the energy exchange from space to the atmosphere to the ground and back again.

"CERES has provided a decade of accurate observations that allow us to explore changes over time, to see how radiation at the top of the atmosphere varies seasonally and annually," said Kevin Trenberth, A CERES investigator from the National Center for Atmospheric Research in Boulder, Colo. "The longer the record, the more valuable it becomes."

The observations have shown that the world is cloudier than we thought, and changes in cloudiness can lead to regional and global fluctuations in the heat budget. For instance, albedo is decreasing in the Arctic as snow and sea ice melt, but there is also evidence of compensation from an increase in cloud cover.

Researchers including Norman Loeb of NASA's Langley Research Center, Hampton, Va., and principal investigator for the CERES instrument, have found that measurements of the energy budget from space correlate well with what is being observed by heat content observations in the ocean, where most solar heat retained by Earth is stored.

Most strikingly, the CERES science team has updated the numbers in the planetary budget ledger and found a gap between incoming and outgoing radiation. The Earth is estimated to be absorbing at a rate of about 0.9 Watts per square meter more than it is emitting -- large enough to provoke the question: what does it mean for climate change?

"Terra has allowed us to observe cloud heights with MISR; cloud density and coverage, with MODIS, as well as sea ice, glaciers and surface temperatures; and incoming and outgoing radiation with CERES," said Marc Imhoff, project scientist for Terra. "That's a very powerful combo for understanding how the atmosphere, land, and oceans work together in balancing heat."

Related AGU talks
Wednesday, Dec. 16
U31C-01 Tracking Earth's global energy
U31C-05 Terra at 10: CERES Results
U32A-01 Geological mapping and hazards monitoring using ASTER data
U32A-02 Using Terra observations to quantify sources and intercontinental transport of pollution
U32A-04 MISR at 10: Looking back, ahead, and in between
U32A-07 Variations and trends of terrestrial primary production observed by MODIS

Related links:

NASA's American Geophysical Union homepage
› http://www.nasa.gov/topics/earth/agu/index.html
Related story: Terra details urban heat islands
› http://www.nasa.gov/mission_pages/terra/news/heat-islands.html

Terra Tracks Ten Years of Change
› terra.nasa.gov/Ten
Terra: The EOS Flagship
› terra.nasa.gov

About Terra
› earthobservatory.nasa.gov/Features/AM1

World of Change
› earthobservatory.nasa.gov/Features/WorldOfChange

Landslides in El Salvador
› earthobservatory.nasa.gov/NaturalHazards/view.php?id=41365

Drought Cycles in Australia
› earthobservatory.nasa.gov/Features/WorldOfChange/australia.php
Tracking Nature's Contribution to Pollution
› earthobservatory.nasa.gov/Features/ContributionPollution
Climate and Earth's Energy Budget
› earthobservatory.nasa.gov/Features/EnergyBalance

Seasonal Changes in Global Net Radiation
› earthobservatory.nasa.gov/IOTD/view.php?id=35555

Earth's Energy Budget Animations
› svs.gsfc.nasa.gov/vis/a010000/a010300/a010395/index.html

NASA and the Kingdom of Saudi Arabia's King Abdulaziz City for Science and Technology (KACST) have signed a joint statement that allows for collaboration in lunar and asteroid science research. The partnership recognizes the Saudi Lunar and Near-Earth Object Science Center as an affiliate partner with the NASA Lunar Science Institute at NASA's Ames Research Center in Moffett Field, Calif.

"This collaboration is within the scope of the Memorandum of Understanding on Science and Technology signed between the Kingdom of Saudi Arabia and the United States of America last year and later ratified by the Council of Ministers," said H.H. Dr. Turki Bin Saud Bin Mohammed Al-Saud, vice president for Research Institutes, KACST. "The international interest in lunar science and, more recently, near Earth objects led to the establishment of the Saudi Lunar and Near Earth Object Science Center as a focal point for lunar science and NEO studies in the Kingdom of Saudi Arabia. Furthermore, we are looking forward to our expanding collaboration with NASA for the benefit of both countries."

"NASA's Lunar Science Institute exists to conduct cutting-edge lunar science and train the next generation of lunar scientists and explorers," said Greg Schmidt, institute deputy director at Ames. "Our international partnerships are critical for meeting these objectives, and we are very excited by the important science, training and education that our new Saudi colleagues bring to the NASA Lunar Science Institute."

"This is an important advance in our growing program of bilateral science and technology cooperation," said U.S. Ambassador to Saudi Arabia James Smith. "It will help realize President Obama's goal, expressed in his June 4 speech to the Muslim world, of increasing our cooperation on science and technology, which we believe closely corresponds to King Abdullah's vision."

The Saudi science center's proposal brings technical and engineering expertise to advance the broad goals of lunar science at the institute. Specific areas of lunar study of both scientific and cultural importance include radar and infrared imaging, laser ranging and imaging, and topographical studies. The center's studies in near-Earth object science also offer important contributions to an area of importance to NASA.

"The Saudi Lunar and Near Earth Object Science Center's primary mission is to direct all lunar and near Earth object related research within the Kingdom of Saudi Arabia," said Dr. Haithem Altwaijry, deputy director of the National Satellite Technology Program at KACST. "It will reach out to students in addition to researchers and present fertile ground for scientific research."

"NASA welcomes international cooperation for mutual benefit with organizations large and small in all regions of the world," said Michael O'Brien, assistant administrator for external relations at NASA Headquarters in Washington. "Our continuing discussions with Saudi Arabian officials may lead to future joint scientific collaboration in other areas of mutual interest."

To learn more about the NASA Lunar Science Institute visit:

Astronauts are not the only ones earning wings on the International Space Station. Butterflies emerged aboard the station recently, to the delight of science students across the country. That experiment and studies of bacteria that advance research about food poisoning and infections are the subjects of live NASA TV satellite interview opportunities from 6 a.m. to 8 a.m. CST on Friday, Dec. 18.

International Space Station Program Scientist Julie Robinson will be available for interviews along with Dr. Nancy Moreno, a principal investigator of the Painted Lady butterfly education activities. Moreno is a professor at the Baylor College of Medicine who is conducting the butterfly research with the National Space Biomedical Research Institute in Houston and the University of Colorado at Boulder.

To participate in the interviews, media representatives must contact the newsroom at NASA's Johnson Space Center in Houston at 281-483-5111 by 1 p.m. on Thursday, Dec. 17. B-roll of the butterflies in space and other recent station research will be broadcast beginning at 5:30 a.m.

The butterfly experiment, which included stunning Monarch and Painted Lady butterflies, is focused on stimulating science education across the country by studying the insects' development and behavior in microgravity. Hundreds of science teachers are participating with ground-based versions of the study and sharing the excitement with their students. The Monarchs were the first to be sent into space, while the Painted Ladies were the first to undergo a full metamorphosis from larva to pupa to adult while in orbit.

Other recent experiments on the station are making advances in the fight against food poisoning, testing new methods for delivering medicine to fight cancer cells, and investigating better materials for future spacecraft.

The NASA Live Interview Media Outlet channel will be used for the interviews. The channel is a digital satellite C-band downlink by uplink provider Americom. It is on satellite AMC 6, transponder 5C, located at 72 degrees west, downlink frequency 3785.5 Mhz based on a standard C-band 5150 Mhz L.O., vertical polarity, FEC is 3/4, data rate is 6.00 Mhz, symbol rate is 4.3404 Mbaud, transmission DVB, minimum Eb/N0 is 6.0 dB.

The interviews also will be broadcast live on NASA TV. For streaming video, downlink and scheduling information, visit:

For more information about the International Space Station, visit:

For more about scientific studies aboard the space station, visit:

NASA has purchased two reusable solid rocket motors from ATK Launch Systems Inc. of Brigham City, Utah, to provide a "launch on need" rescue capability for the final planned space shuttle mission, targeted for September 2010.

The reusable solid rocket motors are the propellant-loaded sections of the solid rocket boosters that provide thrust for the first two minutes of a shuttle flight. The $64.6 million modification brings the total value of the contract, which was awarded in October 1998, to $4.1 billion and covers work started in February to produce and transport the two motors.

Work will be performed at the contractor's plants in Brigham City and Clearfield, Utah, and facilities at NASA's Marshall Space Flight Center in Huntsville, Ala., and Kennedy Space Center in Florida.

For more information about the Space Shuttle Program, visit:

Next-generation interactive moon mission simulations, social networking curricula centered on missions to Mars, and engineering design challenges are among 13 education projects NASA has selected for funding. Other funded programs focus on equipping teachers to integrate space and science into their classrooms.

NASA awarded a total of $12.1 million in grants to public school districts, state-based education leadership and not-for-profit education organizations in California, Idaho, Michigan, New Jersey, New York, North Carolina, Oklahoma, Texas and Virginia. Winning proposals were selected through a merit-based, peer-reviewed competition. The awards have a two-year period of performance and range in value from $350,000 to approximately $1.2 million.

The selected proposals leverage NASA's unique contributions in science, technology, engineering and mathematics to enhance secondary students' academic experiences and improve educators' abilities to engage and stimulate their students. The chosen projects demonstrate innovative approaches to using NASA-themed content to improve teaching and learning, with a particular emphasis on high school education.

The cooperative agreements are part of a program Congress began in fiscal year 2008. For a list of selected organizations and projects descriptions, click on "Selected Proposals" and look for "FY 2009 NASA K-12 Cooperative Agreements Notice" or solicitation NNG09Z13001, at:

For information about NASA's education programs, visit:

NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite has captured five complete polar seasons of noctilucent (NLC) or "night-shining" clouds with an unprecedented horizontal resolution of 3 miles by 3 miles. Results show that the cloud season turns on and off like a "geophysical light bulb" and they reveal evidence that high altitude mesospheric "weather" may follow similar patterns as our ever-changing weather near the Earth's surface. These findings were unveiled today at the Fall Meeting of the American Geophysical Union today in San Francisco.

The AIM measurements have provided the first comprehensive global-scale view of the complex life cycle of these clouds, also called Polar Mesospheric Clouds (PMCs), over three entire Northern Hemisphere and two Southern Hemisphere seasons revealing more about their formation, frequency and brightness and why they appear to be occurring at lower latitudes than ever before.

"The AIM findings have altered our previous understanding of why PMCs form and vary," stated AIM principal investigator Dr. James Russell III of Hampton University in Hampton, Va. "We have captured the brightest clouds ever observed and they display large variations in size and structure signifying a great sensitivity to the environment in which the clouds form. The cloud season abruptly turns on and off going from no clouds to near complete coverage in a matter of days with the reverse pattern occurring at the season end."

These bright "night-shining" clouds, which form 50 miles above Earth's surface, are seen by the spacecraft's instruments, starting in late May and lasting until late August in the north and from late November to late February in the south. The AIM satellite reports daily observations of the clouds at all longitudes and over a broad latitude range extending from 60 to 85 degrees in both hemispheres.

The clouds usually form at high latitudes during the summer of each hemisphere. They are made of ice crystals formed when water vapor condenses onto dust particles in the brutal cold of this region, at temperatures around minus 210 to minus 235 degrees Fahrenheit. They are called "night shining" clouds by observers on the ground because their high altitude allows them to continue reflecting sunlight after the sun has set below the horizon. They form a spectacular silvery blue display visible well into the night time.

Sophisticated multidimensional models have also advanced significantly in the last few years and together with AIM and other space and ground-based data have led to important advances in understanding these unusual and provocative clouds. The satellite data has shown that:

1. Temperature appears to control season onset, variability during the season, and season end. Water vapor is surely important but the role it plays in NLC variability is only now becoming more understood,

2. Large scale planetary waves in the Earth's upper atmosphere cause NLCs to vary globally, while shorter scale gravity waves cause the clouds to disappear regionally;

3. There is coupling between the summer and winter hemispheres: when temperature changes in the winter hemisphere, NLCs change correspondingly in the opposite hemisphere.

Computer models that include detailed physics of the clouds and couple the upper atmosphere environment where they occur with the lower regions of the atmosphere are being used to study the reasons the NLCs form and the causes for their variability. These models are able to reproduce many of the features found by AIM. Validation of the results using AIM and other data will help determine the underlying causes of the observed changes in NLCs.

The AIM results were produced by Mr. Larry Gordley and Dr. Mark Hervig and the Solar Occultation for Ice Experiment (SOFIE) team, Gats, Inc., Newport News, Va. and Dr. Cora Randall and the Cloud Imaging and Particle Size (CIPS) experiment team, University of Colorado, Laboratory for Atmospheric and Space Physics in Boulder and Dr. Scott Bailey, Va. Tech, Blacksburg, Va.; Modeling results were developed by Dr. Daniel Marsh of the National Center for Atmospheric Research in Boulder, Colorado and Professor Franz-Josef Lübken of the Leibniz-Institute of Atmospheric Physics, Kühlungsborn, Germany.

AIM is a NASA-funded SMall EXplorers (SMEX) mission. NASA's Goddard Space Flight Center 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 VA. Instruments were built by the Laboratory for Atmospheric and Space Physics (LASP), University of Colorado, Boulder, and the Space Dynamics Laboratory, Utah State University. LASP also manages the AIM mission and controls the satellite. Orbital Sciences Corporation, Dulles, Va., designed, manufactured, and tested the AIM spacecraft, and provided the Pegasus launch vehicle.

For more information about the AIM mission, visit:

http://www.nasa.gov/mission_pages/aim/news/nlc-secrets.html
http://www.nasa.gov/aim
http://aim.hamptonu.edu