FLORIDA -- They came in droves. Hundreds of thousands of spectators expected for Friday's launch of the Endeavour shuttle. A blast-off that was called off just a few hours before its scheduled departure.

"Unfortunately, it happens rather often. The space shuttle is an extraordinarily complicated vehicle," said NASA astronaut Michael Foale.

Problems with the heating system will keep it on the ground, at least for a few days. But that's just part of the story at the Kennedy Space Center. Interest in the lift-off is sky high because of Congresswoman Gabrielle Giffords.

"She has been here today. And I have seen her. She is doing well," Foale said.

Giffords was shot in the head at a meet-and-greet in Tuscon, Arizona back in January. She has a long recovery ahead of her, but with her doctors' blessings, she decided to make the trip. Her husband, Mark Kelly, is the shuttle commander.

"She is where she should be. And if she wasn't here it would be a shame," Foale said.

A reporter who has covered 97 shuttle launches says this one is different and not just because of Giffords.

"It's just a confluence of events. You've got the Mark Kelly-Gabrielle Giffords story. You've got the President coming. The next-to-last shuttle flight, last launch of Endeavour. Just big story, lots of drama, no matter where you turn," said Marcia Dunn of the Associated Press.

President Obama still came here Friday, even though the launch was scrubbed. He met privately with Giffords. The public hasn't seen any sign of her, other than a grainy footage of her boarding a plane to come to Florida. But she is certainly on the minds of many people here.

"I think it's a great thing that the woman has made such a great recovery, to be able to be here with her husband," one person said.

"I think it's incredible that she's able to," another person said.

An incredible journey indeed for Giffords and one that may still include another chapter: The chance to watch her husband go into space one more time.

 

Deadly tornadoes raked across Alabama on April 27, 2011, killing as many as 210 people as of April 29. The hardest-hit community was Tuscaloosa. In an image acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite on April 28, three tornado tracks are visible through and around the city.

The tracks are pale brown trails where green trees and plants have been uprooted, leaving disturbed ground. Though faint, the center track runs from southwest of Tuscaloosa, through the gray city, and extends northeast towards Birmingham. Two other tracks run parallel to the center track. The northernmost track is in an area where the National Weather Service reported a tornado, but no tornado was reported in the vicinity of the more visible southern track. In the southern region, strong winds were reported.

The tornadoes were part of a larger weather pattern that produced more than 150 tornadoes across six states, said the National Weather Service. The death toll had nearly reached 300 on April 29, making the outbreak the deadliest in the United States since 1974.

 

This artist's concept shows NASA's two Voyager spacecraft exploring a turbulent region of space known as the heliosheath, the outer shell of the bubble of charged particles around our sun. Image credit: NASA/JPL-Caltech

NASA will hold a special NASA Science Update at 10 a.m. PDT (1 p.m. EDT) on Thursday, April 28, to discuss the unprecedented journey of NASA's twin Voyager spacecraft to the edge of our solar system.

The event will be held at NASA Headquarters in Washington and will be broadcast live on NASA Television

After 33 years in space, the spacecraft are still operating and returning data from about 16 billion kilometers (10 billion miles) away from our sun. The Voyagers also carry a collection of images and sounds from Earth as a message to possible life elsewhere in the galaxy.

The participants are:
-- Ed Stone, Voyager project scientist and professor of physics, California Institute of Technology, Pasadena, Calif.
-- Ann Druyan, creative director, Voyager Interstellar Message Project; Carl Sagan's co-author and widow
-- Suzanne Dodd, Voyager project manager, NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
-- Merav Opher, Voyager guest investigator and assistant professor of astronomy, Boston University

For more information about the Voyager mission, visit: http://www.nasa.gov/voyager .

For NASA TV streaming video and downlink information, visit: http://www.nasa.gov/ntv .

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jia-rui.c.cook@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.cbrown@nasa.gov

Late last year, astronomers noticed an asteroid named Scheila had unexpectedly brightened, and it was sporting short-lived plumes. Data from NASA's Swift satellite and Hubble Space Telescope showed these changes likely occurred after Scheila was struck by a much smaller asteroid.

Collisions between asteroids create rock fragments, from fine dust to huge boulders, that impact planets and their moons," said Dennis Bodewits, an astronomer at the University of Maryland in College Park and lead author of the Swift study. "Yet this is the first time we've been able to catch one just weeks after the smash-up, long before the evidence fades away."

Asteroids are rocky fragments thought to be debris from the formation and evolution of the solar system approximately 4.6 billion years ago. Millions of them orbit the sun between Mars and Jupiter in the main asteroid belt. Scheila is approximately 70 miles across and orbits the sun every five years.

"The Hubble data are most simply explained by the impact, at 11,000 mph, of a previously unknown asteroid about 100 feet in diameter," said Hubble team leader David Jewitt at the University of California in Los Angeles. Hubble did not see any discrete collision fragments, unlike its 2009 observations of P/2010 A2, the first identified asteroid collision.

The studies will appear in the May 20 edition of The Astrophysical Journal Letters and are available online.

Astronomers have known for decades that comets contain icy material that erupts when warmed by the sun. They regarded asteroids as inactive rocks whose destinies, surfaces, shapes and sizes were determined by mutual impacts. However, this simple picture has grown more complex over the past few years.

During certain parts of their orbits, some objects, once categorized as asteroids, clearly develop comet-like features that can last for many months. Others display much shorter outbursts. Icy materials may be occasionally exposed, either by internal geological processes or by an external one, such as an impact.

On Dec. 11, 2010, images from the University of Arizona's Catalina Sky Survey, a project of NASA's Near Earth Object Observations Program, revealed Scheila to be twice as bright as expected and immersed in a faint comet-like glow. Looking through the survey's archived images, astronomers inferred the outburst began between Nov. 11 and Dec. 3.

Three days after the outburst was announced, Swift's Ultraviolet/Optical Telescope (UVOT) captured multiple images and a spectrum of the asteroid. Ultraviolet sunlight breaks up the gas molecules surrounding comets; water, for example, is transformed into hydroxyl and hydrogen. But none of the emissions most commonly identified in comets, such as hydroxyl or cyanogen, show up in the UVOT spectrum. The absence of gas around Scheila led the Swift team to reject scenarios where exposed ice accounted for the activity.

Images show the asteroid was flanked in the north by a bright dust plume and in the south by a fainter one. The dual plumes formed as small dust particles excavated by the impact were pushed away from the asteroid by sunlight. Hubble observed the asteroid's fading dust cloud on Dec. 27, 2010, and Jan. 4, 2011.`

The two teams found the observations were best explained by a collision with a small asteroid impacting Scheila's surface at an angle of less than 30 degrees, leaving a crater 1,000 feet across. Laboratory experiments show a more direct strike probably wouldn't have produced two distinct dust plumes. The researchers estimated the crash ejected more than 660,000 tons of dust -- equivalent to nearly twice the mass of the Empire State Building.

"The dust cloud around Scheila could be 10,000 times as massive as the one ejected from comet 9P/Tempel 1 during NASA's UMD-led Deep Impact mission," said co-author Michael Kelley, also at the University of Maryland. "Collisions allow us to peek inside comets and asteroids. Ejecta kicked up by Deep Impact contained lots of ice, and the absence of ice in Scheila's interior shows that it's entirely unlike comets."

NASA's Goddard Space Flight Center in Greenbelt, Md., manages Hubble and Swift. Hubble was built and is operated in partnership with the European Space Agency. Science operations for both missions include contributions from many national and international partners.

For more information, video and images associated with this release, visit:
http://svs.gsfc.nasa.gov/goto?10747

 

The F-16D test aircraft takes off from Edwards Air Force Base during the Automatic Collision Avoidance Technology flight test project in June 2009. (NASA photo/Tom Tschida) The U.S. Air Force Research Laboratory's Automatic Collision Avoidance Technology Fighter Risk Reduction Program (ACAT/FRRP) team, which includes NASA's Dryden Flight Research Center, has won an Aviation Week & Space Technology magazine Laureate Award for its successful development and flight test of an Automatic Ground Collision Avoidance System.

The award was announced March 8 during the magazine's 54th Annual Laureate Awards ceremony in Washington, DC.

NASA Dryden led the project's integrated test team, which was responsible for the technical content of the project's test and evaluation, maintenance of the Air Force's F-16D test aircraft, project management and engineering services, and provision of the project's chief pilot.

"It is a tremendous honor to be recognized by Aviation Week this way," said Dryden's Mark Skoog, the team's project manager. "Speaking for the NASA and Air Force Flight Test Center team, we were proud to contribute to this team effort by ironing out the system requirements with Air Combat Command, bringing improved digital data to the system, acquiring and preparing the test jet, as well as conducting and evaluating the thrilling flight test effort," Skoog said.

The Automatic Ground Collision Avoidance System, or Auto GCAS, is a lifesaving aircraft technology that incorporates onboard digital terrain mapping data, a robust terrain scan pattern, and "time to avoid impact" algorithms to predict impending ground collisions and, at the last moment, execute avoidance maneuvers. The result is a system that automatically prevents controlled flight into terrain, the leading cause of all fighter aircraft mishaps.

The U.S. Air Force's F-16D Automatic Collision Avoidance Technology (ACAT) aircraft banks over NASA's Dryden Flight Research Center during a flight in March 2009. (NASA Photo / Jim Ross) By flight-testing the Auto GCAS system across the entire F-16 flight envelope and in all terrain conditions, including such extremes as flying only 100 feet above ground level in canyons and over mountainous terrain, the ACAT/FRRP team successfully proved the maturity of this technology, its ability to be nuisance-free and ready for transition to operational fighter aircraft.

As a direct result of the ACAT/FRRP team efforts and success, Auto GCAS is now transitioning to operational use in the Air Force's F-16 and F-22 aircraft, as well as in the F-35 Joint Strike Fighter.

Auto GCAS offers unprecedented payoffs in terms of operator safety and aircraft retention, according to Air Force Research Laboratory officials. They believe the 20-year projected payoff from implementation of Auto GCAS will result in savings of tens of billions of dollars and hundreds of lives and fighter aircraft.

The ACAT/FRRP team is composed of AFRL, Lockheed Martin, NASA's Dryden Flight Research Center, the Air Force Flight Test Center, and the Office of the Secretary of Defense Personnel and Readiness.

› ACAT Video The annual Aviation Week Laureate Awards recognize extraordinary individuals and teams for their exploration, innovation and vision in the aerospace and defense industry.

he Tropical Rainfall Measuring Mission or TRMM satellite again flew over severe thunderstorms that were spawning tornadoes over the eastern United States on April 28 and detected massive thunderstorms and very heavy rainfall.

TRMM, a satellite managed by both NASA and the Japanese Space Agency, captured the rainfall rates occurring in the line of thunderstorms associated with a powerful cold front moving through the eastern U.S. on April 28. TRMM flew over the strong cold front and captured data at 0652 UTC (2:52 AM EDT) on April 28, 2011. Most of the rainfall was occurring at moderate rates however, there were pockets of very heavy rainfall in Virginia, North Carolina, South Carolina, Georgia and Alabama where rain was falling at a rate of 2 inches (50 millimeters) per hour.

Tornadoes associated with this extremely unstable weather caused the deaths of at least 128 people in Alabama and 15 in Georgia.

TRMM data was also used to generate a 3-D look at the storm. TRMM's Precipitation Radar (PR) data was used by Hal Pierce of SSAI at NASA's Goddard Space Flight Center in Greenbelt, Md. to create a 3-D structure of those storms. The image Pierce created is a TRMM radar vertical cross section that shows some of these violent storms reached to incredible heights of almost 17 km (~10.6 miles).

Bathed in xenon lights, space shuttle Endeavour moves along the crawlerway from the Vehicle Assembly Building to Launch Pad 39A at NASA's Kennedy Space Center in Florida. Riding atop a crawler-transporter attached to its external fuel tank and solid rocket boosters, Endeavour's last scheduled 3.4-mile trek to the pad, known as "rollout," took just less than eight hours. Image credit: NASA/Terry Zaperac


Space shuttle Endeavour has spent 19 years pushing boundaries, and its final mission will allow that legacy to live on.

Among Endeavour’s missions was the first to include four spacewalks, and then the first to include five. Its STS-67 mission set a length record almost two full days longer than any shuttle mission before it. Its airlock is the only one to have seen three spacewalkers exit through it for a single spacewalk. And in its cargo bay, the first two pieces of the International Space Station were joined together.

On STS-134, however, it will help push boundaries of a different sort as it delivers a new, cutting edge science experiment to the space station: the Alpha Magnetic Spectrometer.

“The AMS is an amazing story all by itself,” said Gary Horlacher, lead space shuttle flight director for the mission. “They’ve been working on this for well over 15 years now. It’s bigger than a VW bug, and it will be able to look at things that the other observatories aren’t even looking at. It is, without a doubt, going to continue to rewrite our future as we try to figure out our past.”

The Alpha Magnetic Spectrometer is a state-of-the-art, high energy particle physics experiment built in Geneva by a collaboration of 16 different countries. It will search for clues on what the universe is made of and how it began, the origin of dark matter, antimatter and strangelets, pulsars, blazers and gamma ray bursters. And that’s just what the scientists know to look for.

“I am quite confident that once we start measuring data in space, we will find things that we never anticipated,” NASA’s AMS Project Manager Trent Martin said. “And those things will lead to potential new areas of study, new areas of science and maybe even redefine some of the physics books.”

CAPE CANAVERAL — This day may begin with the Brits, but it'll end in a most American way, with a shuttle launch attended by the first family and recovering U.S. Rep. Gabrielle Giffords.

President Barack Obama and his family are expected to fly to Kennedy Space Center for today's Endeavour launch. The Arizona congresswoman arrived Wednesday and will watch her husband take off into space from a private location.

At 3:47 p.m., Endeavour is expected to thunder into the sky.

There's a 70 percent chance it will leave as planned, NASA officials said Thursday.

Giffords' husband, Navy Capt. Mark Kelly, will lead the six-man shuttle crew to the International Space Station. During the 14-day mission, they'll deliver supplies, including the Alpha Magnetic Spectrometer-2, a particle detector that scientist hope will detect dark matter and antimatter.

Endeavour is the next-to-last launch before NASA's shuttle program winds down. The space shuttle Atlantis is expected to launch on June 28.

Though all the tickets for on-base viewing of Endeavour's launch were snatched up long ago, there are other popular viewing spots:

• In Titusville, along the Indian River on U.S. 1.

• The Beachline Expressway (State Road 528), especially along the Bennett Causeway.

• Off Highway A1A along the Atlantic Ocean in Cocoa Beach.

• Jetty Park at Port Canaveral.

Beware: Authorities say the expected crowds could rival those of the most-attended launches in history. Some officials estimate that between 500,000 to 750,000 will descend upon the Space Coast.

So there's always the other option:

At 3:47 p.m., look east.

Information from Times wires was used in this report. Jessica Vander Velde can be reached at jvandervelde@sptimes.com or (813) 226-3433.

Six astronauts are scheduled to lift off into space on shuttle Endeavour’s final mission today, reminding the world of the United States’ continued leadership in space. And while Endeavour will complete its last voyage, the Obama administration’s commitment to human exploration remains as strong as ever.

American astronauts continue to live and work aboard the International Space Station 24 hours a day, seven days a week, 52 weeks a year, as they have for more than 10 years. And this critical research facility in low- Earth orbit will continue to be the anchor of our human spaceflight for the next decade.

We at NASA are committed to maintaining America’s leadership role in human exploration — and sending U.S. astronauts into space aboard American-made spacecraft.

It’s time for NASA to get out of the expensive business of owning and operating space transportation systems to service the International Space Station, and focus our limited resources on developing new vehicles to take us farther into deep space.

We recognize this is a difficult time for much of the devoted workforce that has made the shuttle program the incredible success it has been for three decades. However, this new approach will spur economic activity, create jobs and allow NASA to focus on the really hard stuff — such as sending humans to an asteroid or Mars.

President Obama’s fiscal year 2012 budget achieves these ambitious goals by supporting all the elements of a hard-won, bipartisan NASA Authorization Act. It’s a budget that will help the nation win the future through innovation, expanded technological capabilities and strengthened U.S. competitiveness in the global marketplace.

Funding for the final shuttle mission in June, STS-135, was included as part of the budget agreement the president reached with Congress recently, and the president has included a half-billion dollars in next year’s budget to pay the pension costs of thousands of dedicated shuttle workers.

These workers met their obligations to us, and now a grateful nation will uphold its end of the bargain.

 

CAPE CANAVERAL, Fla. | Rep. Gabrielle Giffords left hospitals behind Wednesday for the first time since her tragic shooting nearly four months ago and traveled to NASA territory for the next-to-last space shuttle launch with her husband in command.

“Gab- by is looking forward to some time away from the rehab center & the chance to see Captain Mark Kelly launch again!” Giffords’ staff posted on her Facebook page.

Endeavour is due to blast off at 2:47 p.m. CDT Friday with Kelly at the helm. 

Endeavour’s fuel tank, meanwhile, has an interesting story. The 10-year-old tank now sports 103 patches. It had been in a building in New Orleans when Hurricane Katrina hit in 2005; more than 100 nicks were made in foam. NASA says it’s perfectly safe to use.

Read more: http://www.kansascity.com/2011/04/27/2831881/rep-giffords-arrives-in-florida.html#ixzz1KtGgNlse

 

Troy Janisch, 43, from DeForest, is a member of the social media team at American Family Insurance national headquarters in Madison, and one of 150 bloggers chosen from more than 4,000 to attend the NASA Tweetup of the space shuttle Endeavor launch on April 29, 2011. Tom Buchheim

The ISS Progress 41 cargo craft backs away from the International Space Station after undocking Friday morning. Credit: NASA TV
The departure of an unpiloted Russian cargo craft Friday set the stage for the arrival of the next supply ship and a final visit from space shuttle Endeavour.

The ISS Progress 41 cargo craft, filled with trash and other unneeded items, undocked from the Pirs docking compartment at 7:41 a.m. EDT Friday as the International Space Station flew 220 miles over China. As the Progress slowly backed away from the station, Expedition 27 Commander Dmitry Kondratyev photographed the cargo craft through a window in the Russian segment of the orbiting complex to assess the condition of the rubber seals on its docking interface.

The Russian supply vehicle will remain in orbit a safe distance from the station for engineering tests before being commanded by flight controllers Tuesday to descend to a destructive re-entry into Earth’s atmosphere over the Pacific Ocean.

The departure of Progress 41 clears the way for the next unpiloted supply ship, ISS Progress 42, which is set to launch Wednesday from the Baikonur Cosmodrome in Kazakhstan. The new Progress will arrive at the station on April 29 at 10:29 a.m., just a little more than five hours before Endeavour launches to the station on its final trip into space. The shuttle’s STS-134 crew will deliver the Alpha Magnetic Spectrometer and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre.

Flight Engineer Ron Garan spent some time Friday preparing for the arrival of Endeavour as he reviewed the robotics operations involved in removing the Orbiter Boom Sensor System from the shuttle’s payload bay with Canadarm2 and handing it off to the shuttle’s robotic arm.

Meanwhile Flight Engineer Paolo Nespoli performed maintenance on the spacesuits that the STS-134 crew will wear during the four spacewalks planned when Endeavour visits the station. Nespoli performed a water dump and refill of the feedwater tanks and conducted maintenance on the cooling loops of the suits.

Garan and Nespoli joined Flight Engineer Cady Coleman as they continue to unload cargo from the “Johannes Kepler” Automated Transfer Vehicle-2. The European Space Agency supply ship, which delivered seven tons of cargo when it docked to the aft port of the Zvezda service module on Feb. 24, will be reloaded with trash and undocked from the station for disposal in late June.

Cosmonauts Andrey Borisenko and Alexander Samokutyaev, both flight engineers, participated in the Pneumocard experiment, which studies the adaptation of the crew’s cardiovascular system during long-duration spaceflight.

Over the weekend the station’s six residents will enjoy some light-duty time as they attend to some weekly housekeeping chores, perform voluntary science activities and continue their daily two-hour exercise regimen to stave off the physical effects associated with long-duration spaceflight.

 

Astronomers using NASA's Galaxy Evolution Explorer may be closer to knowing why some of the most massive stellar explosions ever observed occur in the tiniest of galaxies.

"It's like finding a sumo wrestler in a little 'Smart Car,'" said Don Neill, a member of NASA's Galaxy Evolution Explorer team at the California Institute of Technology in Pasadena, and lead author of a new study published in the Astrophysical Journal.

"The most powerful explosions of massive stars are happening in extremely low-mass galaxies. New data are revealing that the stars that start out massive in these little galaxies stay massive until they explode, while in larger galaxies they are whittled away as they age, and are less massive when they explode," said Neill. 

Over the past few years, astronomers using data from the Palomar Transient Factory, a sky survey based at the ground-based Palomar Observatory near San Diego, have discovered a surprising number of exceptionally bright stellar explosions in so-called dwarf galaxies up to 1,000 times smaller than our Milky Way galaxy. Stellar explosions, called supernovae, occur when massive stars -- some up to 100 times the mass of our sun -- end their lives. 

The Palomar observations may explain a mystery first pointed out by Neil deGrasse Tyson and John Scalo when they were at the University of Austin Texas (Tyson is now the director of the Hayden Planetarium in New York, N.Y.). They noted that supernovae were occurring where there seemed to be no galaxies at all, and they even proposed that dwarf galaxies were the culprits, as the Palomar data now indicate. 

Now, astronomers are using ultraviolet data from the Galaxy Evolution Explorer to further examine the dwarf galaxies. Newly formed stars tend to radiate copious amounts of ultraviolet light, so the Galaxy Evolution Explorer, which has scanned much of the sky in ultraviolet light, is the ideal tool for measuring the rate of star birth in galaxies. 

The results show that the little galaxies are low in mass, as suspected, and have low rates of star formation. In other words, the petite galaxies are not producing that many huge stars.

"Even in these little galaxies where the explosions are happening, the big guys are rare," said co-author Michael Rich of UCLA, who is a member of the mission team. 

In addition, the new study helps explain why massive stars in little galaxies undergo even more powerful explosions than stars of a similar heft in larger galaxies like our Milky Way. The reason is that low-mass galaxies tend to have fewer heavy atoms, such as carbon and oxygen, than their larger counterparts. These small galaxies are younger, and thus their stars have had less time to enrich the environment with heavy atoms. 

According to Neill and his collaborators, the lack of heavy atoms in the atmosphere around a massive star causes it to shed less material as it ages. In essence, the massive stars in little galaxies are fatter in their old age than the massive stars in larger galaxies. And the fatter the star, the bigger the blast that will occur when it finally goes supernova. This, according to the astronomers, may explain why super supernovae are occurring in the not-so-super galaxies.

"These stars are like heavyweight champions, breaking all the records," said Neill. 

Added Rich, "These dwarf galaxies are especially interesting to astronomers, because they are quite similar to the kinds of galaxies that may have been present in our young universe, shortly after the Big Bang. The Galaxy Evolution Explorer has given us a powerful tool for learning what galaxies were like when the universe was just a child." 

Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory in Pasadena manages the mission and built the science instrument. Caltech manages JPL for NASA. The mission was developed under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Centre National d'Etudes Spatiales (CNES) in France collaborated on this mission.

Graphics and additional information about the Galaxy Evolution Explorer are online at http://www.nasa.gov/galex and http://www.galex.caltech.edu .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney.clavin@jpl.nasa.gov

 

A newly found, buried deposit of frozen carbon dioxide -- dry ice -- near the south pole of Mars contains about 30 times more carbon dioxide than previously estimated to be frozen near the pole. Image credit: NASA/JPL-Caltech/Sapienza University of Rome/Southwest Research Institute

This cross-section view of underground layers near Mars' south pole is a radargram based on data from the Shallow Subsurface Radar (SHARAD) instrument on NASA's Mars Reconnaissance Orbiter. Image credit: NASA/JPL-Caltech/Sapienza University of Rome/Southwest Research Institute

These images from orbit show an area near Mars' south pole where coalescing or elongated pits are interpreted as signs that an underlying deposit of frozen carbon dioxide, or "dry ice," has been shrinking by sublimation. Image credit: NASA/JPL-Caltech/Univ. of Arizona

PASADENA, Calif. -- NASA's Mars Reconnaissance Orbiter has discovered the total amount of atmosphere on Mars changes dramatically as the tilt of the planet's axis varies. This process can affect the stability of liquid water, if it exists on the Martian surface, and increase the frequency and severity of Martian dust storms. 

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 about the Mars Reconnaissance Orbiter mission, visit http://www.nasa.gov/mro .

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov

Maria Martinez 210-522-3305
Southwest Research Institute, San Antonio, Texas
maria.martinez@swri.org

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov