Feb 8 2012
From The Space Library
RELEASE: 12-048 NASA MISSION TAKES STOCK OF EARTH'S MELTING LAND ICE
WASHINGTON -- In the first comprehensive satellite study of its kind, a University of Colorado at Boulder-led team used NASA data to calculate how much Earth's melting land ice is adding to global sea level rise. Using satellite measurements from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE), the researchers measured ice loss in all of Earth's land ice between 2003 and 2010, with particular emphasis on glaciers and ice caps outside of Greenland and Antarctica. The total global ice mass lost from Greenland, Antarctica and Earth's glaciers and ice caps during the study period was about 4.3 trillion tons (1,000 cubic miles), adding about 0.5 inches (12 millimeters) to global sea level. That's enough ice to cover the United States 1.5 feet (0.5 meters) deep. "Earth is losing a huge amount of ice to the ocean annually, and these new results will help us answer important questions in terms of both sea rise and how the planet's cold regions are responding to global change," said University of Colorado Boulder physics professor John Wahr, who helped lead the study. "The strength of GRACE is it sees all the mass in the system, even though its resolution is not high enough to allow us to determine separate contributions from each individual glacier." About a quarter of the average annual ice loss came from glaciers and ice caps outside of Greenland and Antarctica (roughly 148 billion tons, or 39 cubic miles). Ice loss from Greenland and Antarctica and their peripheral ice caps and glaciers averaged 385 billion tons (100 cubic miles) a year. Results of the study will be published online Feb. 8 in the journal Nature. Traditional estimates of Earth's ice caps and glaciers have been made using ground measurements from relatively few glaciers to infer what all the world's unmonitored glaciers were doing. Only a few hundred of the roughly 200,000 glaciers worldwide have been monitored for longer than a decade. One unexpected study result from GRACE was the estimated ice loss from high Asian mountain ranges like the Himalaya, the Pamir and the Tien Shan was only about 4 billion tons of ice annually. Some previous ground-based estimates of ice loss in these high Asian mountains have ranged up to 50 billion tons annually. "The GRACE results in this region really were a surprise," said Wahr, who also is a fellow at the University of Colorado-headquartered Cooperative Institute for Research in Environmental Sciences. "One possible explanation is that previous estimates were based on measurements taken primarily from some of the lower, more accessible glaciers in Asia and extrapolated to infer the behavior of higher glaciers. But unlike the lower glaciers, most of the high glaciers are located in very cold environments and require greater amounts of atmospheric warming before local temperatures rise enough to cause significant melting. This makes it difficult to use low-elevation, ground-based measurements to estimate results from the entire system." "This study finds that the world's small glaciers and ice caps in places like Alaska, South America and the Himalayas contribute about .02 inches per year to sea level rise," said Tom Wagner, cryosphere program scientist at NASA Headquarters in Washington. "While this is lower than previous estimates, it confirms that ice is being lost from around the globe, with just a few areas in precarious balance. The results sharpen our view of land ice melting, which poses the biggest, most threatening factor in future sea level rise." The twin GRACE satellites track changes in Earth's gravity field by noting minute changes in gravitational pull caused by regional variations in Earth's mass, which for periods of months to years is typically because of movements of water on Earth's surface. It does this by measuring changes in the distance between its two identical spacecraft to one-hundredth the width of a human hair. The GRACE spacecraft, developed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., and launched in 2002, are in the same orbit approximately 137 miles (220 kilometers) apart.
RELEASE: 12-049 NASA'S CHANDRA FINDS MILKY WAY'S BLACK HOLE GRAZING ON ASTEROIDS
WASHINGTON -- The giant black hole at the center of the Milky Way may be vaporizing and devouring asteroids, which could explain the frequent flares observed, according to astronomers using data from NASA's Chandra X-ray Observatory. For several years Chandra has detected X-ray flares about once a day from the supermassive black hole known as Sagittarius A*, or "Sgr A*" for short. The flares last a few hours with brightness ranging from a few times to nearly one hundred times that of the black hole's regular output. The flares also have been seen in infrared data from ESO's Very Large Telescope in Chile. "People have had doubts about whether asteroids could form at all in the harsh environment near a supermassive black hole," said Kastytis Zubovas of the University of Leicester in the United Kingdom, and lead author of the report appearing in the Monthly Notices of the Royal Astronomical Society. "It's exciting because our study suggests that a huge number of them are needed to produce these flares." Zubovas and his colleagues suggest there is a cloud around Sgr A* containing trillions of asteroids and comets, stripped from their parent stars. Asteroids passing within about 100 million miles of the black hole, roughly the distance between the Earth and the sun, would be torn into pieces by the tidal forces from the black hole. These fragments then would be vaporized by friction as they pass through the hot, thin gas flowing onto Sgr A*, similar to a meteor heating up and glowing as it falls through Earth's atmosphere. A flare is produced and the remains of the asteroid are swallowed eventually by the black hole. "An asteroid's orbit can change if it ventures too close to a star or planet near Sgr A*," said co-author Sergei Nayakshin, also of the University of Leicester. "If it's thrown toward the black hole, it's doomed." The authors estimate that it would take asteroids larger than about six miles in radius to generate the flares observed by Chandra. Meanwhile, Sgr A* also may be consuming smaller asteroids, but these would be difficult to spot because the flares they generate would be fainter. These results reasonably agree with models estimating of how many asteroids are likely to be in this region, assuming that the number around stars near Earth is similar to the number surrounding stars near the center of the Milky Way. "As a reality check, we worked out that a few trillion asteroids should have been removed by the black hole over the 10-billion-year lifetime of the galaxy," said co-author Sera Markoff of the University of Amsterdam in the Netherlands. "Only a small fraction of the total would have been consumed, so the supply of asteroids would hardly be depleted." Planets thrown into orbits too close to Sgr A* also should be disrupted by tidal forces, although this would happen much less frequently than the disruption of asteroids, because planets are not as common. Such a scenario may have been responsible for a previous X-ray brightening of Sgr A* by about a factor of a million about a century ago. While this event happened many decades before X-ray telescopes existed, Chandra and other X-ray missions have seen evidence of an X-ray "light echo" reflecting off nearby clouds, providing a measure of the brightness and timing of the flare. "This would be a sudden end to the planet's life, a much more dramatic fate than the planets in our solar system ever will experience," Zubovas said. Very long observations of Sgr A* will be made with Chandra later in 2012 that will give valuable new information about the frequency and brightness of flares and should help to test the model proposed here to explain them. This work could improve understanding about the formation of asteroids and planets in the harsh environment of Sgr A*. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.
RELEASE: 12-046 NASA SEEKS PROPOSALS FOR GREEN PROPELLANT TECHNOLOGY DEMONSTRATIONS
WASHINGTON -- NASA is seeking technology demonstration proposals for green propellant alternatives to the highly toxic fuel hydrazine. As NASA works with American companies to open a new era of access to space, the agency seeks innovative and transformative fuels that are less harmful to our environment. Hydrazine is an efficient and ubiquitous propellant that can be stored for long periods of time, but is also highly corrosive and toxic. It is used extensively on commercial and defense department satellites as well as for NASA science and exploration missions. NASA is looking for an alternative that decreases environmental hazards and pollutants, has fewer operational hazards and shortens rocket launch processing times. "High performance green propulsion has the potential to significantly change how we travel in space," said Michael Gazarik, director of NASA's Space Technology Program at the agency's headquarters in Washington. "NASA's Space Technology Program seeks out these sort of cross-cutting, innovative technologies to enable our future missions while also providing benefit to the American space industry. By reducing the hazards of handling fuel, we can reduce ground processing time and lower costs for rocket launches, allowing a greater community of researchers and technologists access to the high frontier." Beyond decreasing environmental hazards and pollutants, promising aspects of green propellants also include reduced systems complexity, fewer operational hazards, decreased launch processing times and increased propellant performance. Maturing a space technology, such as green propellants, to mission readiness through relevant environment testing and demonstration is a significant challenge from a cost, schedule and risk perspective. NASA has established the Technology Demonstration Missions Program to perform this function, bridging the gap between laboratory confirmation of a technology and its initial use on an operational mission. NASA anticipates making one or more awards in response to this solicitation, with no single award exceeding $50 million. Final awards will be made based on the strength of proposals and availability of funds. The deadline for submitting proposals is April 30. The Technology Demonstration Missions Program is managed by NASA's Marshall Space Flight Center in Huntsville, Ala
MEDIA ADVISORY: M12-022 NASA OFFICIALS TO DISCUSS FISCAL YEAR 2013 BUDGET
WASHINGTON -- NASA Administrator Charles Bolden will brief reporters about the agency's fiscal year 2013 budget at 2 p.m. EST on Monday, Feb. 13. The news conference will take place in the James E. Webb Memorial Auditorium at NASA Headquarters, located at 300 E St. SW, in Washington. NASA Chief Financial Officer Elizabeth Robinson will join Bolden. The news conference will be broadcast live on NASA Television and the agency's website. Questions will be taken from news media representatives at headquarters and NASA field centers. For the first time, NASA is inviting 20 of its Twitter followers to join reporters for the budget news conference. Tweeps interested in being a part of this event and asking questions can sign-up online. Registration will be open for 24 hours beginning at 5 p.m. on Wednesday, Feb. 8. Selected participants will be notified on Friday, Feb. 10. During the news conference, NASA also will take as many questions as possible submitted via Twitter using the hashtag #askNASA. After the overview briefing on NASA's fiscal year 2013 budget, the associate administrators of the mission directorates and NASA's chief technologist will hold individual teleconferences to discuss the budget's impact on their specific areas.
