Mar 9 2010
From The Space Library
RELEASE: 10-033
PLUTO'S WHITE, DARK-ORANGE AND CHARCOAL-BLACK TERRAIN CAPTURED BY NASA'S HUBBLE
WASHINGTON -- NASA has released the most detailed and dramatic images ever taken of the distant dwarf planet Pluto. The images from NASA's Hubble Space Telescope show an icy, mottled, dark molasses-colored world undergoing seasonal surface color and brightness changes. Pluto has become significantly redder, while its illuminated northern hemisphere is getting brighter. These changes are most likely consequences of surface ice melting on the sunlit pole and then refreezing on the other pole, as the dwarf planet heads into the next phase of its 248-year-long seasonal cycle. Analysis shows the dramatic change in color took place from 2000 to 2002. The Hubble pictures confirm Pluto is a dynamic world that undergoes dramatic atmospheric changes not simply a ball of ice and rock. These dynamic seasonal changes are as much propelled by the planet's 248-year elliptical orbit as by its axial tilt. Pluto is unlike Earth, where the planet's tilt alone drives seasons. Pluto's seasons are asymmetric because of its elliptical orbit. Spring transitions to polar summer quickly in the northern hemisphere, because Pluto is moving faster along its orbit when it is closer to the sun. Ground-based observations, taken in 1988 and 2002 show the mass of the atmosphere doubled during that time. This may be because of warming and melting nitrogen ice. The new Hubble images are giving astronomers essential clues about the seasons on Pluto and the fate of its atmosphere. When the Hubble pictures taken in 1994 are compared to those of 2002 and 2003, astronomers see evidence that the northern polar region has gotten brighter, while the southern hemisphere darkened. These changes hint at very complex processes affecting the visible surface. The images will help planetary astronomers interpret more than three decades of Pluto observations from other telescopes. "The Hubble observations are the key to tying together these other diverse constraints on Pluto and showing how it all makes sense by providing a context based on weather and seasonal changes, which opens other new lines of investigation, says principal investigator Marc Buie of the Southwest Research Institute in Boulder, Colo. These Hubble images, taken by the Advanced Camera for Surveys, will remain the sharpest view of Pluto until NASA's New Horizons probe is within six months of its flyby during 2015. The Hubble images are invaluable for picking the planet's most interesting hemisphere for imaging by the New Horizons probe. New Horizons will pass by Pluto so quickly that only one hemisphere will be photographed in detail. Particularly noticeable in the Hubble images is a bright spot that has been independently noted to be unusually rich in carbon monoxide frost. It is a prime target for New Horizons. Everybody is puzzled by this feature, Buie said. New Horizons will get an excellent look at the boundary between this bright feature and a nearby region covered in pitch-black surface material. "The Hubble images also will help New Horizons scientists better calculate the exposure time for each Pluto snapshot which is important for taking the most detailed pictures possible, Buie said. With no chance for re-exposures, accurate models for the surface of Pluto are essential for properly exposed images. The Hubble images surface variations a few hundred miles across that are too coarse for understanding surface geology. But in terms of surface color and brightness, Hubble reveals a complex-looking world with white, dark-orange and charcoal-black terrain. The overall color is believed to be a result of ultraviolet radiation from the distant sun breaking up methane present on Pluto's surface, leaving behind a dark and red-carbon-rich residue. The Hubble images are a few pixels wide. Through a technique called dithering, multiple, slightly offset pictures are combined through computer-image processing to synthesize a higher-resolution view than can be seen in a single exposure. "This has taken four years and 20 computers operating continuously and simultaneously to accomplish, Buie said. Buie developed the special algorithms to sharpen the Hubble data. He plans to use Hubble's new Wide Field Camera 3 to make additional observations prior to the arrival of New Horizons. For Hubble information and images, visit: http://www.nasa.gov/hubble
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RELEASE: 10-016
ROVER GIVES NASA AN OPPORTUNITY TO VIEW INTERIOR OF MARS
PASADENA, Calif. -- NASA's Mars exploration rover Opportunity is allowing scientists to get a glimpse deep inside Mars. Perched on a rippled Martian plain, a dark rock not much bigger than a basketball was the target of interest for Opportunity during the past two months. Dubbed Marquette Island, the rock is providing a better understanding of the mineral and chemical makeup of the Martian interior. "Marquette Island is different in composition and character from any known rock on Mars or meteorite from Mars, said Steve Squyres of Cornell University in Ithaca, N.Y. Squyres is principal investigator for Opportunity and its twin, Spirit. It is one of the coolest things Opportunity has found in a very long time. During six years of roving, Opportunity has found only one other rock of comparable size that scientists conclude was ejected from a distant crater. The rover studied the first such rock during its initial three-month mission. Called Bounce Rock, that rock closely matched the composition of a meteorite from Mars found on Earth. Marquette Island is a coarse-grained rock with a basalt composition. The coarseness indicates it cooled slowly from molten rock, allowing crystals time to grow. This composition suggests to geologists that it originated deep in the crust, not at the surface where it would cool quicker and have finer-grained texture. "It is from deep in the crust and someplace far away on Mars, though exactly how deep and how far we can't yet estimate, said Squyres. The composition of Marquette Island, as well as its texture, distinguishes it from other Martian basalt rocks that rovers and landers have examined. Scientists first thought the rock could be another in a series of meteorites that Opportunity has found. However, a much lower nickel content in Marquette Island indicates a Martian origin. The rock's interior contains more magnesium than in typical Martian basalt rocks Spirit has studied. Researchers are determining whether it might represent the precursor rock altered long ago by sulfuric acid to become the sulfate-rich sandstone bedrock that blankets the region of Mars that Opportunity is exploring. "It's like having a fragment from another landing site, said Ralf Gellert of the University of Guelph, in Ontario, Canada. Gellert is lead scientist for the alpha particle X-ray spectrometer on Opportunity's robotic arm. With analysis at an early stage, we're still working on some riddles about this rock. The rover team used Opportunity's rock abrasion tool to grind away some of Marquette Island's weathered surface and expose the interior. This was the 38th rock target Opportunity has ground into, and one of the hardest. The tool was designed to grind into one Martian rock, and this rock may not be its last. "We took a conservative approach on our target depth for this grind to ensure we will have enough of the bit left to grind the next hard rock that Opportunity comes across, said Joanna Cohen of Honeybee Robotics Spacecraft Mechanisms Corp., in New York, which built and operates the tool. Opportunity currently is about 30 percent of the way on a 12-mile trek begun in mid-2008 from a crater it studied for two years. It is en route toward a much larger crater, Endeavour. The rover traveled 3.3 miles in 2009, farther than in any other year on Mars. Opportunity drove away from Marquette Island on Jan. 12. "We're on the road again, said Mike Seibert, a rover mission manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. The year ahead will include lots more driving, if all goes well. We'll keep pushing for Endeavour crater but watch for interesting targets along the way where we can stop and smell the roses. Since landing on Mars in 2004, Opportunity has made numerous scientific discoveries, including the first mineralogical evidence that Mars had liquid water. After working 24 times longer than originally planned, Opportunity has driven more than 11 miles and returned more than 133,000 images. JPL manages the rovers for NASA's Science Mission Directorate in Washington.
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