'Another New Mars': NASA Orbiter Ready for Red Planet Science

This enhanced-color view shows gullies in an unnamed crater in the Terra Sirenum region of Mars. It is a sub-image from a larger view imaged by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter on Oct. 3, 2006. This scene is about 254 meters (about 830 feet) wide. CREDIT: NASA/JPL/Univ. of Arizona.

NASA's latest spacecraft to orbit Mars has already found new clues to the red planet's changing environment, and the best is yet to come, mission managers said Monday.

The Mars Reconnaissance Orbiter (MRO) is still weeks away from beginning its planned science mission, but the immense probe has thrilled scientists with initial images and data pointing to a variable polar environment, ancient soaking events that produced clays, and relatively new--geologically speaking--gullies carved into the shadowed rim of a southern crater.

"We have another new Mars," said Steve Saunders, MRO program scientist at NASA's Washington D.C. headquarters, in a mission briefing. "Every time we go to Mars with a new set of instruments, we see a different planet."

Over the last two weeks, Mars researchers tested MRO's complex suite of instruments. During the instrument checks the MRO instruments found evidence of changes at Mars' north polar ice cap, as well as relatively young gullies, mission scientists said.

"During our check-out period we were deliberately picking places that we knew about and that would help us in our [instrument] calibration," said NASA's Rich Zurek, MRO project scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, California. "Now we're going to find new areas as well."

MRO used its imaging spectrometer to examine a 3,500-foot (1,066-meter) cliff in Chasma Boreale, an expansive valley that juts into Mars' northern polar ice cap. The orbiter found a cap of ice covering atop a series of layers that alternate between ice-rich and dust-rich bands, suggesting relatively recent environmental and climate changes.

"At the north polar ice cap over the last 100,000 or so years, there's been a really dynamic history of changes reported in layers of ice much like we would determine Earth's climate change and looking at a core of ice from Greenland," said Scott Murchie, of Johns Hopkins University's Applied Physics Laboratory, who serves as lead scientist for MRO's imaging spectrometer.

The imaging spectrometer also spied a wide range of mineral-rich clays on Mars in a region known as Mawrth Valles; some rich in iron while others nearby contained aluminum.

"Clay tells us that the surface was wet, and differences in the mineralogy tells us how the environment may have been different from place to place," Murchie said, adding that differences in clay composition can indicate variations in water temperature, salinity and other characteristics in the site's past. "What this is telling us is that on length scales of just a few hundred yards, the conditions were varying significantly enough that entirely different kinds of minerals were forming."

MRO's High Resolution Imaging Science Experiment (HiRISE) camera--an all-seeing eye so powerful it can resolve objects the size of people and recently photographed the NASA rover Opportunity on the rim of Victoria Crater [image]--also found evidence of channels around Mawrth Valles to support its ancient watery history, researchers said.

HiRISE also photographed a series of young gullies etched into the shadowed, frost-ridden wall of an unnamed Martian crater in the Terra Sirenum region.

"What impresses me most is that this is really a system of gullies, this is a complex landform," said Alfred McEwen, HiRISE principal investigator at the University of Arizona, adding that they may have been carved by flowing water in the past. "The big question here is, 'Is water seeping to the surface today?' and right now we don't have a smoking gun."

MRO has been circling Mars since it arrived at the red planet in March, but only settled into its final science orbit last month. Launched on Aug. 12, 2005, the spacecraft carries enough fuel to last through 2018. Full science operations will begin Nov. 7 after the red planet has passed behind the Sun.

The orbiter is expected to add new chapters to the story of Mars' watery history and help scientists identify potential landing sites for future red planet missions.

"We're just at the start of our data acquisition period and it's a little daunting to think that, very soon, we'll be opening up a fire hose of data from the spacecraft," Zurek said. "Our appetites are whetted and we're excited to get started."

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