Mars Orbiter Back at Full Strength
A THEMIS image showing entrances to possible Martian caves, dubbed the "seven sisters." Clockwise from upper-left: Dena, Chloe, Wendy, Annie, Abbey, Nikki and Jeanne. Arrows signify direction of solar illumination (I) and direction of North (N).
Credit: GE Cushing, TN Titus, JJ Wynne, USGS, USGS, Northern Arizona University, and PR Christensen of Arizona State University

A NASA probe circling Mars is back at full strength as researchers ponder its past views of possible cave entrances on the red planet?s surface.

The agency?s Mars Odyssey spacecraft resumed science operations this week after spending several days in ?safe mode? due to a Sept. 14 software glitch. While in safe mode, a precautionary configuration designed to preserve the orbiter?s health during a glitch, engineers on Earth methodically restored Odyssey?s onboard systems.

"The spacecraft reacted exactly as it was designed to for this condition," said Robert Mase, NASA?s Odyssey mission manager at the Jet Propulsion Laboratory in Pasadena, Calif., earlier this week.

Meanwhile, researchers are hoping to use the revived probe and other red planet orbiters to hunt for more cave-like pits akin to those found by Odyssey and the Mars Global Surveyor earlier this year. Dubbed the ?Seven Sisters,? the dark holes were discovered on a massive martian volcano dubbed Arsia Mons and range between 328 to 820 feet (100 to 250 meters) in diameter, mission managers said.

"They are cooler than the surrounding surface in the day and warmer at night," said Glen Cushing of U.S. Geological Survey's Astrogeology Team and Northern Arizona University in Flagstaff, Ariz., in a Friday statement. "Their thermal behavior is not as steady as large caves on Earth that often maintain a fairly constant temperature, but it is consistent with these being deep holes in the ground."

Researchers described Odyssey?s potential cave finds, which were previously reported on SPACE.com, in a recent online edition of the journal Geophysical Research Letters.

"Whether these are just deep vertical shafts or openings into spacious caverns, they are entries to the subsurface of Mars," said study co-author Tim Titus, of the U.S. Geological Survey, in a statement. "Somewhere on Mars, caves might provide a protected niche for past or current life, or shelter for humans in the future."

Because the martian Seven Sisters are perched high up on Arsia Mons, near Mars? tallest mountain, their extreme altitude would make their location a poor candidate to support future astronaut bases or possible microbial life, mission researchers said.

With Mars Odyssey now out of safe mode, the orbiter can also resume its role as a communications relay between NASA?s twin red planet rovers Spirit and Opportunity on the martian surface.

While Odyssey was unavailable, the rovers beamed their daily communication signals directly to Earth, NASA officials said. The orbiter launched towards Mars in 2001 and is partway through its second mission extension, they added.

Another planetary probe jointly run by NASA, the international Cassini spacecraft currently orbiting Saturn, is also back to work after its own safe mode session.

A power trip caused by a run-in with a cosmic ray put Cassini in safe mode on Sept. 11 after the probe?s flyby past Saturn?s moon Iapetus. The glitch delayed the spacecraft?s transmission of the flyby data by about a day and the probe was back to full operation by Sunday, NASA officials said.

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