Could Life Hide Inside Mars' Caves?

While one intrepid Mars rover goes crawling this month into its biggest crater yet, eyes from the Martian sky are capturing first views of caves, and making progress on some of the most tantalizing question facing Red planet researchers.

NASA is highlighting a pair of interesting reports based on photos and data drawn from its Orbiter probe, drawing tentative conclusions about what appear to be unusual cave structures, and waterlike drainage patterns that successive photos of the same area show have developed over the past decade.

The drainage gullies had initially raised hopes that researchers had found evidence of present-day liquid flow on the planet's surface. Take a look at the first picture included here (color has been enhanced to display the patterns) and you'll see why – its resemblance to run-off from mountain gullies is striking.

Scientists have seen these patterns develop, since before-and-after photographs of the area dating back to an earlier mission in 1999 have seen the patterns evolve. However, the most recent evidence from the
Mars Reconnaissance Orbiter seems to indicate that the flows were in fact landslides, composed of dry, loose material.

That doesn't crush the water theory altogether, however; just pushes it back a few thousand millennia. Sez NASA:

Other gullies, however, offer strong evidence of liquid water flowing on Mars within the last few million years, although perhaps at a different phase of repeating climate cycles. Mars, like Earth, has periodic changes in climate due to the cycles related to the planets'
tilts and orbits. Some eras during the cycles are warmer than others.
These gullies are on slopes too shallow for dry flows, and images from
MRO's high-resolution camera show clear indicators of liquid flows, such as braided channels and terraces within the gullies.

Another set of reports and photos details an odd set of circles high on one of Mar's tallest mountains, found and analyzed by the Mars Odyssey probe to be cooler than the surrounding surface by day, and warmer at night. Researchers have concluded that the circles are cave skylights –
or at least deep holes – unlike anything seen before.

Caves in this area could have been created by volcanic stresses and faults opening underground spaces, with portions of the weakened roofs ultimately falling in, researchers said. These particular ones, dubbed
“The Seven Sisters,” are likely too high to be candidates for finding interesting organic material, but scientists' imaginations have been sparked:

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

NASA Orbiter Provides Insights About Mars Water and Climate[NASA press release]
NASA Orbiter Finds Possible Cave Skylights on Mars [NASA press release]

(Photo one: Gully channels in the southern highlands of Mars. Credit:
NASA/JPL/University of Arizona. Photo two. Entrances to seven possible caves. Credit: NASA/JPL-Caltech/ASU/USGS)