Curiosity image of wheel – coated with Mars mud?
Credit: NASA/JPL

There is increasing discussion and debate concerning the exploration of Mars and how best to search for past/present life on the Red Planet.

One element of the deliberation is what constitutes a “Special Region” on Mars.

This series of images spans a period of 15 weeks shows a pair of fresh, middle-latitude craters on Mars. The bright material is water ice that was uncovered by the meteorite impact. Sublimation of the ice during the Martian summer leaves behind a dust layer that gradually thickens to the point where it obscures the ice. The impact responsible for these craters had not yet occurred by June 4, 2008, but had occurred by Aug. 10, 2008.
Credit: NASA/JPL-Caltech/University of Arizona

A Special Region is a region classified by the Committee on Space Research (COSPAR) where terrestrial organisms might readily propagate, or thought to have a high potential for existence of Martian life forms. This is understood to apply to a region on the Red Planet where liquid water occurs, or can occasionally happen, centered on our current understanding of requirements for life.

Impact craters

“I think many of the recent Martian meteorite impact craters imaged by Mars Reconnaissance Orbiter showing white ice in the interior of freshly exposed craters and their ejecta blanket should give us pause as to what ‘Special Regions’ on Mars are,” says Barry E. DiGregorio, director for the International Committee Against Mars Sample Return (ICAMSR). “In fact, every time I look into the night sky and see Mars,” he adds, “I think I am looking at a ‘Special Region.’”

The bright material conspicuous in this image was excavated from below the surface and deposited nearby by a 2008 impact that dug a crater about 8 meters (26 feet) in diameter. The extent of the bright patch was large enough for the Compact Reconnaissance Imaging Spectrometer for Mars, an instrument on NASA’s Mars Reconnaissance Orbiter, to obtain information confirming the material to be water ice.
Credit: NASA/JPL-Caltech/University of Arizona

DiGregorio suggests that no one at NASA can be sure that a rover or lander has not been inadvertently sent to a Special Region where wet zones persist.

“That’s because we apparently can’t detect the nearness of small amounts of evaporating water ice moving through the top soil or regolith,” DiGregorio notes.

Credit: NASA/JPL

Wheel proof – wet soil?

To enhance his case, DiGregorio points to images relayed from NASA’s Curiosity Mars rover. The images were acquired via the robot’s Mastcam camera on Sol’s 528-532.



“As you can see, the ‘soil’ adhering to the wheels is mud-like and wet – similar to a wet clay. So here you have an incident where Curiosity drove right over the top of a Special Region zone and it went unreported – until now,” DiGregorio concludes.


Responds John Rummel of the SETI Institute: “It is interesting that surface material can cling to the wheels of Curiosity, but it doesn’t need to be ‘wet’ to do that. The material has been compacted by a one-ton rover! And recall that a similar ‘clinginess’ was seen with subsurface samples taken by the Phoenix Mars lander back in 2008. At the time, the clingy soil became loose after the sample was left in the sun for awhile, possibly because that affected the hygroscopic nature of salts in the sample. Such material would likely be too salty for microbes even if ‘damp’ due to low water activity, but perhaps not always.’

Murray Buttes and Mars explorer.
Artwork credit: Sean Doran



The pages of the Astrobiology journal have served as the epicenter of new, on-going dialogue regarding future exploration of Mars and the search for life on that distant world.

Go to:

Searching for Life on Mars Before It Is Too Late

Four Fallacies and an Oversight: Searching for Martian Life

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