A Puddle of . . . What?

Many of those following the Mars Exploration Rover mission have puzzled over a recent photograph that appears to show a shallow pool of water or mud in the foreground.





The finding is similar to the so-called "Magic Carpet" encountered by Spirit shortly after bouncing to a landing. But whereas the possible moisture at the Spirit landing site appeared to take the form of subsurface mud, the "puddle" viewed by Opportunity looks remarkably like standing water -- a supposed impossibility on a cold, low-pressure world like Mars. So what does the image show?




Possible subsurface water leaking onto the Martian surface.


Although I'm not ruling out water, ice or mud (or some combination thereof), it's likely we're seeing a deposit of fine dust. A shallow film of dust would help explain the puddle's smooth surface texture. On the other hand, recent claims of volcanic activity on Mars, and the relatively high-pressure depths of the Valles Marineris canyon system, supply mechanisms that could spawn short-lived flows. If the Opportunity image does show water, liquid or ice, then we're perhaps incredibly lucky to see it before it could boil away into the atmosphere.

Occam's Razor would suggest we're seeing particulates wafted into place by wind, but our history of discovery on the Red Planet advises against premature conclusions.