Digging Deep on Mars

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While TEGA can't tell the difference between organics resulting from chemical processes and those made by living organisms, it could at least provide enough information to allow researchers to decide whether its landing area is worthy of later exploration by landers equipped to search directly for traces of life. "If this is a region where organics can survive, it might be a region one could go back to with a roving mission to see if there are indications of life or not," Boynton says.

Although it's a long shot, TEGA might also be able to find more direct traces of life. Three different groups have reported the detection of methane gas in the Martian air, although the amounts are low and the evidence remains controversial. With luck, the Phoenix device might pick up those traces, especially if, as some researchers suggest, they may sometimes reach higher concentrations in some places. Methane in the air, since it breaks down quickly, would be a clear sign of a very active process--either current volcanism, which has not been detected there, or the metabolism of living organisms.

Phoenix, a project led by University of Arizona planetary scientist Peter Smith, will be the first planetary probe whose operations will be run from a university-based control room rather than a space-agency center. This is a step toward making planetary exploration a normal, operational process and taking it beyond the experimental development phase. A similar setup has worked well for the Chandra X-ray Observatory, which is run from a control center in Cambridge, MA, and operated by MIT.

Phoenix also represents an unusually inexpensive approach to such a complex mission, partly because it was able to make use of spacecraft and instruments developed for the Mars Polar Lander, which crash-landed in 2002, and from the Mars Surveyor Lander, a project that was canceled by NASA in 2001. This rebirth with parts from lost missions gave the new mission its name.

Scientists have been puzzled by Mars's ruddy soil ever since the Viking mission in 1976 investigated the planet from ground level for the first time. The results from the twin Viking landers, which have been heatedly debated ever since, suggested the presence of some powerful oxidizing agent on the soil surface that very quickly decomposes any organic compounds there--an environment highly toxic for life.

But many scientists suspect that just a few inches below the surface, things may be very different. Radar and gamma-ray inspections from orbiting spacecraft have revealed a layer of subsurface ice on much of the planet, in some places just a few inches deep. In the near-polar region where Phoenix will land, ice may extend more than a half-mile down, and parts of it may occasionally melt in certain seasons. It's a place where, if life ever gained a toehold on Mars, its last straggling microbes may have survived for eons, and where some might even persist today.