Washington, May 23 : NASA's Phoenix Mars lander, which would descent on the Martian surface on May 25, would analyze the red sand on the planet to find evidence that liquid water, generally agreed to be a prerequisite of life, once pooled there. Examination of the Martian soil is part of the task of a sophisticated on-board instrument package known as MECA, for Microscopy, Electrochemistry, and Conductivity Analyzer (MECA).
Two microscopes are part of this package, and it is their close-up views that might supply conclusive evidence for a watery past.
According to John Marshall, a planetary geologist with the Carl Sagan Center at the SETI Institute, "This very detailed examination of the sand grains could supply a vital clue as to whether Mars was ever conducive to life, or if microscopic life might still have a foothold there."
Imaging is a big part of the Phoenix mission, with a stereo camera placed on the main deck of the lander to provide landscape views and the camera on the robotic arm to see sand and pebbles.
But the MECA has both a low-power optical microscope for scrutinizing a field-of-view only millimeters in size, and an atomic force microscope able to make a "topographic map" of soil particles with detail a thousand times finer than its optical counterpart.
The atomic force microscope works by means of a tiny stylus that "feels" its way over the sample.
The size of the soil particles, as well as their shape and surface texture, are all indicators of whether or not liquid water was present on the Red Planet.
Within the MECA package are four box-like receptacles, or reaction chambers, each the size of a demitasse cup.
Their inside walls are covered, polka-dot like, with 24 sensors. As Phoenix's robotic arm pulls soil off the landscape, it deposits some samples into these water-filled chambers.
"Adding these soil samples to water allows us to look for is soluble salts," said Quinn. "Finding these would help establish what the prior water history was at the landing site, and might give an indication if this area of Mars was habitable," he added.
"In a hundred years, our view of the Red Planet has gone from a small, ruddy dot imperfectly seen in an Earth-bound telescope to a detailed scrutiny of the tiniest irregularities on a grain of Martian sand," said Marshall.