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Phoenix Mars Lander
Shortly after NASA’s Phoenix lander settles onto Mars’ frigid, northern plains on May 25, it will undertake what is literally a microscopic examination of the red sand beneath its feet. By doing so, it may find evidence that liquid water – generally agreed to be a prerequisite of life – once pooled here.
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. On the main deck of the lander is a stereo camera that will provide landscape views. The camera on the robotic arm can 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.
- Visit the official site
- Read the entire press release
- Bumpy Road to Mars, I (article)
- Bumpy Road to Mars, II (article)
| Dr. John Marshall Carl Sagan Center Principal Investigator |
Dr. Richard Quinn Carl Sagan Center Principal Investigator |
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“If you see little clay particles,” Marshall notes, “you say ah, hah! There’s been aqueous weathering here – chemical alteration of the grains. It would be just like the clay you find in your back yard.” |
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Marshall’s job is to interpret close-ups from the optical microscope from a geologic perspective. 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. 
Richard Quinn, also at the SETI Institute’s Carl Sagan Center, is using MECA instruments to do a different kind of soil analysis: using the type of wet chemistry you may remember from high school. 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..| View the Phoenix Lander simulation | Links | |