080711 First success with Phoenix soil probe and atomic force microscope

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First success with Phoenix soil probe and atomic

force microscope
BY DR EMILY BALDWIN
ASTRONOMY NOW

Posted: July 11, 2008

NASA's Phoenix Mars Lander has prodded Martian soil with its Thermal and Electrical Conductivity Probe (TECP) for the first time, and has begun using a microscope that examines the shapes of tiny soil particles by touching them.

The four spikes of the TECP instrument near the Martian soil appear as shadows in this image taken on July 8. The spikes are 1.5 centimetres long and will assess how easily heat and electricty move through the soil. Image: NASA/JPL-Caltech/University of Arizona/Max Planck Institute.

Held up in the air, the TECP has already provided assessment of water vapour in the Martian atmosphere, but for the first time in the mission its 1.5 centimetre long fork-like probes were pushed into undisturbed soil this week, as a validation test of the insertion procedure, which will be followed up with 'real' experiments over the next few days. The TECP will be used to assess how easily heat and electricity move through the soil from one of the probe’s spikes to another, which will provide information about the nature of frozen or unfrozen water in the soil.

Phoenix has also returned the first image from its Swiss-made atomic force microscope, which can provide details of soil particle shapes as small as about 100 nanometers, less than one-hundredth the width of a human hair and about 20 times smaller than what can be resolved with Phoenix's optical microscope, which has already provided much higher magnification imaging than anything ever before seen on Mars. The TECP builds an image of the surface of a soil particle through its sensor, which rides up and down following the contour of the particle's surface, thus providing information about the target's shape.

"The same day we first touched a target with the thermal and electrical conductivity probe, we first touched another target with a needle about three orders of magnitude smaller - one of the tips of our atomic force microscope," says Michael Hecht of NASA's Jet Propulsion Laboratory, lead scientist for the suite of instruments on Phoenix that includes both the conductivity probe and the microscopy station.

This callibration image presents three-dimensional data from the atomic force microscope, showing details of a grooved substrate on the microscope station's sample wheel. It will be used as an aid for interpreting later images that will show shapes of tiny Martian soil particles. The 40 by 40 micron surface is small enough to fit on an eyelash. Image: NASA/JPL-Caltech/University of Arizona/University of Neuchatel.

The microscope’s first test touch this week was of the grooved substrate of the microscopy station's sample wheel, which will be used to hold soil particles in place for inspection by the microscope.

"It's just amazing when you think that the entire area in this image fits on an eyelash,” says Hecht. “I'm looking forward to exciting things to come."

Phoenix has now put to use all the capabilities of its Microscopy, Electrochemistry and Conductivity Analyser (MECA) suite of instruments. Researchers have already begun analysing data from the second sample of soil tested by MECA's wet chemistry laboratory, and are still working on the best method to gather a sample of Martian ice to analyse using the lander's Thermal and Evolved-Gas Analyser, which heats samples to sniff out the vapours contained within the sample.