As NASA's Phoenix Mars Lander excavates trenches, it also builds piles
with most of the material scooped from the holes. The piles, like this one
called "Caterpillar," provide researchers some information about the soil.
On Aug. 24, 2008, during the late afternoon of the 88th Martian day after
landing, Phoenix's Surface Stereo Imager took separate exposures through
its left eye and right eye that have been combined into this stereo view.
The image appears three dimensional when seen through red-blue glasses.
This conical pile of soil is about 10 centimeters (4 inches) tall. The
sources of material that the robotic arm has dropped onto the Caterpillar
pile have included the "Dodo" and ""Upper Cupboard" trenches and, more
recently, the deeper "Stone Soup" trench.
Observations of the pile provide information, such as the slope of the
cone and the textures of the soil, that helps scientists understand
properties of material excavated from the trenches.
For the Stone Soup trench in particular, which is about 18 centimeters (7
inches) deep, the bottom of the trench is in shadow and more difficult to
observe than other trenches that Phoenix has dug. The Phoenix team
obtained spectral clues about the composition of material from the bottom
of Stone Soup by photographing Caterpillar through 15 different filters of
the Surface Stereo Imager when the pile was covered in freshly excavated
material from the trench.
The spectral observation did not produce any sign of water-ice, just
typical soil for the site. However, the bigger clumps do show a platy
texture that could be consistent with elevated concentration of salts in
the soil from deep in Stone Soup. The team chose that location as the
source for a soil sample to be analyzed in the lander's wet chemistry
laboratory, which can identify soluble salts in the soil.
The Phoenix Mission is led by the University of Arizona, Tucson, on behalf
of NASA. Project management of the mission is by NASA's Jet Propulsion
Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin
Space Systems, Denver.
