NASA's Phoenix Mars Lander's Robotic Arm Camera took this image on Sol 71 (August 6, 2008), the 71st Martian day after landing. The shadow shows the outline of Phoenix's Thermal and Electrical Conductivity Probe, or TECP. The holes seen in the Martian surface were made by this instrument to measure the regolith's conductivity. A fork-like probe inserted into the soil checks how well heat and electricity move through the dirt from one prong to another. Credit: NASA/JPL-Caltech/University of Arizona/Max Planck Institute
