Wind shadow and real shadow combine with an impact crater to produce a "comet." Winds blowing over the crater's rim have scoured the ground behind the crater free of light-colored dust, leaving exposed a relatively bare lava flow. The crater spans a width of about 3 kilometers (2 miles).
Humanity is a very visual species. We rely on our eyes to tell us what is going on in the world around us. Put any image in front of a person and that person will examine the picture looking for anything familiar. Even if the examiner has no idea what he/she is looking at in a picture, he/she will still be able to make a statement about the picture, usually preceded by the words "it looks like..." The image above is part of the surface of Mars, but is presented for its artistic value rather than its scientific value. When first viewed, this image solicited a statement that "it looks like..." something seen in everyday life.
Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.
NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.