A Dynamic Spirit Site

5 January 2004
Two Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images acquired before the spectacular January 2004 landing of the Mars Exploration Rover (MER-A), Spirit, show the area where the lander is currently believed to have touched down. The identification of the area shown in the two pictures above is based on the pictures acquired by Spirit's descent imaging system just before landing. The lower picture was obtained by MGS MOC on 22 July 2003, the upper picture was acquired less than a month ago on 10 December 2003. What is exciting about these two pictures is the differences in the patterns of dark, squiggly streaks. These streaks are believed to have been caused by the removal of bright dust by large, passing dust devils. Comparison of the picture from July 2003 with that of December 2003 show that a different dark streak pattern developed over a period of less than 5 months.

These two MOC images suggest that the landing site is a dynamic, changing place on the time scale of several months. MGS MOC has never seen a dust devil occur in Gusev Crater, the location of the Spirit landing site. MGS always flies over Gusev around 2 p.m. local time, so this means that dust devils are not believed to be common around 2 p.m. However, the changes in the dark streaks suggest that dust devils definitely have occurred in Gusev Crater over the past 5 to 6 months, and they most likely occur earlier than 2 p.m. (perhaps closer to local 1 p.m. or noon).

These two MOC images are simple cylindrical map projections (rotated somewhat; note the north arrow, N) at a scale of about 3 meters per pixel (~10 ft/pixel); the 300 meter scale bar is about two-tenths of a mile long. The images are located near 14.7°S, 184.6°W, and are illuminated from the left.