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Laser Altimeter Provides First Measurements of Seasonal Snow Depth on Mars
A global view of how Mars changes with the seasons has been provided by extremely precise observations from two investigations on NASA's Mars Global Surveyor (MGS) spacecraft. Elevation and gravity measurements of Mars from MGS have been used to measure seasonal changes in the thickness of seasonal frost deposits and to provide the first direct measurement of their density. The observations were obtained from the Mars Orbiter Laser Altimeter (MOLA) and the spacecraft's radio tracking system. Over the course of a Martian year, which consists of 687 Earth days, as much as a third of Mars' tenuous carbon dioxide (CO2) atmosphere "freezes out" during the winter in the northern and southern hemispheres. A team consisting of Dr. David E. Smith of Goddard and Drs. Maria T. Zuber and Gregory A. Neumann of the Massachusetts Institute of Technology, measured changes in the height of the Martian surface every two weeks. They showed that small changes in surface height correlate with the expected times of deposition and evaporation of CO2 from the surface. The group also measured miniscule changes in the gravity field of Mars due to the movement of carbon dioxide, which allowed them to make the first measurement of the density of surface frost deposits. "Snow on Mars is composed of dry ice and last year it reached a maximum depth of 1.5 to 2 meters near both the north and south poles," explained Smith, Principal Investigator of the laser altimeter investigation and lead author of the study published in the December 7 issue of Science. For more on
the snow depth research on Mars, go to:
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