Annotated Version
This map shows the thickness of the south polar layered deposits of Mars,
an ice-rich geologic unit that was probed by the Mars Advanced Radar for
Subsurface and Ionospheric Sounding (MARSIS). The MARSIS radar is an
instrument on the European Space Agency's Mars Express orbiter. The
thickness of the layered deposits was determined by measuring the time
delay between radar echoes from the surface and those from the lower
boundary, or "bed," of the deposits. The radar data indicate that the
deposit, larger than Texas in area, is more than 3.7 kilometers (2.3
miles) thick in places, and that the material consists of nearly pure
water ice with only a small component of dust.
The map was generated by comparing the elevation of the bed as determined
by MARSIS with the high-resolution map of surface topography obtained by
the Mars Orbiter Laser Altimeter aboard NASA's Mars Global Surveyor
orbiter. The thickness of the layered deposits is shown by colors, with
purple representing the thinnest areas, and red the thickest. The total
volume of ice in the layered deposits is equivalent to a water layer 11
meters (36 feet) deep, if spread evenly across the planet. The boundary of
the layered deposits was mapped by scientists from the U.S. Geological
Survey. The dark circle in the upper center is the area poleward of 87
degrees south latitude, where MARSIS data cannot be collected. The map
covers an area 1,670 by 1,800 kilometers (1,035 by 1,115 miles).
MARSIS is an instrument on the European Space Agency's Mars Express
orbiter. NASA and the Italian Space Agency jointly funded the instrument.
The Mars Orbiter Laser Altimeter flew on NASA's Mars Global Surveyor
orbiter.
