The "Thickness" of Mars' South Polar Layered Deposits (Map 1)

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 Km (about 2,3 miles) thick in places, and that the material consists of nearly pure water ice with only a small component of dust.