The upper image is a radargram from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), showing data from the subsurface of Mars in the ice-rich layered deposits that surround the south pole. The lower image shows the position of the ground track (white line) on a topographic map of the area based on Mars Orbiter Laser Altimeter data. The images are 1,580 kilometers (980 miles) wide.
The MARSIS echo trace splits into two traces near the left edge of the image, at the point where the ground track crosses from the surrounding plains onto the elevated layered deposits. The upper trace is the echo from the surface of the deposits, while the lower trace is interpreted to be the boundary between the lower surface of the deposits and the underlying material. The strength of the lower echo suggests that the intervening material is nearly pure water ice. Near the image center, several bright bands between the echo traces are likely caused by interaction of the radar waves with internal layers of the deposits. The time delay between the upper and lower traces in the banded area is 20 microseconds, corresponding to a thickness of 1.6 kilometers (1.0 miles) of ice. The total elevation difference shown in the topographic map is about 3 kilometers (2.5 miles) between the lowest surface (dark blue) and the highest (yellow).
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.