16/03/2007 2:52 pm
NASA/JPL/ASI/ESA/Univ. of Rome/MOLA Science Team
The upper image of this composite is a ‘radargram’ from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board ESA’s Mars Express. It shows data from the subsurface of Mars in the ice-rich layered deposits that surround the south pole.
The lower image shows the position of ground track of the spacecraft (indicated by a white line) on a topographic map of the area based on data from the MOLA laser altimeter on board NASA's Mars Global Surveyor. The images are 1580 kilometers wide. A non-annotated version of the image can be found here.
The MARSIS radar 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 kilometres of ice. The total elevation difference shown in the topographic map is about 3 kilometres between the lowest surface (dark blue) and the highest (yellow).
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