Radar sounder instruments orbiting Mars have looked beneath the Martian
surface and opened up the third dimension for planetary exploration. The
technique's success is prompting scientists to think of all the other
places in the Solar System where they would like to use radar sounders.
The first radar sounder at Mars was the Mars Advanced Radar for Subsurface
and Ionospheric Sounding (MARSIS) on the European Space Agency's Mars
Express Orbiter. It has been joined by the complementary Shallow
Subsurface Radar (SHARAD), operating at a different wavelength aboard
NASA's Mars Reconnaissance Orbiter. The data in this animation are from
SHARAD.
