MARSIS sending signals and receiving echoes

The principle of radar science used by MARSIS is based on the detection of radio waves reflected by boundaries between different materials. By analysis of these echoes, it is possible to deduce information about the kind of material causing the reflection, such as estimates of its composition and physical state.

Different materials are characterised by their ‘dielectric constant’, that is the specific way they interact with electromagnetic radiation, such as radio waves. When a radio wave crosses the boundary of different layers of material, an echo is generated and carries a sort of fingerprint from the specific materials. The MARSIS antenna booms here are seen receiving reflected signals. The red dotted line denotes the top of the ionosphere of Mars.