The search for signs of ice deposits on Mars is a complex process. To advance in this matter, Mars Express uses its radar to probe the interior. He sends low-frequency radio pulses to the Red Planet and records the received back signals. The pulses are able to penetrate part of the material of the planetary crust, displaying data on the composition and density. By analyzing the degree of delay, you can determine the characteristic hidden under the surface of the material.
The picture shows the radar echoes from the Plateau of Meridian. This area is also being explored by the Opportunity rover. The bright white line is the Martian surface, and a weak and more diffuse feature just below the echo signals from the base of the layer of the buried material. The surface of the Meridian Plateau is rich in volcanic sands containing minerals created in the presence of water. It is unclear what materials lie below the surface, but the radar has found a similarity with ice.
However, a recent study showed that a dense layer of porous sand would also be suitable as an explanation. This data once again confirms the complexity of the search for hidden ice deposits. But it is important for researchers to identify these points, because ice will become an important resource for future colonists.
Radar received by the radar MARSIS in April 2016. The width of the territory covered is 80 km.