Using the Shallow Radar instrument aboard NASA's Mars Reconnaissance Orbiter, Holt was able to peek beneath the ice's surface for clues; in particular, the radar could pick out differences in electrical reflectivity between overlying layers, showing how the ice built up over time. (discovermagazine.com)
Suspect Lake Shape To explain the lower chaotic deposits, we can imagine a cosmic body hitting soggy ground overlying a layer of permafrost several tens of meters thick. (scientificamerican.com)