Astronomy Picture of the Day—20180801

Discoverthe cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2018July 31

Layersof the South Pole of Mars

ImageCredit & License: ESA/DLR/FU Berlin; Bill Dunford

Explanation:What lies beneath the layered south pole of Mars? A recent measurement withground-penetrating radar from ESA's Mars Express satellite has detected abright reflection layer consistent with an underground lake of salty water. There flection comes from about 1.5-km down but covers an area 200-km across.Liquid water evaporates quickly from the surface of Mars, but a briny confined lake, such as implied by the radar reflection, could last much longer and be acandidate to host life such as microbes. Pictured, an infrared, green, and blueimage of the south pole of Mars taken by Mars Express in 2012 shows a complex mixture of layers of dirt, frozen carbon dioxide, and frozen water.