The story of water in our solar system is ever-changing, and the story of water on Mars, in particular, seems to get more confusing with every new paper.

Earlier this week, we brought you news of a January 24 paper in Geophysical Research Letters that explained why Mars probably doesn’t have water under its south polar glaciers, even though bright radar returns are seen. According to that paper, led by Cyril Grima, bright radar returns from under Mars’s south polar ice cap are from lava rock and not water.

Yesterday, January 26, we got early access to a paper that will be published on February 1 in Earth and Planetary Science Letters describing lab experiments run to determine what kinds of salty waters and water-sediment configurations could exist under Mars’s south polar glaciers. As laboratory geophysicist David Stillman explains: The exotic salts that we know exist on Mars have amazing ‘antifreeze’ properties allowing brines to remain liquid down to -103 degrees Fahrenheit. We studied these salts in our lab to understand how they would respond to radar.

We are now in the position of having one research paper that says the bright radar returns that folks originally thought were water are almost definitely not water and another paper saying, “But if it is water, this is how it could exist.” And that is kind of neat. 

While it’s possible there could be lakes of deadly perchlorate or chloride brines, Stillman explains: These brines could exist between the grains of ice or sediments and are enough to exhibit a strong dielectric response. This is similar to how seawater saturates grains of sand at the shoreline or how flavoring permeates a slushie but at -103 degrees Fahrenheit below a mile of ice near the South Pole of Mars.

Good job, everyone. Can we please get a drilling rig on Mars? I think we may need to do some digging to understand exactly what is going on.

More Information

SwRI press release

“Assessing the role of clay and salts on the origin of MARSIS basal bright reflections,” Elisabetta Mattei et al., 2022 January 19, Earth and Planetary Science Letters