Double, double, toil and trouble...
In the search for signs of Martian life, researchers have turned their attention to odd, funnel-shaped depressions on the Red Planet’s surface. The geological formations closely resemble the so-called “ice cauldrons” found on Earth’s tundras, say scientists from the University of Texas at Austin. These cauldrons, which form when volcanoes erupt under ice sheets, can brew a type of primordial soup that's excellent for nourishing microbial life.
“We were drawn to this site because it looked like it could host some of the key ingredients for habitability – water, heat and nutrients,” lead author Joseph Levy, a research associate at the University of Texas Institute for Geophysics, said in a statement.
Earlier this month, Dr. Levy and colleagues described two such depressions – one in the planet’s Hellas basin and another in the Galaxias Fossae region – in Icarus, the International Journal of Solar System Studies. Upon examining photos taken by NASA’s Mars Reconnaissance Orbiter, they noticed crack-like features along the depressions, similar to those seen on ice cauldrons in Iceland and Greenland.
“These features do really resemble ice cauldrons known from Earth, and just from that perspective they should be of great interest,” said Gro Pedersen, a volcanologist at the University of Iceland who was not involved with the study, in a statement. “Both because their existence may provide information on the properties of subsurface material – the potential existence of ice – and because of the potential for revealing ice-volcano interactions.”
But the evidence for their formation is still ambiguous. Debris surrounding the Galaxias Fossae depression may suggest an impact, rather than a volcanic event. But the Hellas depression lacks evidence for a surrounding ejecta blanket, researchers say, and contains fracture patterns associated with ice removal.
If either or both of these depressions really are ice cauldrons, they could contain warm, liquid water and chemical nutrients, key ingredients in the formation of life. Future Mars missions, researchers say, should consider this possibility.
Looking for life's ingredients
For better or worse, Earth remains our only frame of reference for understanding the requirements of life and thus for studying the habitability of the Red Planet, and as far as we know, liquid water is a must.
So researchers were excited in 2015 when NASA’s Curiosity rover discovered an area with very high concentrations of the chemical silica (SiO2) on Mars. On our planet at least, those kinds of silica concentrations are typically formed by water flowing through bedrock and leaving quartz (silicon dioxide) behind.
NASA has also identified large amounts of the element manganese in Martian rock. Manganese is typically found in basalt, which makes up most of Mars’ barren surface, but only in trace amounts. To achieve the concentrations detected by Curiosity, say scientists, Martian basalt would have to be dissolved in oxygenated water. Analysts say the discovery could prove that the planet’s atmosphere was once full of oxygen.