Geochemical and Astrobiological Studies on Martian Aqueous Solutions at Subzero Temperatures

Grant #: NNX10AB76A
Senior Scientist: afairen

Minerals expected to form in Martian past liquid water environments, commonly called "aqueous minerals”, include carbonates, phyllosilicates, sulfates and iron oxides. The long-term presence of water masses on Mars, needed to promote the synthesis of those mineral assemblages, is still undergoing vivid debate. Water on Mars has been explained by invoking controversial and mutually exclusive solutions based on warming the atmosphere with greenhouse gases (the “warm and wet” Mars) or on local thermal energy sources (the “cold and dry” Mars). Both have critical limitations and none has been definitively accepted as a compelling explanation for the presence of liquid water on Mars.

In this proposed investigation the PI will try to solve this conundrum, testing the hypothesis that cold, saline and acidic liquid solutions could have been stable on the surface of Mars under a mean temperature of roughly 250 K and for relatively extended periods of time, completing a hydrogeological cycle in a water-enriched but freezing planet, a “cold and wet” Mars. In this scenario, he will analyze: (1) the suite of aqueous minerals that precipitated as a consequence of the enduring stability of water on the surface; (2) the sequence and time of deposition of the different aqueous minerals which precipitated in the cold watery environments; and (3) the long-term remobilization and redistribution of salts downward into the subsurface during and after the transition to the cold and dry environment that Mars is today. The PI also aims to conduct a systematic search for extant and extinct life, and itsremains, in the aqueous minerals deposited by the cold hydrogeological cycle.

He will investigate:

(1) the possibilities for life in the past, testing the challenges that primeval life would have to overcome to thrive in the high ionic strength of the modeled aqueous solutions, particularly if the water activity permitted some kind of biology similar to that on Earth; and

(2) the chances for life on Mars today, analyzing the hygroscopicity of several terrestrial salts that have also been reported on Mars as remnant deposits of the primeval hydrological system, such as perchlorates and chlorides, and their capacity to host wet microenvironments now and in the past.

Finally, he will propose and test a novel methodology to search for life in some well known sediments reported as remnants of the ancient hydrogeological cycle on Mars, the sulfate deposits, examining the differences in the thermal behavior of two sets of terrestrial sulfate minerals with different origin: biogenic and abiogenic. Therefore, in this investigation, a differentiation will be made between the potential habitability of Mars whether in the past or now, and the actuality of life on Mars as expected to be revealed by a new search protocol.