Contemporary Water and Habitability of Mars
When: November 3, 2017 9AM PDT
Mars is the only other planet besides Earth with multiple lines of geomorphic and spectral evidence for the past existence of flowing water on the surface. In the current climate, water on Mars exists almost entirely in the form of ice and in minor form as a gas. The notion of contemporary liquid water on Mars has been controversial. Pure liquid water on the surface would be rapidly lost to the tenuous atmosphere of Mars via evaporation; however, brines can be stable on the Martian surface for an extended period due to their lower eutectic temperature and evaporation rate. One of the major Mars discoveries of recent years is the existence of recurring slope lineae (RSL), which suggests that liquid water may occur on or near the surface of Mars today.
Recently, hydrated oxychlorine salts, including perchlorates, were spectrally detected at sites hosting RSL which implicates that water does play a role in the formation of RSL, although the magnitude of the role is uncertain. If RSL are indeed contemporary brines on Mars, they might provide transiently wet conditions near the surface on Mars, although the water activity in oxychlorine-salt solutions may be too low to support known terrestrial life. Widespread perchlorates may also challenge our ability to characterize some organic species via traditional pyrolysis experiments on Mars because of their reactivity with organics. Further astrobiological characterization and exploration of these unique regions on Mars are necessary to fully assess the current habitability of Mars.