The question of whether or not life could/can survive on Mars was brought to the forefront of popular media this month with NASA’s announcement of water currently flowing on Mars, Matt Damon “science-ing the sh!t out” of the red planet in the Hollywood release of The Martian, and Google’s adorable doodle of Mars drinking a large gulp of water. Together, these events have led to an increased interest in the habitability of Mars and, in the spirit of the “Week of Mars”, I’ve decided to talk about the habitability of Mars as well!
The most recent evidence for water flowing on Mars came from a publication by Ohja et al. (2015) in Nature Geosciences that examined the mineralogic composition of long, low-reflectance features known as recurring slope lineae (RSL) on the surface of Mars. Notably, RSL on the surface of Mars is not a new observation but Ohja et al. (2015) presented the first evidence of hydrated salts in locations where RSL are present. These salts were observed at times when RSL activity was the highest and suggest that water, although briny, is forming on seasonally warm slopes of contemporary Mars!
On Earth, systems such as the Atacama desert (annual rainfall of <1 mm/yr) provide a window as to how life might survive on a hyperarid, salty planet. In the Atacama, salt deliquescence, or the absorption of water vapor on salt minerals, can sustain microbial communities of cyanobacteria and heterotrophs living within rocks. These findings suggest that if an organisms is capable of withstanding the other extremes of the Martian surface (radiation, high concentrations of salt, etc) the seasonal RSL may provide enough water to sustain life similar to that of our planet–although this is still uncertain.
And what about us? Well, <Spoiler Alert> “The Martian” showed us that plants can grow on Martian soil which seems to be within reach of our gardening capabilities and might even be possible without the addition of a human fertilizer. 😉 Another problem faced by “The Martian” was how to generate enough water to sustain his crops. Unfortunately, the new observation of hydrated salts occurring in RSL does not necessarily mean we’ll be able to easily collect water on the surface. The main problem is that the observed RSL are thought to be formed by deliquescence of perchlorate salts, the same process happening in the Atacama desert, and would, most probably, not provide enough water to sustain a colony of Martian explorers. Frozen water in the subsurface of Mars, however, has been well established and may offer an alternative for collecting and sustaining a Martian colony yet accessing and purifying the water may be costly.
Either way, there is still a lot to learn about the red planet. I hope last week got you excited about Mars and the exploration for life on other planets!