Water may be forming in the soil near the Mars’ equator at night, though some of the liquid evaporates just after sunrise. Based on data from the Curiosity rover and published in Nature Geoscience this week, an active exchange of water is happening between the atmosphere and the surface of Mars. However, the conditions are too cold for the possibility of microbes.
While traversing Gale Crater near the Mars equator, the Curiosity rover has been taking measurements with its Rover Environmental Monitoring Station. Now, a large international team led by Javier Martín-Torres from Luleå University of Technology has analyzed a full Martian year’s worth of data on atmospheric humidity and temperature. While they can’t detect the liquid brines directly, “what we see are the conditions for the formation of brines on the surface,” Martin-Torres said.
Perchlorate is a type of salt that lowers the freezing temperature of water; it also pulls water molecules from the atmosphere to form a corrosive liquid brine. “These perchlorate salts have a property called deliquescence,” Martin-Torres adds. “They take the water vapor from the atmosphere and absorb it to produce the brines.” According to these new measurements, liquid brines could be forming in the uppermost soils of the crater during the Martian night, and then they’d evaporate as the ground and air begin to warm up after sunrise. Here’s a schematic of this hypothetical day-and-night water cycle:
Relative humidity depends on the temperature of the air and the amount of water vapor in it, and Curiosity’s measurements have ranged from 5 percent during summer afternoons to 100 percent in the nighttime during fall and winter. Pores in the soil interact with air just above the ground, and when the relative humidity gets above a certain level, the salts absorb enough water molecules to become dissolved in liquid. The subsurface water content estimated using Curiosity data is consistent with the existence of water molecules absorbed by perchlorates in soils.
However, the researchers found that the ground temperature in Gale Crater is too low to support terrestrial microorganisms and life as we know it.