Liquid water collects in the Martian soil each night, before evaporating during the day, according to NASA’s Curiosity rover. If future missions can confirm this water cycle, it means astronauts could one day farm moisture to provide drinking water on Mars.
Planetary scientists have seen a lot of evidence for frozen water at the Martian poles, and water vapour in the planet’s atmosphere. Liquid water, on the other hand, has been harder to come by, as the temperature and atmospheric pressure at the surface is too low.
perchlorate salts in the planet’s soil are lowering the freezing temperature of water, setting up conditions for liquid brines to form at equatorial regions, new research from NASA’s Curiosity rover shows. Findings, published in this week’s Nature Geoscience, are based on nearly two years worth of atmospheric humidity and temperature measurements collected by the roving science laboratory Curiosity, which is exploring an ancient impact basin called Gale Crater near the planet’s equator.
The brines, computer models show, form nightly in the upper 2 inches of the planet’s soil as perchlorates absorb atmospheric water vapor. As temperatures rise in the morning, the liquid evaporate
The brines, computer models show, form nightly in the upper 2 inches of the planet’s soil as perchlorates absorb atmospheric water vapor. As temperatures rise in the morning, the liquid evaporates.
The levels of liquid, however, are too low to support terrestrial-type organisms, the researchers conclude.
The team found that during Martian winter, conditions throughout the cold but humid nights would allow liquid water to be stable in the first 5 centimetres of the surface. Shorter periods of stability would also be possible in other seasons.
They suggest that calcium perchlorate in the ground absorbs water from the atmosphere until it dissolves into a salty solution, or brine. This process is called deliquescence. When the sun comes up and the temperature rises, the water evaporates and returns to the atmosphere, starting the cycle anew.
Curiosity can’t measure this water directly, says Martin-Torres, but everything is in place for it to be there. “We find the conditions for brines to be produced, but if you want to measure them directly you need some other kind of measurement,” he says, such as an instrument that can look for changes in electrical conductivity.
If the water is there, it’s unlikely to harbour life, as the temperature is below -30 °C on average – too cold for even extreme Earth microbes to replicate and metabolise. “The fact that no microorganisms on Earth can grow at temperatures lower than -20 °C or so suggests that this could be a hard limit for water-based life,” says Davila.
This water might one day help life flourish on Mars in other ways, however. Martin-Torres is currently working on a proposed device for the European Space Agency’s ExoMars rover, due to launch in 2018, that would exploit Curiosity’s findings. “It’s a proof of concept of an instrument that will take water out of the atmosphere to produce liquid water for astronauts,” he says. Small containers holding salts and mounted on the rover would mimic the natural deliquescence process. If it works, future astronauts could do the same on a larger scale to support Mars exploration.
SOURCES – New Scientist, Nature Geoscience, Discovery News