Liquid Water From Ice and Salt on Mars
Astrobiologists supported by the Exobiology and Evolutionary Biology element of the NASA Astrobiology Program have discovered that a salt on Mars could cause liquid water to form when it comes into contact with water ice. The study was inspired by images from NASA’s Phoenix mission, which showed what appeared to be droplets of liquid water on a leg of the lander.
Researchers determined that liquid water could be stable on Mars if it was very salty – a possibility that arose when calcium perchlorate was identified on the martian surface by missions including Phoenix and the Curiosity rover.
The team found that a particular type of salt found on Mars can actually melt ice that it touches. In tests where calcium perchlorate (or a salty, simulated mars soil) was placed on top of water ice, droplets of liquid water formed within minutes at temperature ranges within the conditions of the Phoenix landing site. The presence of water was confirmed by shining lasers on the surface and examining the reflected light in a process known as Raman scattering spectroscopy.
“For me, the most exciting thing is that I can now understand how the droplets formed on the Phoenix leg,” said Nilton Renno of the University of Michigan at Ann Arbor in a release issued by the American Geophysical Union.
On Earth, organisms known as halophiles are capable of surviving in water with extremely high concentrations of salt (e.g. hypersaline environments). Halophiles have been found thriving at a range of salinities – from 3% to 30% sodium (NaCl) – and in environments from Antarctica to the Arctic. Astrobiologists study halophiles and the mechanisms they use to survive in order to determine environmental boundaries in which life survives on Earth.
The new study indicates that liquid droplets of water could form on Mars wherever perchlorate comes into contact with water ice, opening up the possibility that environments for life could persist all over the planet. The question now: could droplets of salt water help halophiles similar those on Earth survive within the environmental boundaries on Mars?
The study, “Experimental evidence for the formation of liquid saline water on Mars,” was published in the journal Geophysical Research Letters.