The Mars Reconnaissance Orbiter's spectrometer has found evidence of hydrates deposited by salty water associated with Recurring Slope Linae (RSL) on Mars.
RSL are more-or-less dark vertical lines that appear on crater and hillsides when Mars is relatively warm, above -10 F (-23 C) and disappear when temps are colder. The MRO's spectrometer shows hydrated salts at multiple locations when the dark lines are widest, and doesn't detect them when the RSL are less extensive.
The salts are a mixture of magnesium perchlorate, magnesium chlorate, and sodium perchlorate.
On Earth, perchlorates are found in deserts and have been shown to keep liquids from freezing down to as low as -94 F (-70C).
The thinking seems to be that salty ice under the surface melts as the Sun's heat heats the soil, and flows as a liquid through the sandy soil, some of it percolating to the surface, producing the dark markings.
http://phys.org/news/2015-09-evidence-brine-mars.html
RSL are more-or-less dark vertical lines that appear on crater and hillsides when Mars is relatively warm, above -10 F (-23 C) and disappear when temps are colder. The MRO's spectrometer shows hydrated salts at multiple locations when the dark lines are widest, and doesn't detect them when the RSL are less extensive.
The salts are a mixture of magnesium perchlorate, magnesium chlorate, and sodium perchlorate.
On Earth, perchlorates are found in deserts and have been shown to keep liquids from freezing down to as low as -94 F (-70C).
The thinking seems to be that salty ice under the surface melts as the Sun's heat heats the soil, and flows as a liquid through the sandy soil, some of it percolating to the surface, producing the dark markings.
http://phys.org/news/2015-09-evidence-brine-mars.html