科学美国人60秒:Martian Soil Salts May Make Water Ice All Wet

If Martians exist, even the microbial sort, they probably need liquid water. Temperatures on the surface of the red planet are below freezing, but signs exist that water flowed in the past—and perhaps still does, thanks to a Martian version of anti-freeze.
 
Salts lower the freezing point of water, as anyone knows who’s thrown salt on an icy sidewalk. And both NASA’s Phoenix and Curiosity missions found salts called perchlorates sprinkled around the Martian surface.
 
To see how perchlorates might act on Mars, researchers recreated the pressure, humidity and temperature of the planet inside a metal cylinder. They put a thin layer of perchlorates on top of water ice inside the chamber. Within minutes, droplets of liquid water formed, even at minus 100 degrees Fahrenheit.

Some scientists thought perchlorates might condense water vapor from the atmosphere. But within the cylinder, no liquid water formed in the presence of salts, either alone or on Mars-like soil, unless ice was present too. The study is in the journal Geophysical Research Letters. [Erik Fischer et al, Experimental evidence for the formation of liquid saline water on Mars]

The finding study could explain mysterious globules seen on the leg of the Phoenix in 2008. The lander may have been dotted with drops of otherworldly water.

—Clara Moskowitz
                                                                                                 
(The above text is a transcript of this podcast)