A new million-dollar NASA project led by the University of Michigan aims to discover whether drops of salt water are common on Mars - and whether microbial life could survive in them.
Three years ago, beads of liquid brine were photographed on one of the Mars Phoenix lander's legs. And, says UM professor Nilton Renno, "On Earth, everywhere there's liquid water, there is microbial life."
The scientists plan to create Mars conditions in lab chambers and study how and when brines form. The modules will have the same wispy carbon dioxide and water vapor atmosphere as Mars,with 99 percent lower air pressure than Earth's sea level average.
Temperatures will range from -100 to -80 Fahrenheit and will be adjusted to mimic daily and seasonal cycles. Instruments will monitor the chambers for the formation of brine pockets, which could potentially be habitable by certain forms of microbial life.
Meanwhile, colleagues will seed similar chambers with salt-loving 'extremophile' microorganisms from the depths of Antarctic lakes and the Gulf of Mexico. The aim is to discover whether these organisms can survive, grow and reproduce in brines just below the surface of the soil.
All known forms of life need liquid water to live. But microbes don't need much, says the team - a droplet or a thin film could be enough.
"If we find microbes that can survive and replicate in brines at Mars conditions, we would have demonstrated that microbes could exist on Mars today," says Renno.
The Phoenix photos are believed to be the first pictures of liquid water outside the Earth. Independent physical and thermodynamic evidence as well as follow-up experiments have confirmed that the drops were liquid and not frost or ice.
The median temperature at the Phoenix landing site was -70 degrees Fahrenheit during the mission - too cold for liquid fresh water. But perchlorate salts found in the site's soil could lower the water's freezing point dramatically, so that it could exist as liquid brine. The salts are also capable of absorbing water from the atmosphere.
There's evidence that brine was once abundant on Mars, and recent images have indicated that it may still be flowing.