Author: Lisa Grossman / Source: Science News
The search for life on Mars just got a lot more interesting.
For decades, scientists have looked at the dry and dusty planet and focused on finding regions where life could have taken root billions of years ago, when the Martian climate was warmer and wetter.
But on July 25, researchers announced they had spotted signs of a large lake of liquid water hiding beneath thick layers of ice near the Red Planet’s south pole (SN Online: 7/26/18).If the lake’s existence is confirmed, we could find microbes living on Mars today.
That report changes the calculus for astrobiologists who want to protect any existing extraterrestrial life from being wiped out or obscured by introduced species from Earth (SN: 1/20/18, p. 22). Mars landers and rovers are cleaned to strict standards to avoid any possible contamination, even “without having anything you’d even call a pond,” says astrobiologist Lisa Pratt, NASA’s planetary protection officer. “Now we have a report of a possible subglacial lake! That’s a major change in the kind of environment we’re trying to protect.”
So how does finding the lake change the quest for life on Mars?
First things first: Could anything actually live in this lake?
It would be a tough territory for most Earthly microbes. Life on Earth fills every niche it can find, from cave crystals to arid deserts (SN: 3/31/18, p. 14). But the low temperature cutoff for most terrestrial life is around –40° Celsius. The Martian ice sheet is about –68° C.
“It’s very cold, colder than any environment on Earth where we believe life can either metabolize or replicate,” Pratt says.The lake does seem to contain plenty of water. But for the water to be liquid at such cold temperatures, it must be extremely salty. “On Earth, these kinds of briny mixtures present significant challenges to living organisms,” says planetary scientist Jim Bell of Arizona State University in Tempe, president of the Planetary Society….
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