From Popular Mechanics
In 2018, planetary scientist Roberto Orosei and his colleagues stirred up a multi-planetary controversy when they claimed they’d found evidence of a subglacial lake nearly a mile below ice at Mars’s south pole. At the time, fellow planetary scientists met the claims with intense scrutiny.
Now, Orosei, a planetary scientist at Italy’s National Institute for Astrophysics, and his fellow researchers say they have new, additional evidence that these deep, vast subglacial lakes really do exist. They published their findings this week in the journal Nature Astronomy.
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If these lakes are, in fact, real, they could reshape our understanding of whether life could still exist on Mars. “This area is the closest thing to ‘habitable’ on Mars that has been found so far,” Orosei told Science News.
The Key Ingredient: Salt
Scientists believe Mars was covered in a vast network of liquid water seas roughly 4 billion years ago. Now, the planet is a dusty, desolate wasteland. But some of that water is still on Mars’s surface in the form of ice tucked along steep crater walls at the planet’s poles. Because the surface of Mars is so cold—and because atmospheric pressure is so low—liquid water can’t exist on its surface.
The secret ingredient in keeping Martian water liquid below the surface, researchers believe, could be salt. Because salt lowers the freezing temperature of water, it’s more likely that any liquid water below the Red Planet’s surface would have a nice brine to it.
“If the bright material really is liquid water, I think it’s more likely to represent some sort of slush or sludge,” planetary geophysicist Mike Sori, of Purdue University, told Nature. There’s a chance that nearby source of geothermal energy could also be warming up the water.
In total, the latest observations revealed three new possible bodies of water in addition to the one previously spotted in 2018. The largest of the buried lakes, the European Space Agency (ESA) reports, can be found along Mars’s southern pole and measures roughly 12 by 18 miles. Based on the data, it also appears to be surrounded by a cluster of three small ponds.
So what does this mean for the search for evidence of life on Mars? Salty environments are notoriously difficult for microbial life, but some extremophiles have found a way to live in similar habitats on Earth. For example, in 2016, researchers discovered thriving colonies of microbes along the salt-encrusted edges of Mono Lake in California.
Analyzing Old Data
Orosei and his team analyzed data from the ESA’s Mars Express probe, which has orbited Mars since 2o03.
The orbiter’s MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument, which keyed researchers in on the 2018 discovery, shoots radio waves at Mars’s surface in order to find pockets of liquid amid deposits of harder materials like rock and ice.
Radar signatures reflected from liquid are different—in this case, showing up as a bright white smudge—from surrounding rock and ice. (This is the same technique that has helped scientists find water beneath large glaciers here on Earth.)
Orosei and his team studied 134 observations collected by MARSIS between 2012 and 2019. (One of the reasons the 2018 findings were so controversial is that the team relied on only 29 MARSIS observations gathered between 2012 and 2015.)
Still, more research is needed. Fortunately, three missions are headed for the Red Planet. China’s Tiawen-1 mission, for example, has an orbiter equipped with radar instruments that could help pinpoint whether liquid water really is churning below Mars’s surface.
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