There’s a whole cadre of scientists who spend long periods of time in Earth’s most inhospitable environments, specifically looking for life where there probably shouldn’t be any. Years are spent drilling miles-deep holes into ice cover in Antarctica, collecting salty desert water samples, and analyzing heretofore unknown microbial processes so that we can know the many bizarre ways life manages to keep on keeping on.
If life can survive in the prehistoric waters of a frozen Antarctic lake, perhaps it can survive on moons like Europa or Enceladus or some other extreme environment in the solar system. Perhaps it can survive in salty flowing water on Mars.
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With Monday’s announcement that Mars likely has seasonal liquid water flows, it seems like the day when an extremophile researcher has the chance to study an extraterrestrial ecosystem (if we can call it that) is an inevitability rather than a pipe dream.
The discovery raises the obvious question: Is there life in the Palikir Crater’s flowing water? The obvious answer right now is, “we don’t know,” but thanks to the work of these extremophile biologists, we can at least make some educated guesses as to whether known types of life might be able to handle the ecosystem.
“It’s probably at the upper limits of what we know on Earth”
Almost invariably, these biologists are looking at ways that an Earth environment might mimic one on another planet—now we’ll get the chance to see whether an environment on another planet is similar to one we’ve seen on Earth.
The fact that we’re able to see the physical streaks that salt brine leaves on the Martian surface suggest that the water’s salinity content is quite high.
“It looks to be a very salty brine—as for how salty that is, it’s probably at the upper limits of what we know on Earth,” Mikki Osterloo, a geologist at the University of Colorado Boulder who is an expert in Martian saline environments told me. “For life to have evolved in such a very high brine is potentially difficult to do, but I’m not going to say it’s impossible.”
That’s because we’ve seen similar chlorite streaks in Antarctica and in Chile’s Atacama desert—both places we’ve found life surviving against the odds.
In 2012, researchers at the Desert Research Institute in Nevada described not one, but 32 different species of bacteria living in Antarctica’s Lake Vida. Not only is that lake impossibly cold—it’s covered in a 30-foot layer of ice—it’s also six times saltier than sea water, which is why temperatures dip down to 8.6 degrees Fahrenheit.
“It has expanded our view of the types of ecosystems that are habitable,” Alison Murray, lead researcher on that study, told me soon after the discovery. “It’s a pretty diverse community.”
“We’ve seen some very high salinity brines in the Atacama and in Antarctica”
Also in 2012, scientists described an “oasis” of microorganisms living without sunlight or oxygen, in hypersaline substrates two meters under the Atacama Desert. Not necessarily relevant to Mars, but extremophiles have been found just about everywhere scientists have looked.
Just because life thrives in those two ecosystems doesn’t mean the same is true for Mars. For one, we have no idea just how salty Mars’s water is, and we’re obviously not sure if there’s any sort of life anywhere on Mars, both of which are reasons to go check it out with a rover or perhaps an astronaut.
“The best way to figure out the salinity would be to go there,” Osterloo said, adding that it may be possible to make some ballpark estimates by observing different salt formations then attempting to recreate them in a laboratory on Earth. “We may be able to tie that back by doing Earth analogs. We’ve seen some very high salinity brines in the Atacama and in Antarctica.”
Osterloo told me she’s a “salt expert” and not an extremophile biologist, but said from what we know about Mars’s geological history and about extremophiles on Earth, it’s possible to guess how life might have survived there. Mars’s water hasn’t always been quite so salty, she said.
“Certain microbes can evolve to create a protective sheath that protects them against higher and higher salinity brines,” she said. “It’s possible that life evolved at a time when it wasn’t as saline but evolved to handle it as the water became saltier.”
