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The search for life on Mars has become much more interesting.
For decades, scientists have examined the dry, dusty planet and focused on areas where life could have taken root billions of years ago. the climate was warmer and wetter. But on July 25, researchers announced they spotted signs of a large lake of liquid water hidden under thick layers of ice near the south pole of the red planet ( SN Online : 26/07/18 ). If the existence of the lake is confirmed, we could find living microbes on Mars today.
This report changes the calculation for astrobiologists who want to protect any existing extraterrestrial life from being erased or obscured by introduced species from the Earth ( SN: 1/20/18, page 22 ). The undercarriages and rovers of Mars are cleaned to strict standards to prevent any possible contamination, even 'without a so-called pond,' says astrobiologist Lisa Pratt, head of the planetary protection of NASA. "Now we have a report of a possible subglacial lake! It's a major shift in the kind of environment we're trying to protect."
So, how to find the lake change the quest for life on Mars?
First, could anything live in this lake? 19659007] This would be a difficult territory for most terrestrial microbes. Life on Earth fills every niche it can find, from cave crystals to arid deserts (SN: 31/03/18, p. 14) . But the low temperature threshold for most land activities is about -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 be metabolized or replicated," says Pratt
. But for the water to be liquid at such cold temperatures, it must be extremely salty. "On Earth, these types of brine mixes pose significant challenges to living organisms," says global scientist Jim Bell of Arizona State University in Tempe, chairman of the Planetary Society. "Even extremophile bacteria that can live in very salty water may not be able to survive."
But could Martians live there? "19659007" Absolutely, "he says.His friendly past, some organisms could have adapted to climate change and ended up finding the cold and salt water quite comfortable, she said. For me, this sounds like an ideal hideaway, a place where one could just wait, wait for the surface conditions to improve. "
What's Different in this lake compared to other aquatic places where we hope to find life, like the moon Enceladus of Saturn?
For planetary explorers, Mars has a major advantage over the frozen moons of Saturn and Jupiter: we have Landing to Mars is a relatively fast journey of about four to eleven months, and the atmosphere of the planet makes landing much simpler than on the tiny moons without air. [19659002] The big question for planetary protection is whether Lake Mars surfaced On Saturn's moon Enceladus and perhaps on Europa's moon of Jupiter, liquid water from an underground ocean squirts into space from cracks in the ice ( SN: 6/9/18, p.11 ). These plumes could make ocean sampling relatively simple: a spaceship could just catch a little spray during a flyby. But the fact that water can escape means that invading microbes can enter it.
Even though no Mars spacecraft has landed near the lake, global dust storms – like the one that rages on Mars – could be contaminated from anywhere on the planet. ( SN Online: 13/06/18 )
"So, if [the lake is] is real, let's hope that there will be no passage in the interior "said Pratt.
If there is no way to get in or out, how can we see if something is alive there?
To check the lake for signs of life, "you have to drill," says planetary scientist Isaac Smith of the Planetary Science Institute, based in Lakewood, Colorado. It's as well as scientists have probed lakes Subglacial similar on Earth, such as Lake Vostok in Antarctica, in which Russian scientists dug in 2012 ( SN: 11/7/13, p.26 ). This team stated that the lake was home to a thriving ecosystem, although researchers later admitted that the samples were contaminated with drilling fluid.
The drilling on Mars would be even more difficult technically and could meet the opposition of the scientific community. Russian team did. "Like the subglacial lakes of Antarctica, [the Mars lake] would be considered an extraordinarily rare and special place," says Pratt. "I'm waiting for there to be a lot of resistance to drilling in."
But if we are lucky, there could be a sign from above. Signs of seasonal variations in methane in the Martian atmosphere have piqued the interest of astrobiologists as a possible sign of microbial life beneath the surface ( SN: 7/7/18, p.8 ). ExoMars Trace Gas Orbiter of the European Space Agency, which began collecting data in April, is looking for more methane
"ExoMars could find a smoking gun, so to speak," says global scientist Roberto Orosei of National Institute of Astrophysics. Bologna, Italy, who was part of the team who discovered the lake. "The association of liquid water and methane in the atmosphere would be very, very exciting proof of something happening on Mars."
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