Mars is home to a huge subterranean aquifer with liquid water, according to a group of scientists who have found meaningful evidence. The subterranean lake was not seen directly, but if it is real, it is a discovery that substantially increases the likelihood that the Red Planet could harbor life.
Researchers have discovered the potential reservoir with the Mars Express Orbiter orbiting Mars since 2003. When scanning the ice cap at the south pole of Mars, the radar instrument of the probe, called MARSIS, detected a feature about a mile below the surface, which was about 12.4 miles wide. The structure has a radar signature that matches that of buried liquid water here on Earth, leading the team to conclude that there is a lake under the glacier. The researchers say they have ruled out all other possibilities for what they see.
"I came up with the ideas of how to explain this in a way that is not water," says Roberto Orosei, researcher at Italy's National Institute of Astrophysics and head of the team that found the formation ] The Verge . "We tried to exploit every possible alternative, and we think we made it."
For For decades planetary scientists have been trying to find liquid water on Mars. most agree that it is likely in certain regions. This finding, detailed in Science today, is the first indication that water can exist in basins below the Martian surface. This has a huge impact on the search for extraterrestrial life on our Planet Neighbor: Bacteria were found here on Earth in the water under glaciers in Antarctica and Greenland. "Just about anywhere there is liquid water on Earth, you can find something that can survive in it," says Tanya Harrison, a planetary scientist and research director at Arizona State University's Space Technology and Science Initiative, who does not share in this discovery was involved The Verge . An underground reservoir could also be the perfect place to survive Mars microbes.
However, the idea of liquid water beneath the surface of Mars is certainly being discussed. Today's findings are based only on radar measurements, which means that it is difficult to confirm if we do not send more complex instruments to Mars in the future or if we actually drill into the ice. But if is a lake below the south pole of Mars, it may mean that there are more aquifers that we have not discovered yet. "This would be the first watering hole [on Mars] and the question arises: is that true and is there more of it?" Jim Green, NASA chief scientist, tells The Verge .
NASA is already pretty sure that some water will flow on the surface of the Red Planet. In 2015, the space agency announced that a bunch of bizarre dark streaks on Mars were probably saltwater. This was the first major affirmation that water exists as a liquid on Mars, which is remarkable given that the planet has an average temperature of -80 degrees Fahrenheit. Salt in the water lowers the freezing point and keeps it liquid in cold conditions; Scientists believe that the salt is probably from Marsteinen.
Some scientists have also doubted this strip. One team has suggested that the stripes are only dark grains of sand rolling downhill. But even if these streams are really liquid water, they are not quite habitable. They are quite small and thin and appear only during the warmer seasons, when it is possible that the water exists as a liquid. That said, winter would not be very hospitable. "Anywhere on the surface of Mars, even where water occurs periodically, a terrestrial living organism would die," says Orosei. "There are no conditions for their sustainable survival."
That's what makes this invisible aquifer so exciting: it's potentially big and stable. It's far enough underground for it to be unaffected by seasonal changes in the surface temperature of the planet, says Orosei. It probably contains many salts, such as magnesium, calcium and sodium. And the team believes that the polar ice on the water creates a strong pressure that also makes it easier for the reservoir to stay in a fluid state. Increased pressure prevents water from freezing at lower temperatures. So it is possible that this aquifer will remain liquid throughout the year, which is good news for habitability. "It's the closest to the habitat we found on Mars," says Orosei. "It is the only known place on Mars where a terrestrial micro-organism, at least the heaviest, could survive, although we do not know for sure."
Orosei and his team collected data from the South Pole in 2015 from May 2012 to December, and then spent another two years eliminating all sorts of alternatives to what the MARSIS instrument had measured , It is likely that other scientists are trying to find additional explanations. "The interpretation of this as water, I think many people in the community want to see more than just radar," said Cassie Stuurman, a research and development trainee at the satellite satellite agency Planet, who discovered a huge ice deposit under Mars in 2016 , tells The Verge . "The results are consistent with water, but I'd like to see more evidence before we say anything conclusive."
The radar measurements do not give any good indication of the thickness, so we do not know how deep this lake is going. It could be a deep body of water, or it could be a kind of mud mixed with many small stones. "We should not have a picture in our heads because we do not know," says Anja Diez, a geologist at the Norwegian Polar Institute, The Verge . "We only know where this water is, but we really know nothing about the depth."
Luckily we can get more answers about this area soon. In May, NASA launched a new lander named InSight on Mars to probe the interior of the Red Planet and determine its internal temperature. NASA's Green says the InSight's heat probe could tell us how much heat escapes the planet and whether liquid water under the South Pole is even sustainable. "This instrument could help us to understand that the heat is sufficient to keep this water fluid and not frozen," says Green.
InSight is not quite enough to really confirm the existence of the lake – if it is a lake. NASA would need to send a robot to drill on the ice or send a more powerful type of radar to Mars, which is more sensitive than the MARSIS instrument. There are currently no plans to send such a tool on a future Mars spacecraft. But Green says that this discovery could lead to discussions about what kind of tool is useful for sending. "NASA and other authorities have been discussing that," he says. "This will bring some urgency now."
A more powerful radar could also be able to extract other potential aquifers below the Martian surface – when they are there. The South Pole reservoir had to be quite large for MARSIS to pick it up, but a more sensitive instrument could detect even smaller pockets. Finding more of these hidden lakes, especially at lower, warmer heights, could greatly affect how we one day send people to Mars. If there is an aquifer under a good landing site, NASA could try to drill people there to drill into the ground and look for microbes.
"That could illuminate a network of underground aquifers that would hopefully be more convenient and then help us decide where people would land," says Green. "Because [water’s] is an important resource we must have."