Mars is known for its crimson, frozen terrain, but a recent discovery by a team of researchers provides new evidence that there was once an ancient ocean in the now-challenging Martian terrain.
This discovery is proof that Mars was, at one point in its history, quite different – a hot, humid planet. Evidence for a 3.5 billion-year-old, 900-meter-thick shoreline in Mars’ northern hemisphere also hints at the possibility that life may have developed on the planet, which could be a boon for those who hope to find evidence of extraterrestrial life.
“This is one of the great scientific questions of humanity,” says Gregory Fiete, professor of physics at Northeastern. “It’s a matter of the present because we don’t yet know if there is life elsewhere outside of Earth.”
“We know that on Earth, life was born very early in the ocean, so at the same time it could have been born on Mars if Mars had an ocean. Whatever time the water was there, it is probably long enough according to the earth’s clock for life to have originated there.
In the scientific community, there has been an ongoing debate about whether the low-lying northern hemisphere of Mars could be the site of an ancient ocean. Using tools developed by the United States Geological Survey and map data from NASA and the Mars Orbiter laser altimeter, the team began mapping the planet’s northern zone. What they discovered were more than 6,500 kilometers of ridges, which they grouped into 20 systems.
By examining sediment accumulation, direction of erosion, and other stratigraphic evidence, the researchers were able to determine that these ridges were likely eroded river deltas or the remnants of an ancient Martian shoreline.
“The sediments in this basin are pouring in, slowly filling it over time, liquid water is building up, and that’s pretty conclusive evidence that this basin filled slowly over time and was an ocean of liquid water,” says Jaqueline McCleary, assistant professor of physics at Northeast.
At the same time, it provides pretty compelling evidence for a hot and humid period in Mars’ history. The slow, steady filling of this northern basin could not have happened if conditions on Mars were as they are now.
“That means the atmosphere was much thicker, so it would have trapped heat from the sun, so it was at a temperature where there could be liquid water,” Fiete says.
Given that current science indicates that life evolved in the oceans on Earth, Fiete says the presence of an ocean during a warm, humid period for Mars is promising evidence that some form of life may have also evolved. develop on Mars around the same time.
“Earth also had an ocean early in its history, and I think one of the most intriguing things about this discovery is that we know on Earth that life appeared very shortly, at geologic time scales, after Earth was created,” Fiete said. . “Perhaps a few hundred million years or so after these oceans existed on Earth, or very soon after Earth itself existed, we see the first signs of life on Earth. It’s a period that coincides with this ocean on Mars that was discovered.
To go further: if life could have developed on Mars and on Earth from a common set of conditions, it stands to reason that there is life elsewhere in the cosmos.
“This greatly increases the likelihood that life is elsewhere in the universe because two places with similar conditions both have life,” says Fiete. “It means that the origin of life is not an anomalous event.”
McCleary says one of the most exciting ramifications of this discovery is that the stratigraphic methods used by these researchers could help scientists uncover physical evidence of Martian life in the future.
“Because on Earth, where we see sedimentary layers, we also see a fossil record, one could also theoretically dig into the Martian surface and examine the geologic levels and look for a fossil record,” McCleary explains.
The technology to dig 900 meters into Mars does not currently exist, but Fiete says there are also quantum technologies that could be used to find evidence of Martian life. Radiocarbon dating uses the decay of radioactive isotopes of carbon to date objects made from carbon. Fiete says something similar could be used on Mars to pinpoint the location of an imbalanced number of isotopes, which, while not fossils, are also proof that life was once present.
“It’s kind of like a ghost of life,” says Fiete. “We don’t find something as concrete as a fossil, but you find physical signatures that life was there because there are abnormal concentrations of certain isotopes and elements.”
Methodologically, McCleary says this study is further evidence that interdisciplinary “cross-pollination” can help drive innovation and discovery. These researchers used an established technique in a new context and discovered something that could potentially change the way we think about our place in the universe.
“You have the search for extraterrestrial intelligence looking for this intelligent life, sending out probes, and throughout life there has been ancient life on the next planet, which is evocative and exciting for a species that continually seeks to understand itself and also seeks things like it elsewhere in the universe,” McCleary says.
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