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Oceans on Mars may have been more vast than we thought, a new study has suggested. A staggering 686 quadrillion metres cubed vast.
Back in 2015, the Curiosity rover trundled across the Martian surface, digging and sifting through the soil to see what it could learn. By April, it had reported back evidence of salty liquid water existing beneath the planet’s surface. It was suggested the water would collect in the soil at night, and evaporate during the day. Until that point, evidence had only pointed to frozen chasms of water on the cold planet, where temperatures can plunge to -90°C at night even in summer. The high salt content in the water, however, may be what allows for liquid water even at these temperatures.
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So, we know there are frozen bodies of water in Mars, that may have had the potential to be liquid oceans at some point. Now, geographers from the Northern Illinois University have estimated just how much water could have filled those oceans by studying the planet’s topography.
In particular, they looked at how much water was needed to carve the peaks and troughs of the mountainous Martian surface. The theory works off the basis - and backs up the concept - that Mars once had oceans that would evaporate then pour down valleys as rainfall, in a hydrologic cycle similar to Earth’s own.
Taking into account the time it took to form the valleys (more than three billion years), professor Wei Luo and colleagues developed an algorithm to form their predictions. Using high-resolution imaging, they were able to identify the size of valleys based on their colour and work from there.
“Our most conservative estimates of the global volume of the Martian valley networks and the cumulative amount of water needed to carve those valleys are at least ten times greater than most previous estimates,” Luo concluded in a statement. In fact, by their calculations, 4,000 times the volume of the valleys was needed in water to carve the landscape. “That means water must have recycled through the valley systems on Mars many times, and a large open body of water or ocean is needed to facilitate such active cycling,” Luo said. “I would imagine early Mars as being similar to what we have on Earth — with an ocean, lakes, running rivers and rainfall.”
In a paper on the study, published in Nature Communications, the team argues that prior attempts to estimate the water quantity were based on “local sites”.
“We employed an innovative progressive black top hat transformation method to estimate them on a global scale based on the depth of each valley pixel,” the researchers write. The resulting picture of the Martian climate could, therefore, take into account every tributary and stream surrounding the valleys. The resulting quantities, they argue, are “consistent with an early warm and wet climate with active hydrologic cycling involving an ocean”.
How that could have been possible, however, remains a mystery. Luo points out in a statement that Mars is further from the Sun, and billions of years ago the Sun would have been less intense. According to climate models in use today, Mars could not have had the heat that would be necessary to form a hydrologic cycle based on evaporation and rain. This is a pretty vast gap in the hypothesis so, in essence, we are nowhere near concluding that there were, in fact, liquid oceans on Mars. Let alone oceans of the magnitude being suggested by the Northern Illinois team.
This article was originally published by WIRED UK
