Scientists have calculated how much water Mars may have once had – and it turns out it could be rather a lot.
The study published in Nature Communications, led by Professor Wei Luo from the Northern Illinois University, estimates there may have been as much as 686 quadrillion cubic meters (15 zeroes), which is 10 times more than previous estimates and almost exactly half the amount of water on Earth (1,390 quadrillion cubic meters).
This seems to support the idea that Mars had a warmer climate and an active water cycle that evaporated and rained down again. This would also explain how some of the canyons on Mars formed like Valles Marineris, the largest canyon in the Solar System, which is 10 times the length of the Grand Canyon.
"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 10 times greater than most previous estimates," Luo said in a statement.
Most of the valleys on Mars are more than 3 billion years old, which ties in with when we think the Red Planet had water. This is estimated anywhere from 3.1 to 3.8 billion years ago, until the planet lost its magnetic field and the atmosphere was blown away, evaporating the water.
Luo used an algorithm to work out the amount of water that would have been needed to create the valley networks. The water would have supposedly been recycled through the valleys many times, and only a large body of water would allow this to happen. "I would imagine early Mars as being similar to what we have on Earth – with an ocean, lakes, running rivers and rainfall," Luo said.
Don’t go packing your swimsuit just yet, however, as the existence of the ocean is not guaranteed. For one thing, the resultant figure seems dubiously large. It’s 10 times bigger than has previously been estimated for the northern hemisphere of Mars, and it’s 4,000 times greater than the volume of the valley cavities on Mars.
None of our models can currently create a Mars that was warm enough to support such an extensive water cycle. And we haven't seen much physical evidence for the ocean either. Speaking to Gizmodo, Tanya Harrison from Arizona State University said that we currently “don’t see strong morphological evidence to support the former presence of an ocean.”
We have seen tentative evidence for an ancient shoreline on Mars, however. So if this ocean did exist, perhaps it was truly, completely, stupendously big.