Martian Ocean Held More Water Than the Arctic

Researchers have determined that a primitive ocean on Mars may have once held more water than is currently found in Earth's vast Arctic Ocean. This paints a very different picture from the dusty Red Planet that we know today, and raises questions about where all that water could have gone.

That's at least according to a study recently published in the journal Science, which details how scientists determined how much water Mars once had by estimating how much was lost to space. They concluded that the Red Planet only boasts a mere 13 percent of all the water it once had - now locked up in vast swaths of ice at its poles.

"With this work, we can better understand the history of water on Mars," study lead Geronimo Villanueva, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said in a statement.

According to the estimates from Villanueva and his team, Mars would have had enough water to cover its entire surface in a liquid layer about 450 feet (137 meters) deep. Interestingly, that doesn't mean that the young Mars was a beautiful water-land. Instead, it was likely a world of contrasts, where a vast singular ocean likely occupied the great majority of its northern hemisphere. There, some portions of the ocean would have reached as deep as a mile or more, even while the southern side of the planet remained largely dry or even volcanic - with lava actually carving some of the canyons we see there.

To determine all this, the team compared the ratio of HDO to H₂O in water on Mars today to the ratio found trapped in a Martian meteorite dating back 4.5 billion years ago. The calculated differences allowed them to estimate what kind of atmospheric changes occurred over time, hinting at how much water was lost when the planet mysteriously lost a great deal of its atmosphere.

It was estimated that a great deal of water (about 87 percent of the planet's total volume) was lost - most of it coming from an ancient ocean that would have covered 19 percent of the planet's surface near the Martian Northern Plains. By comparison, the Atlantic Ocean occupies 17 percent of Earth's surface.

Still, such massive water loss doesn't happen fast, even in the wake of a violent event like a loss of atmospheric protections.

"With Mars losing that much water, the planet was very likely wet for a longer period of time than was previously thought, suggesting it might have been habitable for longer," added Michael Mumma, a senior scientist at Goddard.

This could give hope to experts searching for signs of past life on the Red Planet, with past and current rover missions dedicated to the task.

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