Mars as a Water World: Evidence for a Global Ocean 4.5 Billion Years Ago

Were there oceans on Mars? Scientists have long debated where they came from, how large they were, how deep they reached, and where they went. Numerous recent studies now point to the existence of at least one ancient ocean on the Red Planet.

Recently, researchers reported a possible giant ancient coastline on Mars dating to about 3.5 billion years ago. Now a team of Danish astronomers and astrophysicists concludes that 4.5 billion years ago young Mars may have been covered by a global ocean at least 300 meters deep — and perhaps much deeper — making the planet potentially suitable for some forms of life.

What did the researchers find out?

If you imagine a physical map of young Mars, calling it the Red Planet would be misleading. It may have looked more like Earth — a bluish, wet, and warm world rather than an icy, dusty one.

A team led by Martin Bizzarro, a professor at the University of Copenhagen, found that early Mars was bombarded by ice-rich asteroids. The team estimates those impacts occurred during Mars’ first 100 million years, and Sci.News reports that the water delivered by those asteroids around 4.5 billion years ago would have been enough to blanket the planet in a global ocean.

To reach that conclusion, the researchers analyzed variations in chromium-54 isotopes in 31 Martian meteorites that fell to Earth; some of those rocks were part of Mars’ original crust.

They also found that the impacting asteroids delivered biologically important molecules, including amino acids, to Mars. Those organic compounds could have helped seed the conditions needed for life to emerge.

Bizzarro and his team say the ocean could have covered all of young Mars. They estimate its depth at no less than 300 meters and possibly up to a kilometer. Mars’ lack of plate tectonics made it possible to read this part of the planet’s early history.

Because Earth’s lithospheric plates constantly move and recycle, evidence from the planet’s first 500 million years has been erased. By contrast, Mars’ surface preserves records from its early history.

The study was published in the journal Science Advances.

For reference Mars is 4.65 billion years old. The period of early Mars ended about 4 billion years ago.