Ancient Traces of a Giant Ocean Just Discovered on Mars: ScienceAlert

Ancient Traces of a Giant Ocean Just Discovered on Mars: ScienceAlert

You will no doubt be familiar with the dry, dusty look of Mars how it looks today — but scientists have found evidence of a huge ocean that existed on the surface of the red planet about 3.5 billion years ago, likely spanning hundreds of thousands of square miles.

That evidence comes in the form of distinctive coastline topography, identified by numerous satellite images of the Martian surface. When these images are taken at slightly different angles, a relief map can be built.

Researchers have been able to map more than 6,500 kilometers (4,039 miles) river ridgesapparently carved by rivers, showing that they are most likely eroded river deltas or submarine canal belts (channels carved into the seabed).

Gale crater landscape
The bottom of Gale Crater, near a region called Aeolis Dorsa, which researchers believe was once a vast ocean. (NASA/JPL-Caltech/MSSS)

“The big, new thing we did in this article was think about Mars in terms of its stratigraphy and its sedimentary record,” says geoscientist Benjamin Cardenas from Pennsylvania State University.

“On Earth, we map the history of waterways by looking at sediment that has been deposited over time. We call that stratigraphy, the idea that water transports sediment, and you can measure the changes on Earth by understanding how sediment piling up. That’s what we’ve done here – but it’s Mars.”

Using data from the Mars exploration orbiter collected in 2007, the team applied an analysis of the ridge thicknesses, angles and locations to understand the area of ​​study: the topographic depression known as the Back of the Aeolians region on Mars.

It seems likely that a significant amount of change took place on this part of the planet all those years ago, Cardenas explains. This is evidenced by the evidence of significant sea level rise and the rapid movement of rocks through rivers and currents. Today, Aeolis Dorsa contains the most concentrated collection of river ridges on Mars.

All this ties in with the search for life on Mars. One of the most fundamental questions scientists are looking at regarding the red planet is whether it has ever had conditions hospitable enough to sustain life.

“What immediately comes to mind as one of the key points here is that the existence of an ocean of this size means a higher potential for life,” says Cardenas.

“It also tells us about the ancient climate and its evolution. Based on these findings, we know that there must have been a period when it was warm enough and the atmosphere was thick enough to support so much liquid water at once.”

The researchers do not stop at the Aeolis Dorsa region.

in a separate study published in Natural Geosciencessome of the same researchers, including Cardenas, have applied an acoustic imaging technique used to map ancient seafloors in the Gulf of Mexico to a model of how water may have eroded the surface of Mars.

There are vast swaths of what may be river ridges all over Mars, and the simulations run by the team are remarkably similar to the shape of the landscape on the red planet — suggesting extensive water cover once existed.

We see Lake and Lake signs that water was once abundant on Mars, and work continues to figure out where it led and where is that water now – although it is not easy to look back billions of years.

“If there were tides on ancient Mars, they would have been here, gently bringing water in and out,” says Cardenas. “This is exactly the kind of place where ancient Martian life could have evolved.”

The research was published in Journal of Geophysical Research: Planets and Natural Geosciences.

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