Mars once had an ocean with sandy beaches, researchers say

Mars may not seem like a prime holiday spot with its arid landscape and punishing radiation levels, but it once boasted beaches, researchers have found.

While previous discoveries of features including valley networks and sedimentary rocks has suggested the red planet once had flowing rivers, there has been debate among scientists over whether it also had oceans.

Now researchers say they have fresh evidence to support the idea after discovering buried beaches on Mars.

Writing in the Proceedings of the National Academy of Sciences, the scientists report how they made the discovery after they analysed below-ground imaging data from China’s Zhurong rover.

“Zhurong was sent to southern Utopia Planitia near locations where paleoshorelines have been mapped from satellite data,” said Dr Benjamin Cardenas, a co-author of the research from Penn State University.

The authors say the results from the northern lowlands of Mars are similar to those obtained at shorelines on Earth using ground-penetrating radar: both indicate features in the subsurface material that are tilted – and with a similar angle – towards the lowland, or ocean, direction.

“Typically the radar picks up on even subtle changes in sediment size, which is probably what’s happening here,” said Cardenas.

The researchers say this Martian beach appears to have shifted position over time. The data reveals a series of features dipping towards the north – something Cardenas said indicated the beach grew out into the ocean. “In fact, it grew at least 1.3km north into the ocean.”

Cardenas said the implications were exciting. “It’s a simple structure, but it tells you there had to be tides, there had to be waves, there had to be a nearby river supplying sediment, and all these things had to be active for some extended period of time,” he said.

While the researchers noted that tilted features could arise from other types of activity, they say none of these explain the data. “We rule out volcanic, rivers, and wind-blown sand dunes. All of these are pretty commonly seen on Mars, but the structure just doesn’t fit any of them,” said Cardenas.

He added that the discovery had implications for understanding the past habitability on Mars. “A beach is an interface between shallow water, air and land. It’s these sorts of environments where it’s thought life first came to be on Earth, and I think it would be a great place to send a follow-up mission looking for signs of past life,” he said.

But while the Martian shoreline may have been sandy, the similarities to beaches on Earth are limited: not only would there have been a lack of palm trees and gulls but, Cardenas said, it would probably have been fairly chilly.

“That said, I’d love to have seen it. Doing geology, reconstructing these ancient landscapes, it really is excellent daydream fuel,” he said.