Mars once had oceans and beaches

Previous explorations had found valleys and sedimentary rocks on Mars, and it was thought that rivers once flowed on the planet. However, scientists have long debated whether or not Mars has oceans.

Now, data from China's Zhurong rover has added a new dimension to this debate.

Underground imaging data provides new evidence

In the study, published in the journal Proceedings of the National Academy of Sciences, scientists examined underground imaging data from the Zhurong rover. "Zhurong was sent to the southern Utopia Planitia region, where paleocoastlines were mapped using satellite data," said Dr. Benjamin Cardenas of Penn State University.

The researchers noted that the data from the northern lowlands of Mars are similar to ground-penetrating radar measurements used on Earth's coasts. In both cases, the subsurface material appears to slope toward the lowlands, or ocean.

Coasts may have changed over time

Data from Zhurong suggest that Martian coastlines have shifted over time. “The data suggest that the coastline has moved northward by at least 1.3 km,” Cardenas said.

"This may seem like a simple structure, but here we see evidence of tides, waves and a nearby river transporting sediment. Moreover, this process must have been active over a long period of time," said Cardenas, noting that this finding has important implications.

Traces of life may be sought on Mars

The researchers accept that the sloped structures could have been formed by other geological processes, but they state that the data obtained do not match these scenarios. "We have ruled out possibilities such as volcanic activity, rivers or wind-blown sand dunes. Although these are common formations on Mars, the structure detected here does not fit any of these processes," Cardenas said.

The discovery is an exciting development for scientists investigating the possibility of past life on Mars. "A coast is a point of interaction between shallow water, air and land. It is thought that life first emerged on Earth in these types of environments. So it would be great to send a new exploration mission to this region to look for signs of past life on Mars," Cardenas said.

But ancient coastlines on Mars bear little resemblance to tropical beaches on Earth. Even without palm trees or seagulls, Cardenas expressed great curiosity to see the beaches: "Reconstructing these ancient landscapes is one of the most exciting aspects of geology. It really is worth dreaming about!" he said.