Life on Mars? It once had an ocean with sandy beaches, researchers claim

Perth: In the 1970s, images from the NASA Mariner 9 orbiter revealed water-sculpted surfaces on Mars. This settled the once-controversial question of whether water ever rippled over the red planet.

Since then, more and more evidence has emerged that water once played a large role on our planetary neighbour.

For example, Martian meteorites record evidence for water back to 4.5 billion years ago. On the young side of the timescale, impact craters formed over the past few years show the presence of ice under the surface today.

Today the hot topics focus on when water appeared, how much was there, and how long it lasted. Perhaps the most burning of all Mars water-related topics nowadays is: were there ever oceans?

A new study published in PNAS has made quite a splash. The study involved a team of Chinese and American scientists led by Jianhui Li from Guangzhou University in China, and was based on work done by the China National Space Administration’s Mars rover Zhurong.

Data from Zhurong provide an unprecedented look into rocks buried near a proposed shoreline billions of years old. The researchers claim to have found beach deposits from an ancient Martian ocean.

Blue water on a red planet

Rovers exploring Mars study many aspects of the planet, including the geology, soil and atmosphere. They’re often looking for any evidence of water. That’s in part because water is a vital factor for determining if Mars ever supported life. Sedimentary rocks are often a particular focus of investigations, because they can contain evidence of water – and therefore life – on Mars.

For example, the NASA Perseverance rover is currently searching for life in a delta deposit. Deltas are triangular regions often found where rivers flow into larger bodies of water, depositing large amounts of sediment. Examples on Earth include the Mississippi delta in the United States and the Nile delta in Egypt.

The delta the Perseverance rover is exploring is located within the roughly 45km wide Jezero impact crater, believed to be the site of an ancient lake.

Zhurong had its sights set on a very different body of water – the vestiges of an ancient ocean located in the northern hemisphere of Mars.

The God of fire

The Zhurong rover is named after a mythical god of fire. It was launched by the Chinese National Space Administration in 2020 and was active on Mars from 2021 to 2022. Zhurong landed within Utopia Planitia, a vast expanse and the largest impact basin on Mars which stretches some 3,300km in diameter.

Zhurong is investigating an area near a series of ridges – described as paleoshorelines – that extend for thousands of kilometres across Mars. The paleoshorelines have previously been interpreted as the remnants of a global ocean that encircled the northern

third of Mars.