Did Mars once had a huge ancient ocean? New evidence found in unusual Martian clay mounds

Some Martian buttes and mesas on the Red Planet's northern plains contain eroded mounds with clay layers formed by liquid water. (Image: ESA)

Researchers have discovered thousands of hills on Mars. These mounds contain clay minerals, indicating the planet once had water. The findings reveal that liquid water existed nearly four billion years ago, transforming Mars' climate dramatically.

Mars' northern plains and their watery past
The study, led by Joe McNeil of the Natural History Museum, examined Mars' northern plains. Using data from NASA and ESA missions, they identified over 15,000 clay-rich mounds. These formations suggest long-term water activity, possibly from an ancient ocean.

The mounds, up to 500 metres tall, consist of layered deposits. They are located in Chryse Planitia, a region shaped by water and wind erosion. The clay layers formed during Mars' Noachian era, a period of significant water presence.

Future exploration aims to solve Mars' mysteries
The Rosalind Franklin rover, launching in 2028, will explore Oxia Planum, near the clay mounds. Scientists hope to uncover signs of past life and confirm the existence of an ancient ocean.

The findings, published in Nature Geoscience on 20 January, provide fresh insights into Mars' wet history and its potential to harbour life.