Traces of an ancient ocean on Mars have been found that could have contained life

The new work shows: this body of water may not have been a brief episode, but a stable water system that existed for about 0.8-1.5 million years. This is an important time frame for Mars: such an environment could have been long enough for the complex chemical processes associated with the possible origin of life. But the study found no traces of life itself.

The main clue was the "manganese ring" - a band of minerals similar to the trail that water leaves on the banks of a bed. On Earth, such mineral streaks can show ancient water levels. The authors believe that a similar trace on Mars could mark the shoreline of an ancient ocean.

Details

The researchers studied manganese compounds - oxides and hydroxides. These minerals are important because they are related to water and oxygen. In water with little oxygen, manganese can remain dissolved, and when exposed to a more oxidising environment, it can precipitate into solid mineral deposits.

Simply put, if water in an ancient reservoir met air, manganese minerals could accumulate at the boundary of these media. Over time, they could leave a "ring" on the planet's surface, a mineral trace of the former water level.

The team used infrared spectral data from the Chinese Mars rover Zhurong, as well as orbiting instruments from ESA and NASA. For the analysis, they applied the SCANet deep learning model trained on 13,742 infrared spectra of Martian soil analogues. This system helped recognise the signatures of manganese minerals in the short-wave infrared data.

The result was revealing: manganese minerals are not randomly distributed in the Utopia Plain. Their enrichment varies with altitude and forms a characteristic mineral "ring". According to the authors' interpretation, this indicates an ancient ocean with defined boundaries.

Based on the distribution of these minerals, scientists reconstructed several stages in the history of the reservoir: the emergence, expansion, retreat of water and final disappearance. The modelling showed that stable water conditions could have lasted from 0.8 to 1.5 million years.

This does not mean that Mars was like Earth with oceans and a rich biosphere. But it does mean that an aquatic environment could have existed for a long time in one of the planet's major basins. And water is one of the main factors that makes a place interesting to look for traces of past habitation.

Why it matters

Until now, Mars has often been described as a planet where liquid water appeared in short episodes: after impacts, volcanic activity or temporary climate changes. The new work suggests a different scenario for the Utopia Plain: a longer-lived water system may have existed there.

For the question of life, this is fundamental. Life does not arise just because there is water somewhere. You need the right chemical conditions, energy sources, and time. If a Martian ocean did exist for hundreds of thousands or more than a million years, that made the environment potentially more favourable for prebiotic chemistry - processes that could have preceded life.

Background

The Utopia Plain has long been of interest to planetologists. It is Mars' largest northern basin, and its geology preserves signs of ancient water activity. The new work adds a time frame to this picture: the authors have tried not just to show what water might have been, but to reconstruct how long it persisted and how it receded.

Manganese minerals are particularly valuable as a "geological archive". Their distribution can preserve information about the water-air boundary, the chemistry of the environment, and the changes in the body of water. In the case of Mars, this provides a rare opportunity to read the history of the ancient ocean not from a single feature, but from the spatial pattern of minerals.

The authors relate this history to the Hesperian epoch of Mars, a period when the planet transitioned from a wetter and more active past to a cooler and drier state. It is transitional periods like this that are important for understanding when Mars may have lost conditions potentially suitable for the long-term existence of surface water.

Source

Research: Bingxu Hou, Heng Sun, Zhaoyang Hu, Chunjiang Li, Dingquan Xue, Yanzhang Li, Yong Lai, Yuxuan Hu, Ziyu Wang, Honglei Lin, Jiaqi Zhu, Tianci Hua, Anhuai Lu, Xiangzhi Bai, Yan Li, "Manganese (Hydr)oxides record the dynamic evolution of a million-year Hesperian Ocean in Utopia Planitia, Mars", Nature Communications, 2026.