An ancient coastal zone has been discovered in the southern region of Mars' Utopia Planitia.

The hypothesis that an ancient ocean once existed in the northern lowlands of Mars, potentially influencing the planet's early climate and atmosphere, has long been a topic of discussion within the scientific community. Previous research results have revealed potential shorelines and other geological features that support the notion of water being present in this region. In particular, crater-like formations often occurred in areas where water or ice once existed.

Now, a research team led by Bo Wu from the Hong Kong Polytechnic University has analyzed the geomorphological features of the landing site of "Zhurong" and found signs indicating the presence of a coastal zone in the southern part of Utopia Planitia — one of the largest impact basins on Mars. The sedimentary rocks, layered deposits, and multi-layered subsurface layers identified by the rover are typical structures found in environments with water.

Instead of the planned three months, "Zhurong" operated on the Martian surface for a whole year. During this time, the rover traveled about two kilometers across the bottom of Utopia Planitia, studying its geological features.

The authors of the study, published in the journal Scientific Reports, divided the investigated area into three geologically distinct regions. The first represents a terrain where a transition between land and ocean likely occurred. In the second area, the water depth was relatively shallow, while in the third, it reached significant depths.

Since the onboard rover radar, RoPeR (Rover Penetrating Radar), was able to "see through" the depths of the Red Planet up to 100 meters, the research team, based on the obtained data (as well as satellite data and their analysis), presented their version of events in the southern part of Utopia Planitia.

According to the scenario described by the team, the ocean formed as a result of flooding approximately 3.65-3.68 billion years ago and then froze, exposing the shoreline (which led to the formation of shallow and deep-water areas). Ultimately, around 3.4 billion years ago, the ocean completely disappeared, losing its subsurface volatiles.

However, the authors of the scientific work noted that their discovery does not prove the existence of an ancient ocean on Mars, and to clarify all uncertainties, it is necessary to bring Martian rocks to Earth for thorough study. Nevertheless, the results of the research provided important information supporting this hypothesis and contribute to a better understanding of the planet's geological history. The team plans to continue their research by conducting additional analysis of the data obtained from "Zhurong" and other Martian missions.