Researchers have uncovered evidence that Mars may have once had a vast ocean and coastal features, based on data collected by the Chinese rover **Zhurong**. A study published in the Proceedings of the National Academy of Sciences suggests that the red planet could have had a shoreline similar to Earth's, with waves and rivers transporting sediments toward a northern hemisphere ocean. This conclusion comes from ground-penetrating radar data gathered by **Zhurong**, which explored the Utopia Planitia region before entering hibernation in May 2022. The rover's instruments, including the Rover Penetrating Radar (RoPeR), allowed scientists to examine subsurface structures up to 100 meters deep. The data revealed 76 underground reflectors inclined toward the lowlands of the north, which researchers compared to Earth's coastal areas and found striking similarities. These structures, according to the study, resemble ancient beaches and river deltas, suggesting a dynamic interface between air and water. The researchers ruled out alternative explanations such as lava flows, sand dunes, and fluvial deposits, based on the measured permittivity of the layers and the absence of valley networks at the landing site. The findings suggest that these formations developed in a stable body of water rather than from temporary flooding or isolated melting events. The study concludes that these deposits correspond best to ancient sedimentary coastal structures, likely composed of sand and gravel transported by waves and currents from a Martian ocean that could have covered nearly half the planet. This discovery reinforces the hypothesis that the northern plains of Mars once hosted a vast and enduring ocean, with liquid water existing for an extended period. The study also adds to evidence suggesting that Mars experienced a warmer and wetter climate during the Late Hesperian period, about 3 to 3.5 billion years ago, conditions that could have been favorable to potential microbial life. The findings raise new questions about the fate of the ocean, including whether it evaporated into space as the Martian atmosphere thinned or if part of the water remains beneath the surface.