Scientists have used orbiters and rovers to find dried streams, lakes, and gullies on Mars that hint at its watery past, but their cavalry of robots has struggled to prove the Red Planet ever had an actual ocean.

The evidence comes from data collected by China’s Zhurong Mars rover, which landed in the Utopia Planitia region of Mars in 2021. Unlike other rovers traversing the planet, Zhurong arrived with high- and low-frequency radar systems that allow it to conduct ground-penetrating scans of the Martian subsurface.