Mars today is a cold, dry, dusty planet with its only obvious water locked up in frozen polar ice caps. But billions of years ago, it appears to have had sandy beaches lapped by waves along the shoreline of a vast ocean. The latest evidence for beaches on Mars comes from a Chinese Zhurong rover that landed on the planet in 2021. During its short life it detected evidence of underground beach deposits in an area thought to have once been the site of an ancient sea, bolstering the idea that the planet long ago had large bodies of water.