Ocean could lie beneath Mars' surface, study says

FILE - This April 30, 2021, image taken by the Mars Perseverance rover shows the Ingenuity helicopter, right, flying over the surface. Data gathered from the planet indicate there could be quite a bit of water well below the surface. (NASA via AP)

About 10 to 20 kilometers below the surface of Mars could be a large amount of water, a study published Monday in the Proceedings of the National Academy of Sciences says.