High-resolution images of a rocky Martian cliff taken by the Mars Reconnaissance Orbiter’s HiRISE camera suggest that rivers were once present on the surface of Mars about 3.7 billion years ago, due to the rocks’ similarities to those carved out by rivers on Earth, according to a study published in Nature Communications. “[T]he extremely high resolution imagery allowed us to ‘read’ the rocks as if you are standing very close to the cliff,” says study author Francesco Salese.
