Today, we know of Mars as a cold, dry desert, with patches of subterranean ice and ice caps at its poles. Billions of years ago, however, liquid water flowed freely across the planet. And, while NASA's various Mars rovers have uncovered signs that such water once existed on Mars, there's perhaps no better evidence of an ice-free, shallow lake than these two sets of ripples in Martian rock.
In November 2022, NASA's Curiosity rover imaged the Amapari Marker Band in the foothills of Mount Sharp, located in Gale Crater. Within the marker band itself — a thin, dark layer of rock — scientists recognized wave ripples in what would've once been a sandy shoreline. A few weeks later, Curiosity imaged another set of wave ripples in the nearby Prow outcrop, which would have been on the lake bed.
