By Will DunhamWASHINGTON, March 18 (Reuters) – Using ground-penetrating radar, NASA’s Perseverance rover has detected underground remains of an ancient river delta on Mars in some of the oldest evidence yet obtained showing how water once flowed on the surface of Earth’s planetary neighbor.Researchers said the six-wheeled rover revealed geological features up to 115 feet (35 meters) underground while traversing 3.8 miles (6.1 km) of terrain inside Jezero Crater, an area in the Martian northern hemisphere believed to have been flooded with water and home to an ancient lake basin long ago.AdvertisementAdvertisementPerseverance identified layered sediments and eroded surfaces indicative of a delta environment, a large-scale fan-shaped deposit of sediment formed at the location where a river enters a larger body of water like a lake. They estimated that the now-buried delta dates to about 3.7 to 4.2 billion years ago. Mars, like Earth, formed roughly 4.5 billion years ago, meaning this delta existed relatively early in its history.The researchers said this delta predated a similar nearby surface feature called the Western Delta that dates to about 3.5 to 3.7 billion years ago.The rover’s RIMFAX instrument sends radar pulses downward and records pulses bouncing back off underground features, allowing a three-dimensional mapping of the subsurface. The new findings were based on RIMFAX’s deepest data col …
