The central and ever-surprising story of water on ancient Mars took a new turn recently when NASA announced that the Perseverance rover had found the fossil remains of a once-powerful river in Jezero Crater.
From the nature and patterns of the riverbed turned to stone, to the ways that grains of sand and rocks been moved, textured and deposited and to the features of the surrounding landscape, the rover science team came go a speedy conclusion: This was a Mars river of substance. It carried substantial tonnages of sediment and rocks of some size, and laid down deep layers of sediment.
“We’re seeing what looks like the result of sudden, abrupt, high-energy inflow of water, carrying a lot of debris,” said Libby Ives, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory (JPL). “This was no tiny stream; it was a pretty big channel.”
But there’s more. The river was not only powerful it was also deep — especially where it apparently emptied into a large lake. This was a very different kind of water environment at ancient Jezero than what the previous NASA rover, Curiosity, found in Gale Crater.
“At Gale, you could wade through the water we found evidence for,” said Kathryn Stack Morgan, deputy science lead for Perseverance and formerly a member of the Curiosity science team.
“Here, we’re talking about scuba diving. This was really surprisingly deep.”
Mars scientists have long observed via orbiting satellites what they concluded were deep rivers on Mars. The area around the recently discovered riverbed actually had features that were interpreted from orbit to form a likely riverbed — part of a network of waterways that flowed into Jezero.
But Stack said that having the rover directly on the ancient riverbed, to have it observing and analyzing a substantial river that once existed, is a very different experience.… Read more