Martian floods filled Jezero Crater, Perseverance finds

NASA’s Perseverance rover has spent the last eight months in the dry, forlorn landscape of Jezero Crater. But analysis of some of the rover’s first images have confirmed that roughly 3.7 billion years ago, the crater was home to an ancient lake fed by a river — one that occasionally experienced flash floods, washing boulders into the lake from up to tens of miles away.

When scientists chose Jezero Crater as the landing site for Perseverance, it was precisely because the site bore the hallmarks of an ancient lake. In its northwest corner, a channel leading into the crater ends with a fan-shaped plateau — clear evidence of a river depositing sediment into the lake, forming a delta. Now, scientists know for sure, marking their first efforts at reconstructing the history of this lost waterscape.

“This is the key observation that enables us to once and for all confirm the presence of a lake and river delta at Jezero,” said Nicolas Mangold, the paper’s lead author and a researcher at the Laboratories de Planétologie et Géodynamique in Nantes, France, in a NASA statement.

Reading the rocks

The research, published Oct. 7 in Science, is based on images taken during the rover’s first three months in Jezero by two of its cameras — Mastcam-Z and the SuperCam Remote Micro-Imager (RMI).

These cameras were able to zoom in on two regions roughly 1.3 miles (2.2 kilometers) away from the rover that contained exposed rocky outcrops that were not visible from orbit. Today, they look like buttes or cliffs, but their layers contain a geological record of bedrock that once lay on the bottom of Jezero’s lake.

One of these features, named Kodiak, is a butte west of the rover with exposed rock layers up to 25 meters high. Several places on the butte feature a distinct structure: a set of layers at a slanted angle, sandwiched between parallel rock layers above and below. “Never before has such well-preserved stratigraphy been visible on Mars,” said Mangold.