NASA's car-sized Perseverance rover parachuted down to a region of Mars called the Jezero Crater, a place planetary scientists suspect once teemed with water. Now, two years later, the space agency's scientists may have spotted evidence of a once "rollicking river."

The telltale formation, shown in the image below, shows curving rocks — which indicates past vigorous water flow — made of larger, coarse sediments.

"Those indicate a high-energy river that’s truckin’ and carrying a lot of debris. The more powerful the flow of water, the more easily it’s able to move larger pieces of material," Libby Ives, a researcher at NASA’s Jet Propulsion Laboratory, said in a statement. "It’s been a delight to look at rocks on another planet and see processes that are so familiar," Ives added.

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Scientists previously saw these curved shapes from space. The six-wheeled Perseverance rover — a laser-zapping laboratory on wheels — allowed them to look much closer.

Curved rock formations indicating evidence of vigorous past river flow on Mars. Credit: NASA / JPL-Caltech / ASU / MSSS

The mosaic picture shows a Martian area composed of 203 images joined together. The curves might be from a shifting river bank, or perhaps sandbars whittled down by billions of years of wind-driven sand-blasting. A question that looms large is what this powerful waterway was like back when Mars was a warmer, bluer planet.

"Scientists are now debating what kind of powerfully flowing water formed those curves: a river like the Mississippi, which winds snakelike across the landscape, or a braided river like Nebraska’s Platte, which forms small islands of sediment called sandbars," NASA wrote.

Generally, there's clear evidence, etched into the Mars desert, of a past, water-rich world. This includes dried-up lakes, dried streams, and even ancient waves.

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Yet there remains zero evidence of Martian life. Indeed, NASA's rovers have detected organic materials on Mars, which essentially means molecules like carbon that can compose life as we know it, but there's nothing suggesting primitive microbes ever lived on the surface (though the subsurface remains unexplored).

A primary mission of the Perseverance rover is to seek out hints of life, if it ever existed, however difficult the task might be. A good place to look is in an area that once harbored water — and perhaps a deep, vigorous river.