Astro Bob: Perseverance rover finds evidence of raging river on Mars

How a rollicking river left its mark on the Red Planet. We also look ahead to the return of the young moon at dusk.

Martian river bed
Scientists think that the bands of rocks seen in this image may have been formed by a very fast, deep river on Mars. NASA’s Perseverance Mars rover captured the panorama between Feb. 28 and March 9 at a location nicknamed “Skrinkle Haven." The mosaic is made up of 203 individual images that were stitched together after being sent back from Mars. This natural color view is approximately how the scene would appear to an average person if they were on Mars.
Contributed / NASA, JPL-Caltech, ASU, MSSS

Mars is just a scintilla of light in the constellation Gemini seen from Earth. But thanks to the Martian rovers Curiosity and Perseverance we can imagine what it would like to be there in person, filling up our senses the way the home planet does each waking day.

Jezero crater delta
The Perseverance rover landed near of the ancient river delta in Jezero Crater on February 2021. Despite its age the delta resembles current river deltas on Earth.
Contributed / NASA, JPL-Caltech

NASA recently released a spectacular montage that shows curving bands of rock deposited as sediments by a deep, fast-flowing river. The river was part of a network of waterways that flowed into Jezero Crater, where the Perseverance rover has been exploring for more than two years. When Mars was a wetter, more life-friendly place 3.5 billion years ago, rain and rivers turned the 28-mile-wide (45 kilometers) crater into a lake you could have gone sailing on.

Sometime after, the combined effects of the planet's lower mass (weaker gravitational pull) and lack of a global-wide protective magnetic field caused some of the water in Jezero and elsewhere to evaporate into space. But to this day a significant amount remains locked up in minerals such as clays, carbonates and sulfates in the Martian crust.

Perseverance location
This map shows the location of the Mars Perseverance rover and helicopter Thursday, May 18, near the rim of Belva Crater within the ancient delta. Since landing in February 2021 the rover has driven 11.6 miles (18.6 kilometers).
Contributed / NASA, JPL-Caltech

So, yes. Mars still retains plenty of water albeit hidden from direct view. Discovery of water-rich minerals as well as abundant evidence of rivers, lakes and even oceans motivate the continuing search for signs of ancient microbial life , precisely the purpose of the Perseverance rover. Since early 2021 it's been drilling, sampling and caching promising samples for later return to Earth and keeping an eye out for any potential fossils.

Mars river bed
This closer view of the ancient river bed from March 1 shows multiple curving rock formations and includes the rover's drill (left).
Contributed / NASA, JPL-Caltech

Those strikingly curvy rows of rocks in the photos sit atop an 820-foot-tall (250 meters), fan-shaped pile of sedimentary rock in the middle of a massive river delta. The delta formed billions of years ago when a river and its tributaries deposited loads of silt as they drained through a gap in wall of the crater.


River cobble
A possible cobble on the sandy surface of Mars photographed March 7.
Contributed / NASA, JPL-Caltech

While NASA's Curiosity rover found evidence of shallow streams in Gale Crater several years back, Perseverance has photographed coarse sediment grains and cobbles — water-rounded rocks larger than pebbles but smaller than boulders — that indicate a high-energy river carrying a lot debris. Fast-flowing, deep water moves larger pieces of material more easily.

Pinestand sediments
A second mosaic by Perseverance shows a separate location that is part of the same, curving-rock landscape and about a quarter mile (450 meters) from Skrinkle Haven. “Pinestand” is an isolated hill with sedimentary layers that curve skyward, some as high as 66 feet (20 meters). Scientists think these tall layers may also have been formed by a powerful river.
Contributed / NASA, JPL-Caltech, ASU, MSSS

While mission scientists are convinced a powerful river once flowed here they're still debating whether it was like the Mississippi which winds snakelike across the landscape or a braided river dotted with sandbars like Nebraska's Platte. The curved layers ripple out across the Martian landscape — were they riverbanks that shifted over time or former sandbars? The layers were likely much taller in the past but have been sandblasted by wind over the eons:

“The wind has acted like a scalpel that has cut the tops off these deposits,” said Michael Lamb of Caltech, a river specialist and Perseverance science team collaborator. “We do see deposits like this on Earth, but they’re never as well exposed as they are here on Mars. Earth is covered in vegetation that hides these layers.”

Scientists continue to study the rover photos as well as the data from its ground-penetrating radar for a better understanding of the planet's aqueous past. All the evidence is there, but like those easy meals where you "just add water," we can employ our imaginations to to do the same when viewing these barren landscapes. To peruse the rover's daily image upload check out the Perseverance raw images site .

Moon returns at dusk

Crescent return
The moon is back! Of course, it's always been there but recently only visible in the morning sky. Look for it very low in the northwestern sky starting Saturday, May 20.
Contributed / Stellarium

Just a heads up on the moon. The thin day-and-a-half-old crescent will grace the northwestern sky Saturday, May 20. You'll need an unobstructed view in that direction to see it best. Look for it about 30-35 minutes after sunset well below and to the lower right of Venus. The view through binoculars should be inspiring — as long as the wildfire smoke parts!

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at
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