Perseverance rover confirms existence of ancient Mars lake and river delta

At the time Kodiak sediment deposition, inferred paleolake levels within Mars Jezero Crater. The red star is NASA's Perseverance Rover landing site. Background taken from the Context Camera mosaic (CTX).
NASA made the right choice when it chose the landing spot for its Perseverance Mars Rover, a life-hunting rover.

Perseverance touched down on February 28th at the Jezero Crater's floor. This was primarily due to previous Mars orbiter observations that suggested it had a large lake and a river delta.

Perseverance captured photos of the robot's early mission before it started roving. This confirms this interpretation according to a new study.

"Without driving anywhere the rover was capable to solve one of our big mysteries, which was that the crater was once an lake," Benjamin Weiss, co-author of the study and a professor of planet sciences at the Massachusetts Institute of Technology said in a statement. It was never clear that it was a lake until we actually landed there.

Related: Where can I find the most recent Mars photos taken by NASA's Perseverance Rover?

This image taken by NASA's HiRISE camera aboard NASAs Mars Reconnaissance Orbiter shows a view from orbit of the delta fan in Jezero Crater. It also shows the landing site for Perseverance rovers, informally Octavia E. Butler. Also shown are the hill Kodiak, the Delta Scarp, and the location for boulder-rich material. (Image credit: NASA/JPL-Caltech/University of Arizona)

For bold missions, this is a great site

Perseverance is a key component of the $2.7 billion mission. It will hunt for signs of past Mars life, and also collect and store dozens of samples to be returned to Earth. The rover supported and documented the first few flights of NASA's Ingenuity Mars helicopter. It is now flying independently on the Red Planet.

Based on data from spacecraft like NASA's Mars Reconnaissance Orbiter, Jezero Crater was found to be a suitable place for this work. Orbital imagery revealed a fan-shaped feature at Jezero. Mission team members thought it was a delta, meaning a place where a river turned into a lake around 3.7 billion years back. This depositing sediments could be evidence of ancient Martian microbes if they ever existed.

Researchers analyzed photos Perseverance took of the putative delta using its Mastcam Z imaging suite and its SuperCam camera. The new study was published online today (Oct. 7).

These photos show the delta's edge as well as an isolated butte called "Kodiak", which the team believes is an erosional remnant from the same formation. Kodiak imagery was particularly sharp. The team could see distinct layers of sediment in it that could only have been formed by a river.

Layers of sedimentary rock in the hill Kodiak at Mars' Jezero crater. The photo in the upper image is from Perseverance's Mastcam Z camera. It was taken at a distance of 1.39 miles (2.24 km). The lower image is a SuperCam Remote Microscopic Imager mosaic that shows distinctive inclined beds interspersed between horizontal beds. These are signs of deposition within a delta environment. (Image credit: NASA/JPL-Caltech/LANL/CNES/CNRS/IRAP/LPG/ASU/MSSS)

According to Nicolas Mangold (of the French National Center for Scientific Research, and the University of Nantes), the Kodiak observations "point unambiguously towards a deposition of river [sediments]] with a Delta and a lake." Space.com's co-lead author, Nicolas Mangold, said via email that the Kodiak observations "point clearly toward a river [sediments] with this delta and a Lake". Sanjeev Gopta, Imperial College London's co-lead writer, is also involved.

Mangold stated that this will allow us to limit the lake's level, which will enable us to create a scenario of delta formation and lake activity along Perseverance’s traverse. Also, it will help us identify the right layers for analysis and sampling.

Perseverance's observations showed that the ancient Jezero lake was approximately 330 feet (100 m) lower than the orbital data suggested. Mangold stated that this "marks a phase in the delta well after its formation."

He said that it was impossible to extrapolate to Jezero's beginning before Kodiak deposition, as the corresponding layers are further away in the Delta. Perseverance may be able give more results when it crosses the delta.

Water on Mars: Explorations and Evidence

Detail of the boulder beds in Jezero Craters' delta scarp, taken by the Perseverance Rovers SuperCam Remote Microscopic Imager. Scientists believe these boulders were moved using highly energetic water flows. (Image credit: NASA/JPL-Caltech/LANL/CNES/CNRS/IRAP/LPG)

Jezero is changing

Jezero, like all of the Martian surfaces, is currently bone-dry. Scientists believe that the Red Planet was dried up about 3.5 billion Years ago. This happened after the planet's global magnetic field collapsed and the atmosphere, which had once been thick, became vulnerable to being stripped by charged particles from the sun.

These photos, which have been analyzed by Perseverance, may offer a fascinating glimpse into the big shift. Perseverance's imagery shows large boulders up to five feet (1.55 m) in the upper (younger), layers of Jezero’s main delta outcrop. Study team members stated that it took a strong flow to transport these large rocks. This flood could have moved as high as 106,000 cubic feet (3,300 cubic m) of water per sec.

Mangold suggested that such flows could have been caused by "glacial surges", or rainfall-induced flash floods, like those found in some of Earth’s desert regions. Whatever the reason, the boulder-bearing deposits could indicate a different Jezero from the one that produced the lake sediments.

In the same statement, Weiss stated that the most remarkable thing about these images was the possibility to capture the moment when the crater changed from an Earth-like environment to the desolate landscape wasteland seen now. These boulder beds could be evidence of the transition. We have not seen it in any other locations on Mars.

If all goes according to plan, perseverance will eventually allow for close-up views of the delta formation. The team plans to drive the rover (which has covered 1.62 miles (2.61km) on Jezero's ground to date), over to the delta outcrop to collect samples from the calm-lake era. (Perseverance already has two of the planned many dozen samples. These will be taken to Earth by a NASA-European Space Agency joint campaign, possibly as early as 2031.

NASA's other Mars robots are temporarily suspended because Perseverance and NASA's other Mars robots are on the opposite side of the sun. NASA has instituted a communications blackout for two weeks to prevent our star from corrupting Mars-bound commands. This will end on October 16.

Mike Wall is the author and illustrator of "Out There" by Grand Central Publishing (2018). This book is about the search for alien life. Follow him @michaeldwall. Follow us on Facebook @Spacedotcom and Twitter @michaeldwall

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