The NASA Perseverance rover has been exploring Mars’ Jezero Crater since 2021, and its latest discovery provides strong evidence that the crater once held a lake billions of years ago. Using its onboard radar instrument called RIMFAX, Perseverance was able to see over 20 meters below the surface and identify distinct layers of sediment deposited in the crater over time.

This supports the idea that the crater environment changed from a lake to a river delta as the climate on Mars transformed in the ancient past. If life ever existed on Mars, the Perseverance rover’s verification of lake sediments at the base of Jezero Crater reinforces the hope that traces may be found in the crater.

Jezero Crater is located on the edge of Isidis Planitia, a giant impact basin. From orbital images, scientists saw clues that the crater contains rock and sediment layers deposited in a lake and river system.

But they couldn’t tell for sure if what we see today is how it originally formed or the result of billions of years of geological changes. Perseverance’s explorations on the ground are allowing researchers to better understand Jezero’s history.

As it drove across the crater floor and into the surrounding delta region earlier this year, Perseverance used RIMFAX to send radar pulses deep underground. By analyzing the reflected signals, scientists can create images showing the hidden layers below like slices through the ground.

The images clearly reveal two distinct periods of layered sediment deposition separated by periods of erosion. The bottom layers were deposited in an ancient lake within the crater, while the top layers formed as a river delta developed in a later wet phase.

This helps confirm previous hypotheses about Jezero’s past based on orbital data. Around 3 billion years ago, the crater was filled with water, leaving thick deposits of mud and silt along its edges. As the climate shifted, the lake disappeared and was replaced by a river feeding into the crater.

Over hundreds of millions of years, these sediments built up into a sprawling delta. Later, as Mars dried out again, the geological features in Jezero eroded closer to their current appearance.

The ability to see what lies buried deep underground with radar is revolutionizing our understanding of Mars’ ancient environments. Perseverance’s exploration of Jezero Crater is already providing a wealth of new information about the Red Planet’s watery history and may someday lead to breakthroughs in the search for signs of past life.


Sources

University of California Los Angeles (UCLA) | David Paige et al., Ground penetrating radar observations of the contact between the western delta and the crater floor of Jezero Crater, Mars, Science Advances (2024). DOI:10.1126/sciadv.adi8339


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