Scientists have confirmed that the Jezero crater on Mars once hosted a vast lake and river delta, increasing the chances of finding traces of life in the soil and rock samples collected by the Perseverance rover.
The confirmation comes from the Radar Imager for Mars’ Subsurface Experiment (RIMFAX), a ground-penetrating radar instrument on board the rover that can reveal the structure and composition of subsurface layers. The radar data shows that the crater filled with water, depositing sediments on the floor, and then shrank and formed a delta as the water level dropped. The sediments were later eroded by wind and water, creating the geologic features visible today.
The discovery supports the idea that the Jezero crater was once a habitable environment, where life could have emerged and evolved. The Perseverance rover has been collecting samples from the crater since 2021, which will be returned to Earth by a future mission and analyzed for signs of past life.
The research, led by UCLA and The University of Oslo, was published in the journal Science Advances on January 26, 2024. The team used images from orbit and radar measurements from the rover to reconstruct the geologic history of the crater, which is about 30 miles wide and located just north of the Martian equator.
“From orbit we can see a bunch of different deposits, but we can’t tell for sure if what we’re seeing is their original state, or if we’re seeing the conclusion of a long geological story,” said David Paige, a UCLA professor of Earth, planetary and space sciences and first author of the paper. “To tell how these things formed, we need to see below the surface.”
The radar data reveals that the lake sediments are about 20 meters thick and cover an area of about 100 square kilometers. The delta sediments are about 10 meters thick and cover an area of about 50 square kilometers. The radar also detected variations in the electrical properties of the sediments, which could indicate changes in mineralogy or porosity.
The researchers estimate that the lake existed for at least tens of thousands of years, and possibly much longer, during a period when Mars was warmer and wetter than today. The lake was fed by a river that carved a valley into the rim of the crater and deposited sediments at its mouth. As the climate changed and the lake dried up, the river became intermittent and formed a series of smaller deltas along the edge of the crater.
The erosion of the sediments over time exposed different layers of the lake and delta deposits, creating a complex stratigraphy that can be seen from orbit. The Perseverance rover has been exploring these layers and sampling them for future analysis.
“The discovery of lake sediments reinforces the hope that traces of life might be found in soil and rock samples collected by Perseverance,” Paige said. “If life ever existed on Mars, this would have been a good place to look for it.”