An aerial photo displays the remnants of a delta where an ancient lake was once fed by a water source at the Jezero crater on Mars. Credit: NASA/JPL-Caltech/ASUA discovery made by ground-penetrating radar aboard NASA’s Mars Perseverance rover revealed that the Jezero crater, formed by an ancient meteor impact just north of the Martian equator, once contained a large lake and river delta. Over time, sediment deposition and erosion within the crater shaped the current visible geologic formations on the surface today.The confirmation of lake sediments by the ground-penetrating radar strengthens the prospect of finding traces of life in soil and rock samples collected by Perseverance. An animation showing the RIMFAX instrument on NASA’s Mars Perseverance rover obtaining ground-penetrating radar measurements across the contact between the crater floor and the delta in Jezero crater, Mars was shared. Credit: Euibin Kim, David Paige, UCLAIf life ever existed on Mars, the verification of lake sediments at the base of the Jezero crater by the Perseverance rover increases the likelihood of finding traces within the crater. Resarch published in the journal Science Advances reveals that at some point, the crater was filled with water, depositing layers of sediments on the crater floor. Subsequently, the lake shrank and the sediments carried by the river formed a massive delta. As time passed, the lake dissipated, causing the crater’s sediments to erode and form the current geologic features visible on the surface today.
Mars Perseverance Rover RIMFAX ground penetrating radar measurements of the Hawksbill Gap region of the Jezero Crater Western Delta, Mars. Credit: Svein-Erik Hamran, Tor Berger, David Paige, University of Oslo, UCLA, California Institute of Technology Jet Propulsion Laboratory, NASAThe ground-penetrating radar indicates that periods of deposition and erosion occurred over extensive environmental changes, confirming the accuracy of inferences about the Jezero crater’s geologic history based on images of Mars obtained from space.“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 rover, equipped with seven scientific instruments and about the size of a car, has been exploring the 30-mile-wide crater, studying its geology and atmosphere, and collecting samples since 2021. The soil and rock samples gathered by Perseverance will be brought back to Earth by a future mission for further analysis for evidence of past life. The rover traveled from the crater floor to the delta, an expansive area of 3 billion-year-old sediments, from May to December 2022, resembling river deltas on Earth.
Mars Perseverance Rover RIMFAX ground penetrating radar measurements of the Hawksbill Gap region of the Jezero Crater Western Delta, Mars. Credit: Svein-Erik Hamran, Tor Berger, David Paige, University of Oslo, UCLA, California Institute of Technology Jet Propulsion Laboratory, NASAAs the rover traversed the delta, the RIMFAX instrument fired radar waves downward at 10-centimeter intervals and measured pulses reflected from depths of about 20 meters below the surface. With the radar, scientists can see down to the base of the sediments to reveal the top surface of the buried crater floor. Years of research with ground-penetrating radar and testing of RIMFAX on Earth have taught scientists how to read the structure and composition of subsurface layers from their radar reflections. The resulting subsurface image shows rock layers that can be interpreted like a highway road cut. “Some geologists say that the ability of radar to see under the surface is kind of like cheating,” said Paige, who is RIMFAX’s deputy principal investigator.
Mars Perseverance Rover RIMFAX ground penetrating radar measurements of the Cape Nukshak region of the Jezero Crater Western Delta, Mars. Credit: Svein-Erik Hamran, Tor Berger, David Paige, University of Oslo, UCLA, California Institute of Technology Jet Propulsion Laboratory, NASARIMFAX imaging revealed two distinct periods of sediment deposition sandwiched between two periods of erosion. UCLA and the University of Oslo report that the crater floor below the delta is not uniformly flat, suggesting that a period of erosion occurred prior to the deposition of lake sediments. The radar images show that the sediments are regular and horizontal — just like sediments deposited in lakes on Earth. The existence of lake sediments had been suspected in previous studies, but has been confirmed by this research.A second period of deposition occurred when fluctuations in the lake level allowed the river to deposit a broad delta that once extended far out into the lake, but has now eroded back closer to the river’s mouth.“The changes we see preserved in the rock record are driven by large-scale changes in the Martian environment,” Paige said. “It’s cool that we can see so much evidence of change in such a small geographic area, which allows us extend our findings to the scale of the entire crater.”Reference: “Ground penetrating radar observations of the contact between the western delta and the crater floor of Jezero crater, Mars” by David A. Paige, Svein-Erik Hamran, Hans E. F. Amundsen, Tor Berger, Patrick Russell, Reva Kakaria, Michael T. Mellon, Sigurd Eide, Lynn M. Carter, Titus M. Casademont, Daniel C. Nunes, Emileigh S. Shoemaker, Dirk Plettemeier, Henning Dypvik, Sanna Holm-Alwmark and Briony H. N. Horgan, 26 January 2024, Science Advances.
DOI: 10.1126/sciadv.adi8339The research was funded by NASA, the Research Council of Norway, and the University of Oslo.
