The Martian landscape continues to reveal secrets of its past, and the latest discovery from NASA’s Perseverance rover suggests the planet may have been habitable for a longer period than previously thought. Using a sophisticated radar instrument, scientists have detected evidence of an ancient, buried river system within Jezero Crater, indicating multiple periods of water activity stretching back billions of years. This finding, published in the journal Science Advances, significantly expands the window for potential past life on Mars.
Jezero Crater, a 45-kilometer-wide impact crater, was already known to harbor evidence of an ancient lake and river delta – the Western Delta – visible from orbit. This made it a prime landing site for Perseverance, launched with the goal of searching for signs of past microbial life. However, the rover’s ground-penetrating radar, known as RIMFAX (Radar Imager for Mars’ Subsurface Experiment), has now revealed a more complex history hidden beneath the surface. The discovery of this older, deeply buried delta system suggests that Jezero Crater experienced at least two distinct periods of significant water flow, potentially separated by hundreds of millions of years.
“With this new finding, we extend the potential habitability period for Jezero significantly,” explained Emily Cardarelli, a geomicrobiologist at the University of California, Los Angeles, and lead author of the study. The research details how RIMFAX works by sending radar waves into the ground and analyzing the returning signals, much like an ultrasound. This allows scientists to map subsurface structures and determine their depth. Perseverance has been able to penetrate up to 35 meters below the Martian surface, a depth exceeding previous measurements.
Unlocking Mars’s Ancient Past
The key to this deeper penetration lies in the “Margin Unit,” a highly calcareous rock formation along the crater’s edge. According to Cardarelli, RIMFAX performs exceptionally well in this area, even better than on Earth, because the Martian subsurface contains fewer obstructions to the radar signals. The radar images reveal distinct layering within the underground, indicating the presence of buried sedimentary structures. This discovery suggests that the Jezero Crater wasn’t simply filled with water once, but experienced multiple phases of fluvial activity – periods of flowing water – over an extended timeframe.
The newly discovered system is estimated to originate from a geological epoch between 4.2 and 3.7 billion years ago, pushing back the potential timeframe for Martian habitability. The longer water persisted on the planet, the more time there was for microbial life to potentially develop and leave behind detectable traces. Although the exact duration of Mars’s habitability remains unknown, this finding provides a crucial piece of the puzzle.
A Promising Location for Biosignatures
The calcareous deposits of the “Margin Unit” are particularly promising in the search for evidence of past life. These types of formations are known to be capable of preserving organic molecules for billions of years. Whether such molecules are actually present remains to be seen, and will require analysis of the rock samples currently being collected by Perseverance for eventual return to Earth. NASA’s Perseverance rover is specifically designed to identify and collect the most compelling samples for this purpose.
The significance of this discovery extends beyond Mars itself. Rocks from this early period in planetary history are exceptionally rare on Earth, having been largely destroyed or altered by plate tectonics, erosion, and other geological processes. “By looking at the subsurface of Mars and understanding its geological history, we gain a better understanding of that time in the solar system when Earth transitioned from a molten world to more temperate temperatures,” Cardarelli explained.
What’s Next for Perseverance?
This study is based on data collected during 78 rover traverses, covering approximately six kilometers of terrain. However, Perseverance has already traveled around 40 kilometers since landing in February 2021, meaning a wealth of additional data is yet to be analyzed. “We’ve found so much more than we expected,” Cardarelli said, adding that her colleagues are already working on further scientific papers using the RIMFAX data. “I think there are going to be some new insights coming our way in the near future.”
The ongoing exploration of Jezero Crater by Perseverance continues to reshape our understanding of Mars’s past and its potential to have once harbored life. The rover’s continued journey and the eventual return of collected samples to Earth promise to unlock even more secrets of the Red Planet. The next major milestone will be the selection of the most promising samples for the Mars Sample Return campaign, a joint effort between NASA and the European Space Agency, currently planned for the early 2030s.
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