An international team of researchers led by scientists from the University of California at Los Angeles (UCLA) has revealed that new scans by the RIMFAX ground-penetrating radar system aboard NASA’s Mars Perseverance Rover discovered evidence of an ancient Martian river and other waterway structures near Jezero Crater.
The research team behind the discovery said the ancient river and deltaic structures, which formed around 4.2 billion years ago, could provide fresh insights into the red planet’s watery ancient history. The discovery could also support efforts to search for signs of ancient extraterrestrial life hidden beneath the planet’s surface.
“From the stratigraphic features mapped by RIMFAX, we can conclude that Jezero crater hosted an aqueous, possibly habitable environment capable of biosignature preservation, prior to the formation of Jezero’s Western Delta,” the researchers write.
Ancient Martian River Among Several Historic Perseverance Discoveries
When NASA’s Perseverance rover first touched down on February 18, 2021, its primary mission included searching for signs of ancient microbial life. However, the nuclear-powered vehicle was also tasked with verifying previous studies suggesting that Mars was once much wetter than it is today.
While a sample-return mission is still needed to determine whether Perseverance’s primary life-hunting mission was successful, the rover has found several pieces of compelling evidence that further bolster the case for a wet ancient Mars, including surface rivers and lakes that may have supported Martian lifeforms.
“The surface of Mars hosts widespread evidence of ancient flowing water and paleolakes,” the research team explained, adding that orbital and in situ spacecraft observations have also confirmed the presence of ‘aqueous alteration minerals’ on the planet’s surface.
Still, the initial scans indicating the presence of ancient waterways only penetrated a few inches beneath the Martian surface, limiting the amount of dispositive data that could be collected from them. Now, the rover has performed a new set of ground-penetrating radar scans that provide further support for the presence of an ancient river near Jezero crater.
Scans reveal numerous subsurface features consistent with an ancient river
According to a statement announcing the discovery, the study’s leader, UCLA’s Emily Cardarelli, focused on scans detailing features found in a currently submerged sedimentary deposit called the Margin unit. Because this region is rich in magnesium carbonates, the study authors said the site preserves a record of the planet’s ancient, wet climate.
“We analyze the depositional setting of the Margin unit, a major magnesium-carbonate deposit near the fluvial inlet to Jezero crater using ground penetrating radar data collected by the Mars 2020 Perseverance Rover Radar Imager for Mars Subsurface Experiment (RIMFAX) instrument,” they write.
Along with its mineral composition, the Margin unit site was chosen because previous studies had revealed features “indicative of paleolakes and river deltas.” This includes a prominent feature that appears to have been shaped by flowing water, called the Western Delta.
Unlike earlier scans, the researchers said the RIMFAX ground-penetrating scans reached depths of “greater than 35 meters.” For comparison, the team notes that this is approximately 1.75 times as deep as “other Jezero geologic units explored to date.” The team also noted that the new scans were collected during an “approximately 6.1-km rover traverse.”
After examining the new scans, the researchers discovered “numerous subsurface features” consistent with an ancient river. These features were revealed by scans taken at “submeter to hundred-meter scale layering,” offering a small- and large-scale view of the ancient Martian river. The team said they inferred that the features they located “are consistent with buried fluvial features and deltaic foresets, which have experienced multiple erosional-depositional episodes.”
“This work illuminates a well-preserved paleolandscape wherein a deltaic environment developed prior to the formation of the Jezero Western Delta, as early as the Noachian (~4.2 to 3.7 billion years ago),” they explained
Discovery “Improves the Chances of Finding Evidence for Past Life”
When discussing potential implications of an ancient Martian river delta hidden beneath the red planet’s surface, the team noted that the ground penetrating power of RIMFAX provided them with “a unique perspective into the shallow Martian subsurface.
The team also noted the work “may have implications for the preservation of potential biosignatures and habitability in the subsurface of Jezero crater,” by providing a potential window into habitable conditions on Mars. This includes widening the window of opportunity for ancient Martian lifeforms to take hold.
“RIMFAX has revealed an earlier subsurface deltaic environment under the present-day delta, thereby extending the period of potential habitability for Jezero back further in time,” the study authors explained. “This work also improves the chances of finding evidence for past life.”
The study “Ground penetrating radar observations of ancient large-scale deltaic structures in Jezero crater, Mars” was published in Science Advances.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.