Rosalind Franklin Astrobiology Rover May Find Martian Biosignatures Uncovered By Rockfalls And Ancient Floods

The Rosalind Franklin mission’s chance of finding evidence of past life on Mars has been boosted by two studies that show that the rover won’t have to travel far to find materials potentially laden with organic molecules. Instead, natural processes could bring those materials to the rover, as revealed in two separate presentations at the EPSC–DPS2025 Joint Meeting in Helsinki this week.

Rosalind Franklin is a European Space Agency (ESA) mission currently scheduled to blast off to Mars in 2028. The rover will land in Oxia Planum, which is a large plain rich in clay minerals that formed in water billions of years ago.

The first study presented at EPSC–DPS2025, by Dr Aleksandra Sokołowska of Brown University in the USA and Imperial College London, describes how the identification of 258 rockfalls in the region of the landing site provides the opportunity for the rover to explore previously inaccessible material.

The second study, presented by Ananya Srivastava of the University of Western Ontario in Canada, reveals how organic-rich clays in Oxia Planum may have originated from elsewhere on Mars and been deposited through a series of floods over 3.5 billion years ago.

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Identifying the rockfalls at Oxia Planum requires the highest resolution imagery from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter, which can resolve objects as small as one metre. Many of the boulders brought to the ground by rockfalls are smaller than 2.5 metres and the largest is up to eight metres across. What really gives them away are their tracks, which can be metres deep and run for 500 metres.

Sokołowska and her colleagues identified the rockfalls at 48 sites thanks to a semi-automatic process, with deep-learning algorithms spotting candidate rockfalls that were then followed-up by a human being for verification. Most rockfalls were found on the steep slopes of craters, mounds and cliffs.

“We have reasons to believe that fresh rockfalls could be very common,” said Sokołowska. “More rockfalls are likely waiting to be found, as our manual follow-ups on small areas revealed many more than our semi-automatic search over the whole Oxia Planum region.”

The chance of Rosalind Franklin finding itself in the path of an onrushing rockfall is slim. Instead, the rover will be able to use them to its advantage.

Image from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter showing rockfalls and their trails in the Oxia Planum region. Image credit: Aleksandra Sokołowska (Imperial College)/NASA/HiRISE/University of Arizona. larger image

“The discovery of rockfalls in Oxia Planum opens up the exciting possibility for the rover to increase the diversity of its samples with material that would otherwise be inaccessible,” said Sokołowska.

Fragments of rock that had been embedded on slopes of mounds, crater walls and other steep cliff-faces before falling would have been partly shielded from the radiation that drenches Mars from space. This, in theory, will improve the chances of organic molecules surviving intact in them. The dirt displaced from metres below the surface by the tracks gouged out by the rockfalls could also provide a new source of accessible samples for the rover to examine.

Sokołowska’s work shows that impact craters play an important role in creating the conditions for the rockfalls, in terms of fracturing the ground and distributing loose material on slopes. She further explains that “Other factors that contributed to the development of rockfalls could include thermal stresses or early fluvial erosion, but a tectonic origin seems unlikely.

The impacts themselves do not necessarily trigger the rockfalls, however. “In terms of triggers, we found no link with recent marsquakes or new impact craters,” said Sokołowska.

Martian clays reveal episodic flooding on ancient Mars

Image from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter showing rockfalls and their trails in the Oxia Planum region. Image credit: Aleksandra Sokołowska (Imperial College)/NASA/HiRISE/University of Arizona. larger image

Clays are a prime target for Rosalind Franklin because they can preserve organic molecules, many of which are precursors to the building blocks of life. The clay-bearing geological units in Oxia Planum have compositionally different lower and upper sections (presented in false-colour infrared maps as orange and blue, respectively). It was previously suggested that these represent a single extensive clay unit, with an orange unit at the base overlain by a blue one, consistent with an in-situ formation of the clays.

Srivastava and her team studied clay units exposed in crater walls and found that, throughout Oxia Planum, there are multiple layers of alternating orange and blue sections. Furthermore, by comparing compositional data from NASA’s Mars Reconnaissance Orbiter (MRO) and ESA’s Mars Express missions with high-resolution imagery from MRO and ESA’s Trace Gas Orbiter, Srivastava’s team found a pattern. Craters at lower elevations tend to have thicker orange and blue layers than those at higher elevations, and overall the average thickness of these layers increases downslope of ancient highlands to the north-west of Oxia Planum.

An image of a crater in Oxia Planum, presented in false colour from the HiRISE camera on the Mars Reconnaissance Orbiter. The blue and oranges sections show multiple layers of clay units deposited in Oxia Planum and revealed at the crater wall. Image credit: Ananya Srivastava (University of Western Ontario) /NASA/HiRISE/University of Arizona. Larger image

“These results, particularly the variation in the layer thickness, imply that the clays may have originated elsewhere before being transported and deposited in the Oxia basin,” said Srivastava.

The clays were likely brought to Oxia Planum by rivers running from the highlands, the dried-out valley networks of which are still visible. The multiple layers indicate that there may have been cyclical or transient bursts of water that spilled into Oxia Planum about 3.5 billion years ago, before Mars completely lost its liquid water. The repeated clay-bearing layers may therefore be a signature of Mars’s ancient climate and geological conditions, offering clues as to how Mars evolved early in its history.

“The clays could record a far wider range of ancient Martian climatic conditions than previously believed if they came in multiple pulses from various source regions,” said Srivastava. “This diversity of environments improves the prospect that organic molecules were preserved under favourable conditions, strengthening the chances of uncovering the most thrilling discovery – clues for life beyond Earth.”

Further information

Aleksandra Sokołowska, Ingrid Daubar, Ariyana Bonab, Ian Haut, Valentin Bickel, Peter Fawdon, Peter Grindrod, and Susan Conway, https://doi.org/10.5194/epsc-dps2025-1727

Paper: Sokołowska, A. J., Daubar, I. J., Bonab, A., et al, ‘Fresh Rockfalls Near the Landing Site of ExoMars Rosalind Franklin Rover: Drivers, Trafficability and Implications’, npj Space Exploration, 1, 5 (2025) https://doi.org/10.1038/s44453-025-00008-7

This work was funded by the NASA MDAP grant #80NSSC22K1086.

Ananya Srivastava, Livio Tornabene, Gordon Osinski, Christy Caudill, Vidhya Ganesh Rangarajan, Peter Fawdon, Joe McNeil, Peter Grindrod, Ernst Hauber, Joel Davis, and Maurizio Pajola, https://doi.org/10.5194/epsc-dps2025-1001

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