Clay, Water and the Search for Life: Why ESA’s Rosalind Franklin Rover Is Targeting Mars’ Ancient Seabed
Date: 2026-07-10
Featured image: Artist’s illustration of the Rosalind Franklin rover on the Martian surface. Credit: ESA/ATG medialab
ESA’s ExoMars Rosalind Franklin rover is zeroing in on a 2028 launch to Oxia Planum, a clay-rich basin on Mars that new research shows is far more extensive than previously thought. A study published June 2 in the journal Icarus reveals that the clay deposits stretch approximately 300 kilometers (186 miles) from the planned landing site to the Mawrth Vallis valley, covering a region roughly 600 kilometers across and rising over 1 kilometer in altitude. The finding strengthens the case that this region was once covered by a vast body of water, potentially a deep ocean, and could preserve biosignatures of ancient microbial life.
The Rosalind Franklin rover, named after the British chemist who pioneered DNA crystallography, is Europe’s most ambitious Mars mission. At 310 kilograms (680 pounds) and roughly the size of a small car, it carries eight scientific instruments collectively known as the “Pasteur payload.” Its most distinctive feature is a 2-meter (6.6-foot) drill, the deepest ever sent to Mars, designed to access subsurface samples shielded from the harsh ionizing radiation that bombards the planet’s surface.
That depth matters. Cosmic radiation breaks down organic molecules in the top few centimeters of Martian soil, meaning any evidence of ancient life would most likely be found underground. The Viking landers in the 1970s managed only about 15 centimeters of penetration. The Rosalind Franklin’s drill reaches more than ten times that depth, opening access to material that has been protected for billions of years.
A water world, 4 billion years ago
The new Icarus study, led by Inés Torres Auré of the University of Lyon, used data from ESA’s Mars Express orbiter and NASA’s Mars Reconnaissance Orbiter to map the mineral composition and layering between Oxia Planum and Mawrth Vallis. Both sites share similar clay mineral sequences, indicating they were shaped by the same large-scale aqueous processes around 3.9 billion years ago.
The researchers identified a “paleosurface” at the boundary between two clay-bearing units, heavily cratered and later covered by younger deposits. This suggests a pause in sedimentation followed by a shift in water chemistry, pointing to an intermittently wet climate on early Mars rather than a single continuous wet period.
“Because the area is so large, we are not talking about a localized occurrence, but rather a regional or global process that would have required immense amounts of water,” said Jorge Vago, ExoMars project scientist, in an ESA statement. “We are targeting the oldest deposits in the sequence, which makes the potential implications for the geology and early climate of Mars very relevant for the Rosalind Franklin mission in its search for life.”
A rover built for biosignatures
The Rosalind Franklin rover was originally scheduled to launch in 2022 as part of a joint ESA-Roscosmos mission, with a Russian-built landing platform and a European rover. Following Russia’s invasion of Ukraine in February 2022, ESA terminated cooperation with Roscosmos. The mission was redesigned with a European-built lander and NASA providing the launch service, descent engines, radioisotope heating units, and components for the Mars Organic Molecule Analyzer (MOMA).
The rover is now targeting an October 2028 launch aboard a SpaceX Falcon Heavy from Kennedy Space Center’s Launch Complex 39A. The landing date is approximately November 2030, with a delayed trajectory chosen to arrive during northern spring and avoid planet-wide dust storms. A 2030 launch window is also available as a backup.
The Pasteur payload includes Panoramic Camera (PanCam) for geological context and 19-color spectral imaging; the Enfys infrared spectrometer for mineral composition; MOMA for broad-spectrum organic molecule detection using laser desorption and gas chromatography-mass spectrometry; MicrOmega for infrared hyperspectral microscopy; and the Raman Laser Spectrometer for identifying mineral phases and potential biosignatures. A ground-penetrating radar and the CLUPI close-up imager round out the suite.
Why clay?
Clay minerals, technically phyllosilicates, form in the presence of liquid water and are among the best preservers of organic molecules on Earth. The fine-grained structure of clay can encase organic compounds and protect them from chemical degradation over geological timescales. On Earth, clay-rich sediments routinely preserve evidence of ancient microbial life.
Oxia Planum specifically features Noachian-aged deposits, at least 3.7 billion years old, that formed in the presence of abundant liquid water. Two distinct aqueous environments have been identified: an early phase of deposition and alteration of layered clay-rich sediments roughly 100 meters thick, and a later fluvio-deltaic system. Erosion has exposed ancient sedimentary rocks whose surfaces have only recently been exposed to cosmic radiation, improving the chances that organics remain intact.
Elliot Sefton-Nash, ExoMars deputy project scientist, put it plainly: “We will use the instruments on board to ground truth the discoveries made from orbit, learn about the ancient environment in which they formed, and if they preserve any evidence of Martian life. Warmth and nutrients on an early martian seabed could have provided habitats for early life.”
The mission joins a broader push to answer the fundamental question of whether life ever arose beyond Earth. NASA’s Perseverance rover, currently exploring Jezero Crater, collected what scientists described in September 2025 as the strongest potential biosignature yet found at a site called “Cheyava Falls”: an arrowhead-shaped rock rich in organic carbon, sulfur, iron, and phosphorus. The two missions, one American and one European, are approaching the problem from opposite sides of the planet with complementary tools.
If the Rosalind Franklin rover launches as planned in 2028, it will be the first Mars mission to send a drill deep enough to access the subsurface radiation shield. Whether it finds ancient life or not, the science team expects to rewrite the story of how water shaped the Red Planet’s early history.
Draft for 1ban.news – Space Desk