The European Space Agency's Rosalind Franklin rover will touch down in one of Mars's most geologically significant locations. New orbital data reveals that its landing site at Oxia Planum sits within a clay-rich region spanning hundreds of kilometers across the Martian surface. This discovery transforms understanding of the planet's ancient hydrological past.
Clay minerals form in the presence of liquid water. Their widespread distribution at Oxia Planum indicates that a vast hydrothermal system once operated across this region of Mars billions of years ago. The rover's instruments will directly sample and analyze these clay deposits, providing the first ground-truth measurements of this enormous ancient aqueous environment.
Rosalind Franklin, part of ESA's ExoMars program, carries a drill capable of extracting samples from two meters below the Martian surface. This depth reaches material protected from cosmic radiation and UV exposure, preserving organic compounds that may have survived since Mars's early history. The rover's Pasteur instrument suite will analyze these samples for biosignatures. organic molecules, and mineral compositions that reveal the conditions under which water persisted on Mars.
The Oxia Planum region has long attracted rover planners. Located at approximately 18 degrees north latitude in Valles Marineris, the site shows stratigraphic layers deposited during Mars's Noachian epoch, roughly 4.1 to 3.7 billion years ago. Orbital spectroscopy by NASA's CRISM instrument and the Indian Space Research Organisation's Chandrayaan-1 previously identified clay-bearing deposits there. The new mapping confirms that these deposits extend far beyond the immediate landing zone.
This discovery reshapes the narrative of Martian water history. Scientists previously debated whether Mars experienced one major wet period early in its history or multiple episodic pulses of habitability. The scale of the clay-rich region suggests sustained, expansive water activity across a continental area. Such conditions would have created diverse ecological niches for potential microbial life, had life emerged on Mars.
The ExoMars mission launches from Earth in 2028, with arrival at Mars expected in 2030. The Rosalind Franklin rover and its companion Kazachok rover, supplied by Roscosmos, will deploy from the Kazachok platform. Roscosmos's participation in ExoMars continues despite geopolitical tensions, reflecting the scientific value both agencies place on this mission.
Understanding Oxia Planum's hydrothermal history informs astrobiology research beyond Mars. The types of mineral assemblages and water-rock interactions preserved here parallel processes that occur on Earth in deep subsurface environments where microbial life persists independently of sunlight. Finding evidence of similar chemistry on ancient Mars strengthens arguments that the planet once harbored habitable environments.
The timing of Rosalind Franklin's deployment arrives as Mars science shifts toward detailed paleoclimatology and the search for biosignatures. NASA's Perseverance rover currently investigates Jezero Crater's deltaic deposits. China's Zhurong rover explored Utopia Planitia's subsurface layers. ExoMars will contribute a third major perspective by analyzing protected subsurface samples in a clay-bearing region that records a different phase of Martian history.
These complementary missions build a comprehensive picture of Mars's transition from a potentially habitable world to the cold, dry desert it became. Rosalind Franklin's drill samples will bridge the gap between orbital spectroscopy and direct chemical analysis, confirming or revising current models of how Mars lost its atmosphere and water.