Planetary scientists examining MESSENGER spacecraft images have identified glacier-like flows inside Mercury’s Raditladi and Eminescu craters. Composed of salts and volatile-rich materials preserved for more than a billion years, these features suggest that the solar system’s innermost planet may harbor hidden, potentially habitable subsurface niches.
Salty Flows on the Solar System’s Scorchingly Hot Inner Planet
Mercury appears to be an unlikely location for glacial activity. Sunlit ground temperatures on the innermost planet can reach about 430°C, and the world possesses virtually no atmosphere to shield its surface from intense solar radiation. Yet, imaging data collected by NASA’s MESSENGER spacecraft reveal lobate runouts, flow fronts, and lineations clustered near the central peak rings of the Raditladi and Eminescu impact craters. These landforms closely resemble glacial features observed on Earth and Mars.
Rather than being composed of water ice, these formations are interpreted as flows dominated by salts and other volatile-rich materials excavated from deep within the planetary crust. Thermal and flow models indicate that such deposits could retain volatile compounds under a protective cover for more than a billion years. Raditladi itself carries a crater-count model age of roughly 1.1 billion years, providing compatible timelines for the structures.
Uncovering Subsurface Volatiles and Missing Crater Material
The discovery offers a compelling explanation for a long-standing geological mystery on Mercury: irregular, rimless depressions known as hollows that frequently feature bright, shallow pits. When large asteroids struck Mercury, the compressed planetary floors rebounded, lifting volatile-rich material from depth into central peak rings. Exposed on steep slopes, this material became mobile, deformed, and spread laterally before a less volatile crust eventually formed over it. The subsequent loss of exposed volatile components left behind hollows and a refractory residue.
Researchers investigating the findings emphasize that the discovery bridges terrestrial extremes with planetary science. Alexis Rodriguez, a planetary scientist at the Arizona-based Planetary Science Institute (PSI), noted the broader significance in a statement accompanying the study, which was published in The Planetary Science Journal.
Parallels to Earthly Extremophiles and the Search for Life
While Mercury’s salt flows bear little resemblance to traditional Arctic glaciers, geologists look to severe terrestrial environments for operational models. On Earth, specific salt compounds establish protective microenvironments capable of sustaining life in punishing landscapes like Chile’s arid Atacama Desert. This terrestrial analogy prompts researchers to consider whether Mercury might host hospitable subterranean zones sheltered from surface radiation.
Rodriguez added, This line of thinking leads us to ponder the possibility of subsurface areas on Mercury that might be more hospitable than its harsh surface.
Just as stellar systems possess habitable Goldilocks zones where liquid water can persist, the researchers suggest that Mercury might feature a subterranean, potentially habitable
region.
Unresolved Questions Surrounding Mercury’s Volatile Beginnings
A fundamental question remains regarding how these volatile layers accumulated on Mercury in the first place. Scientists have proposed multiple origin hypotheses. One possibility involves the collapse of a fleeting, hot primordial atmosphere during the planet’s early history.
These findings arrive as researchers continue to puzzle over Mercury’s bulk composition. Data from the MESSENGER mission previously showed that the planet holds unexpectedly high concentrations of moderately volatile elements like potassium, despite forming close to the Sun. According to Johannes Benkhoff, ESA BepiColombo Project Scientist, Potassium evaporates very quickly in a hot environment while thorium survives even in very high temperatures,
creating an elemental ratio that challenges existing planet formation models.
Further exploration rests on upcoming mission data. The European-Japanese BepiColombo mission, featuring instruments like the MERTIS Radiometer, the MIXS Imaging X-ray Spectrometer, and the MGNS Gamma-ray and Neutron Spectrometer, aims to provide high-resolution mapping and elemental analysis to determine how Mercury formed and whether water ice or volatile layers truly persist across its polar and equatorial extremes.
