Recent explosive lava-water interaction in Tharsis, Mars.

The spatiotemporal distribution of water on Mars is fundamental to understanding the planet's evolution. Comprehensive integration and analysis of high-resolution remotely sensed datasets have enabled the investigation of previously uninterpreted small-scale volcanic landforms that imply the involvement of water during formation. Although volcanism has played a dominant role in shaping the Martian surface, irrespective of the physical state of water, there is little evidence of magma-water or lava-water interactions, especially in young, late Amazonian-aged volcanic provinces. Here, by combining surface imagery with topographic data and spectral analyses, we report the presence of rootless volcanic cones formed by explosive lava-water interaction during the late Amazonian (<215 Ma). They are found adjacent to Ascraeus Mons in Tharsis and are associated with spectrally identified hydrated minerals, most likely sulfates, indicating past hydrothermal circulation potentially sustained by lava-water interactions. We contend that these young, small landforms, formed through phreatomagmatic eruptions, can help reconstruct Martian paleoclimate, identifying water ice zones, and should be considered prime targets in the future search for life, as they fulfill key habitability criteria.