Eight Hebrus Valles Caves May Have Been Carved by Water — Promising Targets in the Search for Life on Mars

Eight potential water‑carved caves discovered in Hebrus Valles

A team led by Shenzhen University reports eight cave entrances in Mars' Hebrus Valles that show multiple lines of evidence consistent with formation by flowing or standing water. The study, published in The Astrophysical Journal Letters, identifies these features as compelling candidates for future robotic and human exploration because caves on Mars could protect instruments and people from extreme cold, intense winds and high surface radiation.

What the researchers found

Using mineralogical maps and orbital imagery from NASA missions (Mars Global Surveyor and Mars Odyssey), the team identified sinkholes and collapse features whose shapes and surrounding deposits strongly suggest dissolution of water‑soluble rock. The orbital data show:

• Signatures of water‑soluble substrates and sulfates at several sinkhole sites.
• Elevated hydrogen concentrations detected at the same locations, consistent with past presence of water or hydrated minerals.
• Three‑dimensional sinkhole models derived from satellite imagery whose morphologies match collapse by dissolution rather than purely volcanic or tectonic processes.

'These skylights are interpreted as the first known potential karstic caves on Mars, representing collapse entrances formed through the dissolution of water‑soluble lithologies — defining a new cave‑forming class distinct from all previously reported volcanic and tectonic skylights.'

On Earth, karstic caves form where slightly acidic water dissolves soluble rocks (for example, limestone), producing underground voids and collapsed skylights. If similar processes occurred on Mars, the resulting caverns could preserve minerals, organics or biosignatures from wetter periods in the planet's history — or, less likely but still possible, shelter extant microbial life.

Why this matters

Caves provide natural shielding from the harsh surface environment, making them attractive targets both for astrobiology and for future human bases. The authors recommend prioritizing these Hebrus Valles sites for follow‑up observations and for missions capable of entering and sampling cave interiors, since remote orbital data alone cannot confirm life or past habitability.

While the evidence is strong and intriguing, it is still circumstantial: definitive answers require in situ exploration, direct sampling, and laboratory analysis. The discovery, if confirmed by follow‑up missions, would expand our understanding of cave formation on Mars and highlight promising locations in the ongoing search for past or present life.