Scientists at NASA's Jet Propulsion Laboratory announced Tuesday that the Perseverance rover has detected strong radar signatures consistent with a liquid water reservoir approximately 1.5 kilometres beneath the Martian surface in the southern Hellas Planitia region — the most significant finding in the search for extraterrestrial habitability in over two decades.
The data, collected over fourteen months of systematic scanning, shows a bright reflective layer that matches the radar signature of liquid water as detected in analogous environments on Earth, including subglacial lakes in Antarctica. The reservoir is estimated to span approximately 40 kilometres across and could be several metres deep.
What keeps the water liquid at such depths — where surface temperatures average minus 60°C — remains an open question. Researchers hypothesise that residual geothermal heat from Mars' slowly cooling core, combined with the presence of dissolved salts acting as antifreeze, may maintain conditions suitable for liquid water year-round.
The finding does not confirm the presence of life, and scientists were careful to temper the announcement with appropriate caution. "We have found the conditions that, on Earth, we associate with microbial life," said Dr. Yuki Tanaka, NASA's astrobiology programme lead. "We have not found life. But the questions we're now asking are more interesting than ever."
A follow-up mission capable of drilling to the reservoir depth is not currently funded, but NASA sources indicated Tuesday that the discovery would "significantly strengthen" the case for a future dedicated astrobiology lander. The European Space Agency said it was "reviewing the implications" for its own Mars programme.