LOS ANGELES — A new theory is pouring some cold — actually, some really hot — water on the idea that Mars could have been habitable in the past.

Planetary scientists searching the Red Planet for places that could have contained the building blocks for life look for clues in clays, which can offer some indication that water flowed on or just under Mars’ surface. But a new study suggests that, at least in some cases, those clays might be a red herring.

A paper published online Sunday by the journal Nature Geoscience argues that such clays might have been formed in hot Martian magma rich in water. If so, that water would have been far too hot to support microbial life.

The argument contrasts with two more common theories, said study co-author Bethany Ehlmann, a planetary geologist at the California Institute of Technology. One of them is that liquid water flowing across the Martian surface would have interacted with surrounding minerals, forming the clays. In another scenario, underground water warmed by the planet’s internal heat could have provided a comfortable living environment before it got bound up in the mineral structure of clays.

On Earth, clays are remarkably good at trapping organic material. So if organic compounds existed on Mars, clays would be a good place to find them.

If either of the prevailing theories about water is true, the Martian environment could have been hospitable for life, Ehlmann said. Superheated water and magma? Not so much.

“The clays would form as the lava cools from 1,500 degrees Celsius,” she said. “That would not be a good habitat.”

The light signatures of these clays are very similar to some Martian deposits. And some — but not all — Martian meteorites collected on Earth appear to support the new theory, the study authors wrote.

It’s possible that all three models could be right, depending on where you’re looking, said Ralph Milliken, a planetary scientist at Brown University who was not involved in the study.

“It’s certainly a different take on trying to explain the origin of some clay minerals on Mars,” he said. “It does have some merit, and alternative hypotheses need to be considered fully.”