As NASA's Curiosity rover scours the Martian surface in search of signs that Mars was once capable of fostering complex life, a team of researchers from the University of Poitiers, France, and Caltech have issued a paper that casts serious doubt on the notion that the planet was once habitable.
The new theory, which was published in Nature Geoscience, indicates that clay found on the Martian surface was formed in water-rich magma — water that would be way too hot to support life.
To make their case, a research team led by Alain Meunier studied clay minerals and rocks collected from an old A-bomb test site in French Polynesia. The geologists discovered that the clay minerals bore a remarkable resemblance to the ones observed on Mars. But unlike the South Pacific clays, which were products of weathering by liquid water, the ones on Mars were formed directly from water-rich molten rock as they cooled.
Reporting for the BBC, Jonathan Amos explains further:
It is interesting because it strikes at the heart of the notion that the Red Planet was awash with water, perhaps at its surface, more than 3.75 billion years ago - an idea that has been put forward to explain the great abundance of some clay deposits observed from orbit by satellites.
However, the process of clay production at Mururoa, if replicated and widespread on early Mars, would remove the need for such large volumes of water, and with it possibly a more benign environment for life to establish itself on the planet.
"Mars was not as warm and wet in its earliest time as some have suggested. I do not believe in an early ocean on Mars," Prof Meunier told BBC News.
But [The Mururoa process] explains only the earliest generation of clays on Mars, in the early Noachian period. In later periods, liquid water has existed on Mars' surface; that is undoubtedly the case."
And as the LA Times' Amina Khan notes, this has serious implications for Martian habitability:
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."
But as Khan notes, the study leaves a number of questions unanswered:
"It's certainly a different take on trying to explain the origin of some clay minerals on Mars," [said planetary scientist Ralph Milliken] "It does have some merit, and alternative hypotheses need to be considered fully."
But he said the story laid out in the new paper doesn't explain why the Martian surface appears to have tracks cut by flowing liquid. Nor does it account for blueberry-shaped mineral deposits of hematite that scientists believe may have formed when water ran past them.
Again, Meunier is not claiming that surface water has never existed on Mars — merely that it wasn't present during its early Noachian period (a time that might have been critical to the spawning of life). The jury, therefore, is still very much out on this one.
Read the entire paper here.
Other sources: BBC.
Top image: A three-dimensional image of the Nili Fossae region of Mars showing clays presence of abundant clays minerals (in magenta and blue hues) via NASA/JPL/JHUAPL.