New Mars Theory Questions Red Planet's Watery Past

New research suggests that magma could form some of these slick deposits rapidly, and ancient Mars may not have been as wet as we thought.

This image shows magma-spawned clay particles covering unaltered crystals in a basaltic lava flow from Mururoa seamount, French Polynesia. Similar structers on Mars cast doubt on its wet past, scientists say.
CREDIT: Meunier-Riffaut

In the past decade, astronomers have observed clay materials on Mars that seem to indicate large bodies of water once filled the Martian surface. But new research suggests that magma could form some of these slick deposits rapidly, and ancient Mars may not have been as wet as we thought.

A region of French Polynesia has similar deposits of these strange clays, which scientists found were formed by cooling magma rather than water.

"It was the first time that clays were shown to originate from another process than aqueous alteration," researcher Alain Meunier, of the Université de Poitiers in France, told by email. "The consequence was that, even if clays need water to be formed, this does not mean that they need liquid water."

Since water is thought to be essential for all life, the Martian clay findings complicate the question of whether early Mars was likely to have been hospitable to life. [Photos: The Search for Water on Mars]

Water vs. magma

Along riverbeds, near glaciers, and near oceans, clays on Earth tend to appear near sources of water. Layers of rock gradually weather away, their chemicals transported and mixing to form clay. The process takes time, and so the presence of clays on Mars would seem to indicate relatively long-standing bodies of water, such as oceans, lakes, and streams.

But four years ago, Meunier, working with a group of geologists, found that clays at the Moruroa Atoll in French Polynesia formed quickly with cooling magma rather than slowly with cold ocean water. As the magma cooled, small voids inside of the solidifying lava behaved as tiny pressure-cookers, forming the last generation of minerals, including clays. The iron-rich clays found at this Pacific Ocean atoll are similar in composition to some Martian mineral mixes.

The only samples on Earth that originated on the Martian surface come from rocks blown from the Red Planet long ago that traveled through space to our world. One such sample is the Lafayette Meteorite, a rock of unknown origin that was found in the archives of Purdue University and not identified as of Martian origin until 1931. Studying the meteorite with an eye toward the formation processes at Moruroa, Meunier's team, which included several geologists from the French-Polynesian group, found a number of similarities.

"The authors demonstrate pretty convincing evidence that some of the water that led to clay formation was derived from the magmatic gases," Brian Hynek of the University of Colorado told Hynek, who was not involved in the research, wrote a commentary piece that appeared alongside the results, which were published in the journal Nature Geoscience on Sunday (Sept. 9).

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