Clay Deposits Don’t Prove Existence of Ancient Martian Lakes

HiRISE image of branching features in the floor of Antoniadi Crater thought to contain clay material. (NASA/JPL/University of Arizona)

In the hunt for evidence of a warmer, wetter past on Mars, clay deposits have been viewed as good indications that stable liquid water existed on its surface for some time — perhaps even long enough to allow life to develop. But new research conducted here on Earth shows that some clays don’t necessarily need lakes of liquid water to form. Instead they can be the result of volcanic activity, which is not nearly so hospitable to life.

A research team led by Alain Meunier of the Université de Poitiers in France studied lavas containing iron and magnesium — similar to ancient clays identified on the surface of Mars — in the French Polynesian atoll of Moruroa. The team’s findings show that the same types of clay outcrops can be caused by the solidifying of water-rich magma in a volcanic environment, and don’t require Earthlike aquatic conditions at all.

The results also correlate to the deuterium-to-hydrogen (D/H) ratio within clays found in Martian meteorites.

Read: Life from Mars Could Have Polluted Earth

“To crystallize, clays need water but not necessarily liquid water,” said Alain Meunier to the Agençe France-Presse (AFP). “Consequently, they cannot be used to prove that the planet was habitable or not during its early history.”

Additionally, the clay deposits found on Mars can be several hundred meters thick, which seems to be more indicative of upwelling magma than interactions with water.

“[This] new hypothesis proposes that the minerals instead formed during brief periods of magmatic degassing, diminishing the prospects for signs of life in these settings,” wrote Brian Hynek from the Department of Geological Sciences at the University of Colorado, in response to the paper by Meunier et al. which was published in the September 9 edition of the journal Nature Geoscience.

This does not necessarily mean that all Martian clays weren’t formed in the presence of water, however. Gale Crater — where NASA’s Curiosity rover is now exploring — could very well have been the site of a Martian lake, billions of years in the past. Clays found there could have been created by water.

Read: Take a Trip to Explore Gale Crater

According to Bethany Ehlmann of the California Institute of Technology, co-author of the study, “there are particular characteristics of texture” to clays formed under different conditions, and “Gale is a different flavor of Mars.”

Perhaps Curiosity will yet discover if Gale’s original flavor was more cool and wet than hot and spicy.

Read more on New Scientist and Cosmos Magazine.

Inset image: Moruroa Atoll (NASA)