Surface clay survey offers clues to early Martian climate

Feb. 6 (UPI) -- New analysis of Mars' abundant surface clays has offered fresh insights into the Red Planet's early climate.

Many geologic and chemical signatures suggest Mars was once wet and warm. But while water was once freely flowing, most models predict a cold climate on early Mars.

To better understand how Mars could assume the attributes of a wet, warm world under apparently cold conditions, scientists looked to the Red Planet's surface clays. Minerals found in clay deposits require warm temperatures to form.

"We realized that in order to better constrain the early Martian climate, we needed to understand the formation conditions of Martian clays," Janice Bishop, scientist at the SETI Institute and NASA's Ames Research Center, said in a news release.

Researchers began by mapping the three different types of clays found on Mars' surface. Magnesium-rich clays are formed beneath the surface at higher temperatures, between 100 and 400 degrees Celsius. Clays rich in iron or aluminum, including dioctahedral and smectite clays, are formed in aqueous environs -- lake, river and stream beds -- at temperatures between 20 and 50 degrees. Clays with poorly-formed crystals of aluminosilicate minerals are formed at temperatures below 20 degrees.

Their analysis showed smectite clay deposits, such as nontronite and montmorillonite, likely formed during short-term intervals of warmer temperatures.

Volcanism, axis tilt changes or large impacts could have inspired periods of slightly warmer temperatures, 10 to 15 degrees Celsius. These periods could have lasted several hundred thousand years. During these intervals, seasonal temperatures could briefly reach 25 to 40 degrees -- warm enough for significant clay formation.

An improved understanding of when and how Mars got its clay can help researchers determined when and where water was most likely present on early Mars, which can help scientists determine where to look for signs of life.

Bishop and her colleagues published their analysis this week in the journal Nature Astronomy.