Scientists have a fairly good idea of what Mars’ surface looks like. But exactly what that surface is made up of is more of a mystery. 

Now, scientists believe they have discovered an entirely new mineral on Mars from an unusual layer of iron sulfate with a distinct spectral signature. In a Nature Communications paper published on August 5, astrobiologists led by Janice Bishop at the SETI Institute describe the discovery of an unusual ferric hydroxysulfate compound around Valles Marineris, a vast chasm that sits along Mars’ equator. It’s an area that researchers suspect once flowed with water, and the new mineral’s discovery could offer tantalizing clues as to how and what natural forces sculpted the planet’s surface—and whether life once thrived on Mars. 

Sulfur, an element common to both Mars and Earth, often combines with other elements to form minerals in the form of sulfates. These minerals dissolve easily in water, but unlike Earth, Mars has persistently dry weather, meaning that sulfates may have remained on the surface since the planet lost its water. Studying these minerals, therefore, would uncover important information about Mars’ early history.

The researchers investigated sulfate-rich areas near Valles Marineris, paying special attention to regions that “included mysterious spectral bands seen from orbital data, as well as layered sulfates and intriguing geology,” explained Bishop in a statement. 

In one area, they found layered deposits of polyhydrated sulfates, with monohydrated and ferric hydroxysulfates underneath.

They tried to recreate these in the lab, finding that the ferric hydroxysulfate seen on Mars could only have formed in the presence of oxygen and that the reaction needed to produce the compound produces water. Further, this could only have happened at high temperatures, the researchers said, suggesting the sulfates formed from volcanic activity. What’s more, its structure and thermal properties suggest it is a totally new mineral.

“The material formed in these lab experiments is likely a new mineral due to its unique crystal structure and thermal stability,” Bishop said. “However, scientists must also find it on Earth to officially recognize it as a new mineral.”