An article published in the journal “Proceedings of the National Academy of Sciences” (PNAS) describes the unexpected discovery of a mineral called tridymite by the Mars Rover Curiosity in Gale Crater on Mars. The analysis of a sample from a rock called Buckskin revealed the presence of tridymite, which on Earth forms as a result of much more intense volcanic activity than that assumed esisted in the past on Mars.

The Mars Rover Curiosity was in the area of Mount Sharp where the Buckskin rock is located almost a year ago. On Sol 1060 (the Martian day from from its landing), meaning at the end of July 2015, Curiosity drilled the rock to extract a sample as happened with many other rocks in the course of its mission but this time it found this unexpected compound.

Tridymite is the common name of silicon dioxide and on Earth it forms in an explosive way, during what is called silicic volcanism. The combination of a high presence of silica and very high temperatures creates tridymite. The sample of this mineral was on Mars in Gale Crater, in the mudstone of an ancient lake.

The ARES (Astromaterials Research and Exploration Science) division scientists led by Richard Morris who conducted this research tried to understand how tridymite can form in much less extreme conditions than those explosive of silicic volcanism but with no success. However, this doesn’t prove that a violent volcanic event is necessary to form tridymite but scientists are puzzled.

There is also the possibility that the volcanic phenomena of the past of Mars were more intense than scientists thought. In particular, it can be hypothesized that there were explosive volcanoes on the planet but since there is no proof that they’re necessary to form tridymite it’s likely that many more data are needed to understand its origin.

Doug Ming, chief scientist of the ARES division and one of the authors of the article, pointed out that he always says to his fellow planetary scientists to expect the unexpected on Mars. There are still many things we don’t know about the red planet and each new observation or analysis can bring new surprises.