New York: Scientists at the US space agency NASA have discovered tridymite — an unexpected silica mineral in a rock sample at Gale Crater on Mars that may alter our understanding of how the Red Planet evolved.

NASA’s Mars Science Laboratory rover, Curiosity, has been exploring sedimentary rocks within Gale Crater since landing on Mars surface in August 2012.

On sol 1060 (the number of Martian days since landing), the rover collected powder drilled from rock at a location named “Buckskin”, NASA found in a study.

Scientists in the Astromaterials Research and Exploration Science (ARES) Division at NASA’s Johnson Space Centre in Houston led the study and the paper on the team’s findings was published in the Proceedings of the National Academy of Sciences.

The detection was a surprise to the scientists because tridymite is generally associated with silicic volcanism, which is known on Earth but was not thought to be important or even present on Mars.

Tridymite requires high temperatures and high silica concentrations to form, conditions which most typically are found in association with silicic volcanism.

“On Earth, tridymite is formed at high temperatures in an explosive process called silicic volcanism. Mount St. Helens, the active volcano in Washington State and the Satsuma-Iwojima volcano in Japan are examples of such volcanoes,” said Richard Morris, NASA planetary scientist at Johnson.

“The combination of high silica content and extremely high temperatures in the volcanoes creates tridymite. The tridymite was incorporated into ‘Lake Gale’ mudstone at Buckskin as sediment from erosion of silicic volcanic rocks,” Morris, who is also the lead author of the paper, added.

The discovery of tridymite might force scientists to rethink the volcanic history of Mars, suggesting that the planet once had explosive volcanoes that led to the presence of the mineral.

“I always tell fellow planetary scientists to expect the unexpected on Mars,” said Doug Ming, ARES chief scientist at Johnson and co-author of the paper.

“The discovery of tridymite was completely unexpected. This discovery now begs the question of whether Mars experienced a much more violent and explosive volcanic history during the early evolution of the planet than previously thought,” Ming added.