Scientists have finally found the answer to how one of the rarest minerals around came to be found in a crater on Mars. Since NASA's Curiosity rover discovered the mineral, tridymite, in the Martian Gale Crater in 2016, scientists have wondered how this form of quartz, which is extremely rare on Earth, was found on the Red Planet. The answer is volcanic activity that happened billions of years ago.
"The discovery of tridymite in a mudstone in Gale Crater is one of the most surprising observations that the Curiosity rover has made in 10 years of exploring Mars," said Rice's Kirsten Siebach, co-author of the study behind the revelation published in the journal, Earth and Planetary Science Letters.
Tridymite is formed only in high-temperature, low-pressure conditions on Earth, commonly associated with volcanic eruptions. "Tridymite is usually associated with quartz-forming, explosive, evolved volcanic systems on Earth, but we found it in the bottom of an ancient lake on Mars, where most of the volcanoes are very primitive,” Siebach stated.
The team of researchers examined volcanic data from models of Mars volcanism as well as sedimentary evidence from Gale Crater, which was a lake about one billion years ago as evidenced by Curiosity. Using data from reported instances of the mineral on Earth, the team of researchers came to the conclusion that matched all the evidence.
The team believes that the magma underneath the volcano underwent a process of partial cooling called fractional crystallisation, while it waited longer than usual for an eruption.
The magma, in the process, collected additional silicon which was then spewed outwards into the lake into a massive eruption. This helped create the tridymite while the water in the lake cleared the ash around the mineral through chemical weathering. The scenario also explains other geological evidence found by the Curiosity rover, like the presence of opaline silicates and reduced concentrations of aluminium oxide.
Siebach explained that it’s actually a straightforward evolution of volcanic rocks found in the crater. “We argue that because we only saw this mineral once, and it was highly concentrated in a single layer, the volcano probably erupted at the same time the lake was there,” the author said.
This finding suggests that Martian volcanic history is more complex than previously thought.
