The mysterious discovery of a concentrated piece of the rare mineral quartz in the Gale Crater region of Mars by the Curiosity rover in 2016 was finally explained by researchers.
A team of planetary scientists from Rice University, NASA’s Johnson Space Center, and the California Institute of Technology (CalTech) believe that the concentrated portion of tridymite was spewed into Gale Crater by a volcano when it was still filled with water until 1 billion years ago.
The new scenario suggests that the Red Planet has a much more interesting and complex volcanic history than previously thought.
Related: Rock samples from NASA’s Curiosity Mars probe contain a key ingredient for life
Tridymite, which is extremely rare on Earth, is a type of quartz — a form of silica — that is created under extreme temperatures and low pressures, and how it reached the bottom of an ancient lake has troubled researchers for years.
“The 3D discovery in a mudstone at Gale Crater is one of the most surprising observations Curiosity has made in its 10 years of Mars exploration,” said Rice University professor and team member Kirsten Seebach. statement (Opens in a new tab). “Tridymite is usually associated with advanced, explosive volcanic systems composed of quartz on Earth, but we found it at the bottom of an ancient lake on Mars, where most volcanoes are very primitive.”
To solve this mystery, Seebach and her colleagues looked at data on three-dimensional formation on Earth. They also looked at models of volcanoes on the Red Planet, its volcanic material, as well as sedimentary evidence collected from Gale Crater where Curiosity landed in August 2012.
This allowed them to devise a new scenario indicating that Martian magma stayed longer than usual in a chamber below the volcano. This allowed it to cool at least partially – a process called microcrystallization (Opens in a new tab) – It boosted the concentration of silicon in the magma.
Then a massive eruption released ash containing this extra silicon in a 3D form into the lake that would eventually become Gale Crater, as well as the surrounding rivers. This volcanic ash was then broken down by the water in the ancient lake which also helped to sort out the minerals in the ash.
This would have focused on 3D making consistent with Curiosity’s 2016 discovery. The researchers’ scenario would also help explain other aspects of the sample such as opaline silicate and its lower concentrations of aluminum oxide.
“It’s actually a direct evolution of other igneous rocks that we found in the crater,” Sebach said. “We argue that because we only saw this mineral once, and it was highly concentrated in one layer, it is possible that the volcano erupted at the same time the lake was there. Although the specific sample we analyzed was not exclusively volcanic ash However, it was ashes that were weathered and sorted by water.”
The findings also have broader implications for the geological history of Mars. This means that the Red Planet must have undergone intense and explosive volcanic activity more than 3 billion years ago. This could have been at a time when Mars was changing from a humid, warm world to the dry, arid planet we know today.
“There is plenty of evidence for basaltic volcanic eruptions on Mars, but this is a much more sophisticated chemistry,” Sebach concluded. “This work suggests that Mars may have a much more complex and interesting volcanic history than we imagined before Curiosity.”
The team’s findings were published in the journal Earth and Planetary Science Letters. (Opens in a new tab)
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