We can finally understand how a strange rare mineral appeared on Mars

(ORDO NEWS) — In 2016, the Curiosity rover discovered something really unusual in Gale Crater on Mars.

On the slope of Mount Sharp, where Curiosity worked, there was a large amount of a rare mineral; rare, at least here on Earth. Tridymite, a variety of quartz, seems to form extremely rarely and at high temperatures, similar to those found in magma.

While there is extensive evidence of past activity of basalt volcanism on Mars in some regions, the once supposedly water-filled Gale crater is not among these regions, leading scientists to wonder how the mineral ended up there. solve the mystery: this tridymite could have formed as a result of a single explosive volcanic eruption that occurred approximately 3.0 to 3.7 billion years ago.

“The discovery of tridymite in mudstone in Gale Crater is one of the most amazing sightings. what the Curiosity rover has done in 10 years of exploring Mars,” said Martian geologist Kirsten Siebach of Rice University.

“Tridymite is usually associated with quartz, explosive, evolved volcanic systems on Earth, but we found it at the bottom of an ancient lake on Mars, where most of the volcanoes are very primitive.”

Since we can’t really get to Mars, scientists had two tools to solve the mystery: the tridymite deposits found here on Earth, and the collected mineral samples. from Gale Crater and Mount Sharp – the peak at the center of the crater – by Curiosity, which sends data about its findings back to Earth.

That’s where Peyre, then at Rice University, and her colleagues turned to.

First, the Earth. Each documented deposit of tridymite and the conditions of its formation have been carefully studied by the research team.

They then sifted data collected by Curiosity on the composition of the lake’s long-dried sedimentary lakebed in Gale Crater.

Tridymite forms at temperatures above 870 degrees Celsius (1600 degrees Fahrenheit) and turns into a phase called cristobalite at about 1470 degrees Celsius. Both of these forms were found in the same layer on the slope of Mount Sharp.

In addition, Curiosity has discovered feldspar and opal silica, which on Earth can be found in volcanic contexts.

Putting these pieces together, we get an exciting scenario related to the magma chamber under Gale Crater that existed billions of years ago. The team surmised that this camera must have been underwater for a while longer than usual.

During this time, cooling should have resulted in a process called fractional crystallization, removing and separating minerals to produce excess silica.

When the chamber eventually exploded, it was the result of a massive explosion that sent silica-containing ash into the air now in the form of tridymite to rain down again into the lake at Gale Crater and its surrounding tributaries.

Those waters would have had to weather and sort out the ash to get the layer chemistry observed by Curiosity, the team said.

“This is actually a straight-line evolution of other volcanic rocks that we found in the crater,” Siebach explained.

“We argue that since we only saw this mineral once, and it was highly concentrated in one layer, the volcano probably erupted. at the same time, the lake was there. Although the particular sample we analyzed was not exclusively volcanic ash, it was ash weathered and sorted by water.”

Because this silica eruption is an evolved type that would be different from the basaltic volcanism evidence for which is abundant on Mars, the team’s analysis suggests that the red planet may have had a much more complex volcanic history than we know.

Future missions should look for evidence of other instances of this advanced volcanism to help limit when and in what context it happened on Mars, the team said.

“Mars,” they wrote in their article, “is not only a basalt world.”

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