The Mars Rover Curiosity has recently discovered rocks that have far higher concentrations of silica than any it had analyzed since originally landing on the Red Planet more than three years ago, and now NASA is trying to find out what’s behind this unusual phenomenon.
According to the US space agency’s Jet Propulsion Laboratory in California, which announced the discovery of the silica-rich rocks Thursday in a statement, this combination of the elements silicon and oxygen makes up nearly 90 percent of the composition of some of the rocks.
While silica is common in quartz and other elements on Earth, on Mars rocks this rich in silica are “a puzzle,” according to Albert Yen, a member of the Curiosity science team at JPL. “You can boost the concentration of silica either by leaching away other ingredients while leaving the silica behind, or by bringing in silica from somewhere else.”
However, both processes “involve water,” he added. In one, acidic water would remove other substances and leave silica behind. In the other, neural or alkaline water transports silica that has already been dissolved and leaves it behind. If the JPL team can figure out which happened, Yen said, “we’ll learn more about other conditions in those ancient wet environments.”
What could have caused a rare mineral called tridymite to form?
Making things a little more complicated is a previous discovery by the Spirit rover, which found signs of sulfuric acid at a different location on Mars, and the fact that some of the silica detected by Curiosity is in the form of a mineral called tridymite. Tridymite is rare on Earth and had never been seen on Mars before, yet it was found by the rover at a site called “Buckskin.”
On Earth, tridymite is typically formed in igneous or metamorphic rocks exposed to extreme heat but the rocks analyzed by Curiosity have been interpreted as lakebed deposits. Also, tridymite is typically found in volcanic deposits rich in silica, but rocks found on the surface of Mars tend to have lower amounts of the substance. NASA believes that the discovery of the mineral could be evidence that magmatic evolution could be taking place on the Red Planet.
The discovery of these rocks have come over the last seven months, as the rover studies the area known as Mount Sharp. Specifically, its Chemistry and Camera (ChemCam) instrument fired its laser and detected an abundance of the element in some targets it traveled over en route to a part of the formation known as Marias Pass.
Jens Frydenvang from Los Alamos National Laboratory in New Mexico and the University of Copenhagen, Denmark, called the high silica content “a surprise” and said that the team was so stunned by the discovery that they “backtracked to investigate it” using the Alpha Particle X-ray Spectrometer (APXS) and the Chemistry and Mineralogy (CheMin) instruments.
Currently, the Curiosity team is trying to explain how the tridymite may have formed. “We could solve this by determining whether trydymite in the sediment comes from a volcanic source or has another origin,” said Liz Rampe of Aerodyne Industries at the Johnson Space Center. “A lot of us are in our labs trying to see if there’s a way to make tridymite without such a high temperature.”
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Image credit: NASA JPL
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