Earlier this year, NASA’s Curiosity rover discovered felsic minerals on Mars. While minerals like feldspar and quartz make up the majority of Earth’s crust there has not been a lot of evidence to suggest that these minerals exist on Mars. This has exciting implications that the geology of Mars is much more complex than was previously known. The study was led by James Wray of the School of Earth and Atmospheric Sciences at Georgia Tech and was published in Nature Geoscience.
Mars doesn’t seem to have tectonic plates, meaning the planet’s crust does not undergo the same magmatic cycle as Earth to create minerals like feldspar. Most evidence to the contrary has likely been lost to erosion. Most of Mars is covered in basalt, a volcanic rock. This type of rock is called mafic, as it contains large amounts of magnesium and iron (“ferric” is used to describe iron-rich substances).
However, after Curiosity discovered the felsic minerals, scientists wanted to take another look. The Mars Reconnaissance Orbiter took near-infrared images of three completely different areas of the Martian surface. They were able to detect feldspar in a really ancient volcano, which means it had to exist in large enough quantities to be detected through the basalt.
Scientists reason that this could have come about in a process known as fractionation. The magma in the volcano is separated based on density when it cools. Over an extended period of time, it might not be such a stretch that something like granite could form this way.
Another paper published in the same journal argues that the feldspar from other areas on Mars is more indicative of anorthosite, not granite. Anorthosite is an igneous rock that is formed when mafic rocks, like what are commonly found on Mars, melt in the magma chambers in the crust. A liquid with a density greater than the magma separates out to cool on the crust. Small amounts of the liquid crystallize in the bottom of the chamber and is known as anorthosite. While there isn't currently a consensus about what the feldspar indicates, we now know that it is much more than a boring ball of basalt.
While much of the public’s interest in Mars has been focused on water content and possibility for life, there is a great deal of interest in the geology of Mars. The rocks can provide major information about what has happened to the planet’s surface in the 4 billion years since it was abundantly covered in water. Understanding the planet’s composition might help determine what astronauts will need when they are sent on missions to Mars.
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