Granite has always been thought of as an igneous rock commonly found on Earth, but new research suggests it could be present on Mars as well.
A mineral called feldspar was discovered in a Martian volcano, and the substance is commonly found in granite, a Georgia Institute of Technology news release reported.
The finding would makes senses, since Earthly granite is commonly found in areas with volcanic activity, the team concluded "prolonged magmatic activity" could cause the same effect on the red planet.
"We're providing the most compelling evidence to date that Mars has granitic rocks," James Wray, an assistant professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology and the study's lead author, said.
In the past, researchers believed Mars was a simple planet that consisted of mostly basalt, which is a dark volcanic rock which can be found on Earth in regions like Hawaii. This year NASA's Curiosity rover may have debunked that theory when it found soil with a similar composition to granite; which is an igneous rock that is light in color.
The research team used "remote sensing techniques with infrared spectroscopy" to confirm Curiosity's findings. The looked at an ancient volcano that had not been active for billions of years and was "dust-free," making it an ideal study subject. Most Martian volcanoes are doused in a thick layer of dust, but the team believes "fast-moving sand dunes" could be responsible for sweeping it off the ancient object.
"Using the kind of infrared spectroscopic technique we were using, you shouldn't really be able to detect feldspar minerals, unless there's really, really a lot of feldspar and very little of the dark minerals that you get in basalt," Wray said.
The team was surprised to detect the feldspar in the volcano, despite these circumstances.
Since there is very little dark mineral in the volcano (and plenty of feldspar) the idea that granite could form seems to pan out.
"While the magma slowly cools in the subsurface, low density melt separates from dense crystals in a process called fractionation," the news release reported.
If this cycle was repeated over billions of years, it could cause granite to slowly form; and computer simulations by Josef Dufek, who is also an associate professor in the School of Earth and Atmospheric Sciences at Georgia Tech supported this theory.
"We think some of the volcanoes on Mars were sporadically active for billions of years," Wray said. "It seems plausible that in a volcano you could get enough iterations of that reprocessing that you could form something like granite."
The process in question is called igneous distillation; which is an enrichment is silica melt that can cause a lower rock density. This low-density rock would have similar properties to granite.
These compositions are roughly similar to those comprising the plutons at Yosemite or erupting magmas at Mount St. Helens, and are dramatically different than the basalts that dominate the rest of the planet," Dufek said.
Past studies have found similar environmental compositions on other regions of Mars, but chalked it up to anorthosite; a substance commonly found on the Moon. The Georgia Tech team believe the presence of granite is more likely.
"We talk about water on Mars all the time, but the history of volcanism on Mars is another thing that we'd like to try to understand," Wray said. "What kinds of rocks have been forming over the planet's history? We thought that it was a pretty easy answer, but we're now joining the emerging chorus saying things may be a little bit more diverse on Mars, as they are on Earth."
