A cataclysmic fusion born inside Martian volcanoes might have created an odd rock called “ignimbrite” that combines igneous and sedimentary rocks.
The peer-reviewed research suggests that olivine-rich rock spotted in Gusev Crater (by the now-concluded Spirit rover mission) and Jezero Crater (home of the Perseverance rover) might have arisen in huge volcanic calderas.
While how those rocks got there has been a debate for two decades, the new study says that olivine is commonly made within magma that originates from the mantle of Mars, just like on Earth. While at first they were testing a notion that ash coming from the plumes created the rocks, a library of images on Earth showed rocks that looked remarkably similar to those caught on Mars by the Spirit rover.
How those Earth rocks got there is truly spectacular. “Imagine a ground-hugging cloud of hot gases and nearly molten ash and pumice flowing through the landscape for dozens of miles and piling up in layers up to hundreds of feet thick in just a few days,” Steve Ruff, a planetary geologist at Arizona State University, said in a statement.
The rocks, known as ignimbrites, tend to cool over months or years and create fractures called “cooling joints”, caused by ash and pumice contracting. Ruff and the team saw fracture patterns that were similar on Mars to those images on Earth, in places like Yellowstone National Park.
“No one had previously suggested ignimbrites as an explanation for olivine-rich bedrock on Mars,” Ruff said. “And it’s possible that this is the kind of rock that the Perseverance rover has been driving around on and sampling for the past year.”
More analysis of local rocks will be helpful to fleshing out the hypothesis. While Spirit is long concluded, Perseverance might be able to do some work on site. Further in the future, NASA does plan a sample return mission of some of Perseverance’s rocks as soon as 2033, which may allow researchers to get more access with facilities on Earth.
A study based on the research was published in Icarus.