As humans compete to become an interplanetary species, their first destination in cosmic neighborhood will be Mars. Land hikers prepare the foundation as they delve into the geological history of the Red Planet. Observations by two biologists on wheels point to the neighboring planet’s violent volcanic past.
A team of researchers from Arizona State University has identified Embrite, an igneous and sedimentary rock that forms as a result of catastrophic explosive eruptions from a supervolcanic caldera. The team analyzed data from two missions to Mars, and studied the mysterious, olive-rich bedrock in Josef Crater and in and around Jezero Crater, where the currently roaming probe is looking for signs of ancient microbial life.
The findings, published in the journal Icarus, indicate that the bedrock is being recognized as a potentially explosive volcanic deposit, but the nature of its eruption is poorly constrained, limiting understanding of what may have been a large-scale volcanic process on early Mars. “If true, this phenomenon may be applied to other events on Mars and points to a pattern of volcanism more common in its early history,” the research paper states.
The researchers used data from NASA’s Spirit rover, which is approximately 16 years old, and from the Perseverance rover in operation today. The location of both rovers on Mars contains the highest abundance of olivine to date identified on the planet. Similarities in the composition and morphology of large-scale separated olivine-rich rocks had not previously been investigated.
Now they seem to have formed in a similar way.
The false-color image on the left shows olivine-rich deposits in the Nili Fossae compared to the ground-welded igimbrite deposits (true colour). The fractures in the Earth example are cooling joints, which are very similar to those in the Mars example. Images by HiRISE / Google Earth
Olivine is a silicate mineral that comes from magma generated in the mantle of Mars, similar to how it formed on Earth.
“There are a lot of ideas about the origin of the olive-rich bedrock that covers large parts of an area called Nili Fossae, which includes Jezero crater. It’s a debate that’s been going on for nearly 20 years,” Arizona State University’s School of Earth and Space Exploration Steve Raff said in a statement.
Raff examined the mosaic of images from the Mars Spirit microscope imaging device and noticed rocks with an unusual texture. Then he compared it to pictures of rocks on Earth and came across some igneous rocks with a texture remarkably similar to that of the mosaic from Mars.
“That was an Eureka moment. I was seeing the same kind of textures in the Josef crater rocks as those in a very specific type of igneous rock found here on Earth.”
The images were an image of gyneimbrite forming as a result of lava ash flows, pumice and clumps from the largest known volcanic eruptions on Earth. These sediments then slowly cool, resulting in intricate networks of fractures known as cooling joints, which form as thick mounds of ash and pumice. Researchers have identified similar fracture patterns in olive-rich bedrock deposits on Mars.
Ignimbrites are found, on land, in Yellowstone National Park in the western United States dating back 2.1 million years. “No one had previously proposed imperites as an explanation for the olive-rich bedrock on Mars, and it is likely that this is the type of rock the Perseverance rover has been cruising and sampling over the past year,” Ruff said.
The new study indicates how violent changes in Earth have shaped the planet we see today, and the findings could pave the way for a deeper understanding of our neighboring planet.