Martian Volcanoes Once Chose Violence
Structures in rocks imaged by the Spirit rover reveal similarities to ignimbrite rocks here on Earth, which means some very ancient eruptions were more explosive than expected.
We now turn to volcanos on Mars. And specifically, we’re going to talk about a point in time when some of those volcanoes may have chosen violence.
First, some background information. Almost twenty years ago, there were two little rovers that landed on Mars — Spirit and Opportunity. They were both planned out as ninety-day missions, but as I’m sure a lot of you recall, they lasted far longer than that. And about sixteen years ago, Spirit explored Gusev crater and found bedrock that was rich in olivine. Cool, olivine. If you’re like me, you probably are asking, “What’s olivine?” I’ve actually asked that question.
Olivine is a green mineral that comes from magma in the mantle, both on Mars and here on Earth. It’s not really unexpected, but it is definitely a clear signal of some kind of volcanic activity occurring that brought those rocks to the surface.
Fast forward to the past year on Mars and a newer, much bigger rover named Perseverance. You know, the rover the helicopter is running around with. Anyway, there are also olivine-rich rocks over in the Nili Fossae region where Jezero crater is being explored by Percy. And both of these locations, despite not being close to one another, have the highest abundance of this mineral so far found on Mars. Which, of course, intrigued scientists as to how craters ended up with similar rocks.
Enter a team of scientists trying to link the two locations by their volcanic history. Their work, led by Steve Ruff and published in the journal Icarus, involved testing the leading hypothesis that the olivine was deposited as part of gently falling ash. They analyzed images from Spirit’s Microscopic Imager and discovered rocks with an interesting texture. By comparing those images to a catalog of Earth rocks, they found similarities, but those similarities mean the eruptions were far more violent than expected.