Mariek Schmidt ’99, a geology major at Colby, is a postdoctoral fellow in the department of mineral sciences at the Smithsonian National Museum of Natural History. After writing her dissertation on North Sister in the Three Sisters volcanic field in Oregon, she joined the mission working with the Mars rover Spirit. She spoke with Colby staff writer Laura Meader about rocks, water, and life on Mars.
How did you become a volcanologist?
Volcanology is just a sub-discipline of geology. One of the first upper-level geology classes you take at Colby is called mineralogy. Each mineral tells a story about how it formed. You look at a rock, it has a particular mineral in it, you could say something about how that rock formed. And you can start to put together a story of that rock or the plate that the rock was formed in.
Volcanology is following that to the next level—it’s exciting and it’s active. I got into volcanology because I was interested in the chemistry of rocks and the minerals in them.
You’re working with the Spirit rover. Aren’t there two rovers on Mars?
The Mars rover mission began at two different sites in 2004. They chose these sites thinking they were going to find sedimentary rocks. The Opportunity rover did find sedimentary rock. But the Spirit rover was at Gusev Crater and they thought they were going to find lakeshore deposits and instead they found basaltic lava. Fairly early on in the mission people were kind of disappointed with what Spirit had found, because there wasn’t evidence for water. That was the whole goal of the mission, to find evidence of water at that particular crater.
You were brought on to the mission after they found the volcanic rock?
Basically they realized that there are very few people on the mission that could interpret volcanic rock. The other people on the mission who work with chemistry and mineralogy of rock are people who either work on meteorites—so they work on igneous rock but they're rocks that have no geologic context—or they think about things from orbit.
How does a volcano on Mars differ from one on Earth?
The largest volcano in the Solar System is found on Mars. It’s called Olympus Mons. It absolutely enormous. It’s equivalent in size to the state of Arizona. The reason why that volcano—and others on Mars—is so big is because on Mars there’s no plate tectonics.
A volcano like Hawaii is a hot spot volcano. What happens at Hawaii is there’s a stream of hot magma that’s focused in one place. And we have plates that move over the top of that hot spot on the Earth. Because that plate is moving over the top of it, you have a line of volcanoes that are downstream of it. On Mars there’s no plate tectonics. So everything that forms in that one hot spot is built up in one place.
Why are there no plate tectonics on Mars?
It’s actually because of the size—it’s a smaller planet. Mars is two-thirds the size of the Earth. So basically it’s cooled to a point where there’s nothing that’s driving flow within the mantle anymore.
What was it like studying Mars after working with Earth rocks?
It’s been an interesting transition coming from a terrestrial background where I’m used to being able to handle rocks and walk around the field. Now I’m in a field where it’s a mission, so there’s a lot of people involved. There’s engineers, there’s planetary geologists, there’s meteorists, there’s people who develop the instruments. … So I went from a situation where I was a single researcher and then became part of this bigger thing. But I bring to it a different perspective because I had the terrestrial background.
Do you have to vie for attention?
Yeah, we do actually. Let’s say the rover is driving someplace and I see a rock that I think is really interesting. In order for that rover to actually go over and examine that rock, I have to come up with a workable plan for that to occur. And not only do I have to come up with a workable plan, I have to come up with a hypothesis for why we would study it.
For example, the Spirit rover has been in a place called Home Plate for almost three years. Home Plate is a platform of bedrock. It’s only 80 meters across. And one side of the structure has one kind of mineralogy and the other side of the structure has another kind. So there’s what we call a mineralogical gradient across it. I suggested that we do a series of observations using the chemical equipment to analyze the structure along a traverse to track how that mineralogy changes.
There’s such a mystique about Mars. What's it like working with Martian rocks?
It’s definitely different from working on Earth. On Earth we have so much data—we have existing theories we can work with and, basically, most things we learn on Earth we fit it into our preexisting understanding of the planet. Whereas on Mars we only know information about a handful of sites. We have the orbital view, which is really great right now, but we’ve only landed successfully in a handful of places.
When you’re studying the raw data, is there much difference between data from Earth and Mars?
It’s different because the instruments we use are very different. For example on Earth, when I look at terrestrial rocks, a lot of times I’ll look at a thin section under a microscope, where you see the mineralogy very, very well and you can see the texture very, very well. But on Mars we can’t do that sort of thing. We’re basically left with what’s visible as the outer surface of the rock.
Do you have a favorite image of Mars or a favorite area?
I’m attached to Home Plate—I’ve done most of my work on it. My favorite image was one that we took—it was actually taken in black and white—but it was taken at a low sun angle, so it was taken pretty late in the day. Usually when the sun goes down we shut off the rover in order to conserve power, so it’s rare to get these kinds of pictures. But what you can see in it are these beautiful shadows across the plate. It’s just a stunning image.
Beyond the search for water, are you looking for something specific?
Now we’ve found water at both sites. At Opportunity rover we found water and it looks like it was a sedimentary system. At the Spirit site we found evidence for water as well and it turns out to be these hydrothermal deposits, which are basically rocks that have been altered by water and volcanic gases. Now we’re interested in what the nature of that water is or the nature of those volcanic acids and whether or not they could sustain an environment that could possibly have life. We’re getting more of an understanding of environment as opposed to just “is there water?”
Do you think there was once life on Mars?
We haven’t found it. I think it’s possible.
In what form?
I don’t think there’s going to be dinosaurs walking around. I’m imagining something more in the lines of scum. Microbes, things that might digest rocks or that might use hydrothermal fluids to get energy. Things like that.
If you had the chance, would you travel to Mars?
(Long pause.) It depends on whether or not I could come back. There’s always the possibility that you wouldn’t return, and I don’t think that my husband would be that happy about that.