Curious About Life: Interview with Dawn Sumner
The Mars Science Laboratory Curiosity rover has 10 science instruments, and each will be used in the coming weeks and months to help characterize the environment of Mars and determine if the planet ever had the potential for life.
The Mastcam system is the eyes of MSL, helping scientists to decide which direction to send the rover and what samples to study in depth. Dawn Sumner is one of the scientists using the Mastcam to move Curiosity across the Martian surface.
What kind of science is it that you generally do?
I would consider myself an astrobiologist. My main research, besides this mission, is trying to understand the early evolution of microbial communities. I do that by characterizing fossil communities from the rock record. I worked quite a bit on Archaean ones, but I’ve worked on rocks of all ages. I also study modern analogs – cyanobacterial communities living in ice-covered lakes in Antarctica. I’m trying to understand the morphology and community structure of those, how the biology shapes the community in a way that can get preserved morphologically in the rocks.
So the microbial communities in the stromatolites sometimes have an ambiguous origin. Shapes in some cases can also be attributed to abiotic processes. I tend to work on structures composed of organic matter encased in the rocks. We know that they’re organic, and they have a morphology that’s complicated enough that we don’t have any models for how they would form abiotically. We take the fossils that look the most microbial and try to see if we can understand the microbial processes that create those structures.
For example, my students make serial sections of some of these stromatolites, and then they visualize them in three dimensions. We look at the shapes of the peaks, the slopes of the lamina and things like that.
I also work with people like Roger Summons to look at the organics associated with the fossils.
What do you do specifically for MSL?
I got involved with MSL because a lot of my work in the Earth rock record requires interpreting depositional environments. What was the environment like? What was the water depth? In early 2000, I worked with the Mars Exploration Program Analysis Group (MEPAG)—a group that’s sponsored by NASA for advice on Mars research—to describe how to search for life on Mars.
MEPAG has a document called the Goals Document that lays out the science priorities for Mars research. It’s in four parts, one of which is to determine if life ever arose on Mars. Andrew Steele and I took on rewriting the goals for the search for life on Mars, at about the same time that the MSL mission was being defined. We ended up with a document that said we should look for habitable environments and try to understand the carbon cycle. Those were picked up by the MSL mission as part of the mission goals.
Then I ended up part of the proposal for the scientific cameras through Malin Space Science Systems. When that proposal was funded, I became part of the MSL mission. As the mission evolved, I became very involved in landing site selection because of my experience characterizing ancient environments on Earth. I co-chaired the MSL project landing site selection working group, and I did a lot of work characterizing two of the landing sites.
Since then, I’ve been co-chairing a group to make a geologic map of Gale Crater and our landing area. On the mission, I’m a member of the camera team and I’m also one of the long-term planners, helping to make sure that the daily decisions on the mission fit with the mission goals, and that we’re doing the science that we should be doing to address the mission goals.
You said that you’re a member of the camera team. What does that entail?
The camera team first designed and built the cameras, and I didn’t play a very big role in that because that’s not my expertise. But now we’re operating the cameras. Various people write the commands to take the images, and people like me advise other team members on good images to take, how to best use the cameras, and things like that. Then I work a lot on interpreting the images that we do take.
Obviously it’s not like a conventional camera where you’ll be standing on Mars and be like, "I’m going to try and take this picture." How do you determine what images and how to make that happen?
It’s a really interesting challenge, because usually, on Earth, you look around and you go, "I want a picture of that." But the cameras are the eyes of the rover and you don’t see anything unless you ask Curiosity to take a picture. There are also engineering cameras. When we first landed, we took a 360 degree panorama of where we were. We know from the orbiting instruments where we landed, so we can combine the images from the orbiter and Curiosity So then we say, "Okay, these areas look interesting," and as we drive, we think, "Maybe we should take a new image in this direction to see what we can see from our new location."
Good example: we drove east in an area called Glenelg. We were on a plateau with a slope going down to Glenelg. We couldn’t see over the lip of that plateau, so we used the topography information we have from orbit and the images we have from the rover, and we predicted where we would be able to see interesting things. Then we ask the rover to take another panorama. Also, there are a group of people that are really interested in taking images off to the side of the rover every so often, maybe every drive or every two times we drive, so we can see what the surface we’re on is like.
There are lots of things that you can take pictures of, but we don’t have an infinite amount of time or memory to do that. We have to make scientific arguments about why the image we want will be interesting and useful. Often they are, and sometimes they are not. Sometimes we take a picture of something and then it’s like, "Well, that’s not very informative."
How did you feel when the rover landed and you got that first look at Mars?
It was really exciting. I tend to be an optimist, and I talked to the engineers enough to have a lot of confidence in them, so I wasn’t so worried about landing safely, but it was really exciting that we did land. For me, one of the coolest things of all was when we figured out where we landed, because we had this mapping project beforehand, using the orbiter data, and we’d landed in an area that I mapped. We had this pool to see who would choose the closest point to where we landed, and I actually picked one a little bit east of Glenelg because that’s where I thought it was most interesting. I wasn’t the closest person, but we landed in a place where we could go where I thought it was most interesting.
And then getting the first images back of Mount Sharp—well, I broke down and cried when I saw Mount Sharp because I had spent so much time looking at it from orbit. To actually see it from the ground was just amazing.
How can your work with MSL help to answer astrobiology questions?
The most important question is whether or not life is elsewhere in the Universe. Mars is the closest place we can look on the ground. Everything we know about Mars to date suggests that it had at least some water at the surface at some time in the early history, and there ought to be carbon. When you have water and volcanic minerals, there’s at least a potential for an energy source. It has sunlight, even though it’s less than Earth, so we have the minimum components that would be necessary for life to be present.
We don’t know how life emerged, what the origin of life was. Mars is similar enough to Earth—with significant differences—that it’s conceivable that life could have originated on Mars. If it didn’t, we could learn about what happens on an abiotic planet that provides insight to see how life might have originated on Earth, where we don’t have any of that record on Earth.
On Earth, our oldest rocks are four billion years old, and they don’t preserve very much information at all. On Mars, most of the rocks are older than three billion years. So you have this opportunity to study a really early planet and those processes that are key either to prebiotic chemistry or an early biosphere. We don’t know which is present on Mars, but either way, that’s the important question to ask. Now, we have to do these investigations with a rover, and we’ve only been to a few places on Mars, so we’re taking baby steps and hopefully we’ll find organic compounds using the SAM instruments. If we do, the characteristics of those will tell us a lot about how they’re preserved and what the carbon cycle might be like on Mars.
The Gale landing site is a great one, in that we already have evidence of water there, and we have evidence of hydrous minerals from orbit. It’s a place where, if life existed, there’s a chance we could find some clues to it, and if life didn’t exist, we can still learn about the ancient environment on Mars, how the rock formed and possibly something about the carbon cycle.
Okay, what would you be the most excited to discover or to see on Mars?
The most important thing for me would be to find organic carbon. That’s something that people have been searching for for decades, since the Viking mission, and it ought to be there, if only from carbonaceous chondrites, a type of meteorite. So I think that, to me, is the most important next step in trying to understand and determine whether life ever arose on Mars.