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 Sample Analysis at Mars (SAM) instrument suite is consists of three instruments and three supporting subsystems that will investigate the chemistry of the Martian surface and atmosphere. The three instruments in the suite are a quadrupole mass spectrometer, a gas chromatograph and a tunable laser spectrometer.

Roughly the size of a microwave oven, SAM will analyze gases evolved from solid samples delivered by the robotic arm and atmospheric samples that are inhaled directly from the martian atmosphere.

SAM will detect both organic and inorganic compounds, and it will measure stable isotopes of key chemical elements as well, including carbon, oxygen, hydrogen and sulfur.

Pan Conrad, deputy principal investigator of the SAM team, will be studying the materials on the surface of the red planet and trying to reconstruct its history.

What kind of science do you generally do? What is your area of expertise?
I'm an astrobiologist, specializing in the assessment of habitability, mainly in contemporary environments on the planetary surface.

I chose the term "assessment" deliberately because it is not something simply measured unless one happens across something living, but rather a measurement of the whole array of factors that could be critical to an environment's habitability potential.

We have a unique opportunity in Gale Crater, because we have such a diverse payload that we can measure a wide array of variables that could affect the habitability potential of the environment there.

We can then think about how to extrapolate the environmental measurements back in time so we can look in the rock record at Gale to discover what features consistent with habitable environments might look like once preserved in the rock records.

When sedimentary rocks are made, they record the environment at the time they are deposited, so it's important to remember that record can be altered over time.

So the preservation potential of various environments affects the accuracy with which we can interpret the rock record. To top it off, we have to infer habitability for an environment that isn't Earth and the potential of habitability for life that may not be like life on Earth. We have to keep a very open mind. It's a really tough problem.

There are some caveats. We have to recognize that we're being Earth-centric. We also have to be careful about making inferences about past environments, when what we're really looking at is environments of deposition from sediment that was already weathered from yet a former environment.

For example, in a fluvial depositional environment, once the little grains of sediment have been put in place by that river, we're looking at a structure during the time the sediment was deposited and recording the information in the rock record.

But before that sediment got recorded and placed where we can see it, each grain of that sand was weathered away from another rock, in some other environment, in some other time before it was deposited.

So we're always looking at two or more time periods when we're looking at sedimentary rock-the time periods represented by the grains before they became weathered away from a rock and placed into the sedimentary record, and then the time period during which they were deposited and frozen or recorded.

How does that tie in with MSL?
To evaluate habitability, one thing to do is look at the present environment. We can measure a lot of things, chemically and physically. We can look at the constituents of the atmosphere, which is what SAM does, just "inhaling" through our atmospheric inlets.

MSL can also look at the chemistry and the mineralogy, the materials where the rover is working. We can look at things that are components of the rock and the sediment in different layers of rock, and that's how we look back in time at former Martian environments.

There are lots of questions we can address with images: When we look at a rock, do we see similarities amongst the kinds of grains with respect to sizes and shapes? Are there sedimentary structures such as layers, ripples, etc? What clues to past can we observe?

Then, as we look at the chemical composition of all the material-and that means both the gases and the solids on Mars, we can begin to develop models about what the raw materials are and how they have been processed over time.

We get information about physics in the present by looking at things like solar radiation? What is the temperature? How does the temperature vary over the day? How about atmospheric pressure?

How does that vary over the season? How does the incoming radiation environment vary over the days of our mission? The RAD instrument constantly measures our radiation environment.

As we look at things like wind speed and wind direction, we get a sense of the physical dynamics of the environment. The structures, as well as the shapes and sizes of minerals, tell you something about the dynamics of the past environment of deposition.

It's complicated, and we have to try to understand not only what the martian materials are made of but also what they are doing as a function of the environmental forces over time.

How could your work help us to answer questions about astrobiology?
Well, as you know, trying to understand the habitability potential of another planet is straight out of the Astrobiology Roadmap. Trying to understand the habitability potential of at least one other planet begins to address the larger question of, what is the potential distribution of life throughout the solar system?

But in a very meaningful way, as we begin to look at the processes that have weathered the surface of a planet that was created at the same time as our own, then we begin to look at the breadth and diversity of both the material and the processes.

As we do that, we begin to get a feel for what might be too dynamic, what might be insufficient raw material, and what might be indicative of the probability for those requirements that at least the life we know about would place on an environment.

At a fundamental astrobiological science level, MSL is trying to assess the past and present potential of the Martian environment to support life.