Countdown to Mars: Caltech goes to the Red Planet
On Sunday, August 5, the Mars Science Laboratory (MSL) rover, known as Curiosity, will make its dramatic descent onto Mars's surface. Once it lands, the rover will check its instruments to make sure everything's functioning properly—and then it will get right to work.
In fact, on just the second day of its Martian excursion, Curiosity is scheduled to turn on some of its key scientific instruments, taking pictures and making measurements of its immediate environment. About a week later, the rover will spin its six wheels and start exploring. Curiosity will ramp up its science mission over the following weeks, deploying its suite of instruments to scoop, drill, zap, examine, and analyze. And through it all, a couple of Caltech researchers will be among the 300 scientists working here on Earth, taking the information Curiosity sends home and trying to figure out what it all means.
Back in February, Caltech's Ken Farley and Bethany Ehlmann were named as participating scientists on the mission; each will be directing their own Martian science projects. Ehlmann, an assistant professor of planetary science and a JPL research scientist, has been analyzing rocks and minerals on Earth to help MSL's science team choose which Martian rocks to study in detail. Farley, the W. M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences, will measure the presence of noble gases in Martian rocks to determine their ages. Here are some excerpts from Kimm Fesenmaier's story about how these two scientists intend to make their mark on Mars.
Examining the capabilities of one of Curiosity's science instruments, Sample Analysis at Mars (SAM), which was designed to look for organic matter, Farley realized that it might be possible to detect the isotope helium-3 with SAM's spectrometer. Since helium-3 is produced by the bombardment of surface materials by incoming cosmic rays, measurements of the isotope can be used to determine how long rocks or other geologic features have been exposed on the surface of a planet. This could help scientists date features on Mars such as impact craters, but it could also come in handy in terms of target selection.
Imagine, for example, that the science team locates an impact site on Mars that seems to have been created within the last few million years. The rocks around that site would be ideal targets for closer study because any organic matter they contain would have been protected from cosmic rays until they were thrown out onto the surface. "The trouble is, it's easy to say that an impact happened a million years ago, but how would you ever really know?" Farley says. "The technique that I have is a way to say, 'Yes, this is, in fact, a very young surface.'"
Farley says his involvement with MSL is a major departure from his previous work, as he has not been heavily involved in the study of the geology of Mars. "Most of what I do is technique development," he says. "So it's interesting for me to see potential application of one of those techniques in another very different setting."
In contrast, space missions are Ehlmann's bread and butter. She got her first taste of rover operations while an undergraduate student working on the Mars Exploration Rovers mission. Then as a graduate student, she was a collaborator on the Mars Reconnaissance Orbiter mission and used data from multiple orbiters to locate hydrated minerals on the surface of the red planet.
For MSL, Ehlmann proposed to help improve the team's ability to select rocks from a distance for more extensive study. Curiosity is equipped with a laser and a telescope known collectively as ChemCam, mounted on its mast. From a distance of about seven meters, the laser can zap a rock to create a plasma, which can be analyzed with the ChemCam spectrometer to get a sense of the chemical elements present. The science team needs to be able to use those results and their knowledge of mineralogy to quickly decide whether to spend more time and energy on a particular target or to keep Curiosity moving.
To give them a leg up, Ehlmann is analyzing rocks from places such as Iceland as well as synthetic mixtures of minerals in the lab that are similar to the materials observed from Mars orbit at the Gale Crater landing site. The rocks can be well characterized in Earth laboratories to understand their mineralogy, the elements they are made of, and how they would appear from orbit. She is studying how they have been changed by different types of interaction with water. She plans to take the samples to Los Alamos National Laboratory, which partnered with the French national space agency to build the ChemCam, in order to test her samples with a ChemCam-like instrument.
"It's very helpful to have this beforehand understanding of what you might see or what kinds of analyses you need to run," Ehlmann says. "If you understand the processes enough that you develop quick-look algorithms for detecting different styles of alteration, it will help in the tactical timescale when you only have a few hours to come up with a plan for the rover for the next day."
