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Physical Chemistry

Ticket To Mars

Instrument builder retraces his path getting a spectrometer on the Mars rover Curiosity

by Celia Henry Arnaud
August 26, 2013 | A version of this story appeared in Volume 91, Issue 34

Red Rover: Inside the Story of Robotic Space Exploration, from Genesis to the Mars Rover Curiosity, by Roger Wiens, Basic Books, 2013, 256 pages, $25.99 hardcover (ISBN: 978-0-465-05598-2)
Title and author, with photo of the rover Curiosity on desert landscape.
Red Rover: Inside the Story of Robotic Space Exploration, from Genesis to the Mars Rover Curiosity, by Roger Wiens, Basic Books, 2013, 256 pages, $25.99 hardcover (ISBN: 978-0-465-05598-2)

When I was in graduate school, I had a bad habit of complaining that things couldn’t possibly get worse. “Don’t challenge worse; things can always get worse,” a lab mate cautioned. My friend could have been talking to Roger Wiens, a scientist at Los Alamos National Laboratory, as he recites the litany of the many challenges he and his team faced in building and operating Chemical Camera (ChemCam), one of the instruments on Curiosity, the Mars rover most recently deployed by the National Aeronautics & Space Administration.

As readers of Wiens’s book, “Red Rover: Inside the Story of Robotic Space Exploration, from Genesis to the Mars Rover Curiosity,” we have the benefit of hindsight. We know that Curiosity nailed its landing on the Red Planet, successfully deployed its various instruments, and continues to gather data about Mars. But such success was far from guaranteed.

Wiens tries to give us the sensation of being there when success was not ensured. But he diminishes the tension right from the start. In his prologue, he describes the successful launch of Curiosity in November 2011. Although he doesn’t start with the landing on Mars—he saves that for the climax of the book—he gives any readers not already clued in enough to know that this story has a happy ending. He then backtracks and unspools the tale of how the rover got to that point.

Before focusing on Curiosity, however, Wiens starts with his first NASA mission. Genesis was a 2004 mission to bring solar-wind samples back to Earth. Wiens helped design and build the sample collectors, an array of high-purity silicon wafers. On its return to Earth, the capsule containing the samples crashed in the Utah desert. Luckily, the researchers were able to recover many of the samples anyway.

Wiens then turns to ChemCam and the Curiosity rover. In real life, the Genesis and ChemCam timelines overlapped, but for clarity, Wiens keeps the two separate.

ChemCam, a laser-induced breakdown spectroscopy (LIBS) system, had troubles of its own. After receiving initial funding, the team got caught in a standoff between NASA headquarters and the Jet Propulsion Laboratory, which refused to test a prototype instrument on its rover because LIBS had not yet been approved for a mission. Then the instrument was picked for testing on an identical rover at NASA’s Ames Research Center, and the testing was to be done in the Nevada desert. But a wildfire in New Mexico forced the evacuation of Los Alamos and prevented the team from getting there. That first test was canceled. A laser accident on the day of the proposal deadline for the final instrument selection shut down work at Los Alamos. Luckily, Wiens’s team had already submitted the proposal. In December 2004, Wiens learned that the review panel picked ChemCam for the rover.

Credit: NASA/JPL-Caltech/LANL
Wiens is shown testing ChemCam, which uses a pulsed laser beam to vaporize a pinhead-sized target.
This image from testing of the instrument shows ChemCam Principal Investigator Roger Wiens, of Los Alamos National Laboratory, observing the light from a plasma ball induced by the laser hitting a sample rock from a distance of about 3 meters (10 feet). The laser beam itself is invisible. The plasma is hazardous to the naked eye at close range.
Credit: NASA/JPL-Caltech/LANL
Wiens is shown testing ChemCam, which uses a pulsed laser beam to vaporize a pinhead-sized target.

After ChemCam was picked to be one of the instruments on the as-yet-unnamed rover, Wiens’s team continued to run into problems. First they struggled to find detectors that performed well under the anticipated conditions. Then they had trouble finding optical fibers for transferring light to the spectrometer. At one point, ChemCam was canceled for projected cost overruns, only to be quickly reinstated.

Even after the instrument was finished, both it and the rover had to go through a grueling series of “shake and bake” tests to show that they could survive the mechanical vibrations and temperature fluctuations they would experience. And NASA ended up delaying the launch for two years. (To be fair, the delay was that long because once they missed their launch window, that’s how long it was before Earth and Mars were again properly aligned.)

After his rundown of the many problems overcome along the way, Wiens finally brings us back to Cape Canaveral for Curiosity’s November 2011 launch, which went off without a hitch. But Wiens—remembering his experience with Genesis—continued to be plagued by dreams of all the things that could still go wrong. Fortunately, none of those nightmares came true, and so far the Curiosity mission has been a smashing success.

I enjoyed the book, especially learning about NASA politics, but I do have some quibbles.

For example, after readers finish “Red Rover,” they probably won’t know any more about LIBS than they did when they picked up the book. Wiens writes about his own first encounter with the technique: “As I watched, Dave [Cremers, then a spectroscopist at Los Alamos] connected the battery and pressed a button. ‘Zap!’ An invisible beam shot across the room to the rock and produced a brief flash. Dave turned on a screen for a spectrometer, a small instrument that can distinguish colors with great sensitivity, and displayed the color spectrum of the flash. He explained that the spectrum consisted of unique colors from each of the elements present in the rock. Zapping a rock of another composition produced a different mix of colors.” And that’s pretty much the extent of the explanation of LIBS.

I also found an example where Wiens seems to have things wrong. In his description of “Sample Analysis at Mars” (SAM), a suite of three instruments that make up most of the science payload on Curiosity, Wiens says SAM contains a gas chromatograph, a quadrupole mass spectrometer, and a laser mass spectrometer. I wasn’t sure what he meant by a laser mass spectrometer, so I did some research. It turns out that SAM contains a “tunable laser spectrometer,” basically a simple absorption spectrometer used to measure concentrations and isotope ratios of methane, carbon dioxide, and water vapor. There may be other examples; that’s just the one that jumped out at me.

Of course, Curiosity’s journey is not yet complete. Even more quickly than Curiosity answers existing questions about our nearest neighbor, new questions arise, waiting for their chance to be asked. Much remains to be discovered.

Celia Henry Arnaud is a senior editor at C&EN.


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