Curiosity's Mission to Mars

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By John Severance

One can see why Roger Wiens monitors the website, www.ustream.tv/nasaijpl, on a continuous basis. The site provides a camera into the clean room at NASA's Jet Propulsion Laboratory in Pasadena, Calif., where the next Mars rover is being built.
Wiens, a geochemist with the U.S. Department of Energy’s Los Alamos National Laboratory, has more than a vested interest. Wiens serves as ChemCam’s principal investigator and he makes occasional trips to California to check on the rover, which is named Curiosity.
So what is ChemCam exactly?
It is a rock-zapping laser instrument that can hit rocks with a laser powerful enough to excite a pinhead-size spot into a glowing, ionized gas. ChemCam then observes the flash through a telescope and analyzes the spectrum of light to identify the chemical elements in the target.
According to a press release from the Jet Propulsion Laboratory, that information about rocks or patches of soil up to about 7 meters (23 feet) away will help the rover team survey the surroundings and choose which targets to drill into, or scoop up, for additional analysis by other instruments on Curiosity. With the 10 science instruments on the rover, the team will assess whether any environments in the landing area have been favorable for microbial life and for preserving evidence about whether life existed.
“When we zap the rocks, the telescope collects the light and then we map it against the patterns of standards we have already analyzed,” Wiens said. “Once in a while, we hit an unusual mineral and we have to do some research to figure out what it is.”
Also according to the release, the pinhead-size spot hit by ChemCam’s laser gets as much power focused on it as a million light bulbs, for five one-billionths of a second. Light from the resulting flash comes back to ChemCam through the instrument’s telescope, mounted beside the laser high on the rover’s camera mast. The telescope directs the light down an optical fiber to three spectrometers inside the rover. The spectrometers record intensity at 6,144 different wavelengths of ultraviolet, visible and infrared light. Different chemical elements in the target emit light at different wavelengths.
 If the rock has a coating of dust or a weathering rind, multiple shots from the laser can remove those layers to provide a clear shot to the rock’s interior composition. “We can see what the progression of composition looks like as we get a little bit deeper with each shot,” Wiens said.
A sizeable team of engineers in Los Alamos and in Toulouse, France has worked since 2004 to jointly develop, build, and test the ChemCam instrument.
 In late 2011, NASA will launch the unmanned Curiosity rover from Cape Canaveral in Florida and the other parts of the flight system, delivering the rover to the surface of Mars in August 2012.
The rover team was hoping for a launch in 2009, but a number of parts of Curiosity were not ready yet.
“It was pretty clear we were not going to make it then,” Wiens said. “The biggest problem was the motors that drive the six wheels, steer the rover, and move the antenna, arm, and gimbals.” Wiens said, as of now, everything is on schedule for a late November launch.
It will take eight months to get to Mars and at that particular point, the planets will be about 35 million miles apart.
So where is the Rover going to land when it gets to Mars? That is up for discussion, but there are four options that are being considered.
The sites are:
• Eberswalde Crater, which contains a clay-bearing delta formed when an ancient river deposited sediment, possibly into a lake.
• Gale Crater, which contains a 5-kilometer sequence of layers that vary from clay-rich materials near the bottom to sulfates at higher elevation.
• Holden Crater, which has alluvial fans, flood deposits, possible lake beds and clay-rich sediments.
• Mawrth Vallis, which exposes layers within Mars’ surface with differing mineralogy, including at least two kinds of clays.
Ultimately, Wiens said that decision will be made by the head of NASA, but any of the four sites would be fascinating. “We just wish we had four rovers,” Wiens said.
When the rover lands, Wiens said it will have the capability of moving at least 15 miles in its journey. The rover is designed to last over one Mars year which translates into at least two Earth years.
“It has to navigate its way around on its own each day,” Wiens said, “as communication with the rover only occurs once a day. Unlike the previous rovers, which relied on solar power, this rover is run by a radio isotope thermal generator (RTG).”
During the rover mission, Wiens and the French and U.S. teams will analyze the samples from ChemCam nearly every day. In the meantime, the ChemCam team will count the days until liftoff, making last-minute tests of the instrument whenever possible.
“It’s a process that continues to unfold,” Wiens said.