Now that NASA's "seven-minutes of terror" have passed safely, the Mars Curiosity rover's exploratory mission is off and running. Over the next two years—probably more, if it's anything like the Opportunity or Spirit rovers—the Jeep-sized rover will explore its new home using a variety of tools. One of the Curiosity's most important objectives will be to help researchers understand how Mars transformed over the past 3.5 billion years of geologic time into a drier, less hospitable planet.

For that, the six-wheeled mobile laboratory will rely heavily on a ChemCam laser characterization instrument and several other devices it is set to carry on its projected 19-kilometer journey. ChemCam—developed at Los Alamos National Laboratory (LANL) and the French space institute (IRAP)—is designed to rapidly analyze rock and soil compositions outside the rover, identifying samples that could be studied further by additional instruments inside the rover. The LANL-built CheMin, for example, will use X-ray diffraction to determine the composition of mineral samples collected and dropped into the rover via a funnel.

ChemCam's analysis begins when the rover's mast-mounted laser fires a pulse at an area the size of a pinhead, vaporizing part of its target from several meters away. The laser can fire three pulses per second. The first few will remove dust that would otherwise obscure the target surface, enabling scientists to better observe the underlying sample. Curiosity then uses a telescope to view the glowing flash of plasma left behind and record the colors of light within that flash. A spectrometer analyzes the colors, allowing scientists to determine the elemental composition of the vaporized material.

On August 17 or 18, researchers expect ChemCam will be the first device to perform active remote sensing on the Martian surface, according to LANL, which designed the unit to look for lighter elements indicative of life such as hydrogen, carbon, nitrogen and oxygen. The system is designed to make as many as 14,000 observations throughout the mission.

The 900-kilogram rover touched down safely on the surface of Mars early Monday morning, Eastern Daylight Time. Part of the autonomously navigated landing sequence included slowing from 21,000 kilometers per hour at the top of Mars' atmosphere to a dead stop on the surface, all in the space of seven minutes.

Curiosity's home during the mission is Gale Crater, a basin more than 150 kilometers in diameter close to the planet's equator with stacks of sedimentary layers that are taller than those found in Arizona's Grand Canyon. As a whole, the $2.5-billion mission should help scientists determine what Mars was like during an earlier, wetter era, and whether the planet could have once been hospitable to extraterrestrial life over a sustained period of time.

Artistic rendering courtesy of Jean-Luc Lacour, via Los Alamos National Laboratory (LANL)