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Why does Mars Curiosity rover have a laser raygun?

NASA's Mars rover, Curiosity, is armed with a laser to zap rocks, not Martians. The laser can vaporize rocks at a distance of 23 feet.

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This artist's conception depicts the rover Curiosity, of NASA's Mars Science Laboratory mission, as it uses its Chemistry and Camera (ChemCam) laser.

REUTERS/NASA/JPL-Caltech

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Yes, NASA's Mars rover has a laser gun.

But there are no plans for Curiosity to zap Martians.

This cool little laser – and it is tiny – is designed to vaporize a pin-head sized area of Martian rock. The laser heats up the rock, and turns it into a glowing ionized gas. It's part of an instrument on the rover Curiosity known as the "ChemCam." The ChemCam observes the flash of vaporized rock and analyzes the spectrum of light to identify the chemical elements in the rock. The laser has a range of about 23 feet.

Here's how NASA describes the process:

"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 ChemCam analysis proves interesting, the Curiosity rover can move in and drill or scoop up an actual sample of the rock. The pulse laser can also be used to "dust off" an interesting rock formation with a series of short bursts. 

NASA officials note that earlier Mars rover missions have been unable to identify some of the lighter elements, such as carbon, oxygen, hydrogen, lithium and boron. They note, for example, that a Mars mission in 2005 looked at an outcrop called "Comanche," and it took years of analyzing indirect evidence before the team could confidently infer the presence of carbon in the rock. ChemCam can identify carbon with one shot.

The idea for putting a laser on a Mars rover is traced by NASA back to 1997. At the time, Roger Wiens was a geochemist with the US Department of Energy's Los Alamos National Laboratory, and was working on an idea for using lasers to investigate the moon. Wiens visited a chemistry laboratory building where a colleague, Dave Cremers, had been experimenting with a different laser technique. Cremers set up a cigar-size laser powered by a little 9-volt radio battery and pointed at a rock across the room.

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