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Why Mars rover will be blasting its heat ray as it searches for life

The Mars rover Curiosity, which is due on the Red Planet next week, is outfitted with an infrared laser and telescope package called ChemCam that will vaporize bits of rock to study its chemical makeup.

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The beam plants 1-million-watt pulses on the spot for about five-billionths of a second each, heating the rock or dust it encounters to more than 3,500 degrees Fahrenheit, vaporizing the material.

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From a hypothetical Martian's standpoint, the beam's encounter with rock looks like the spark from a butane barbecue lighter. But the spectrum from that tiny bit of light carries an enormous amount of information about the types of atoms present in the material vaporized and their relative abundance.

Indeed, the device is the only one aboard the rover that can identify atoms across the entire periodic table of elements, giving researchers more opportunity to test the makeup of rock types they didn't anticipate finding.

By comparing the results ChemCam delivers from Mars with the spectra of up to 2,000 so-called calibration samples on Earth, researchers will be able to identify the rocks and minerals ChemCam zaps.

And if the rock of interest is covered with dust? No worries. A series of pulses from ChemCam's laser becomes the high-tech whisk broom that exposes the rock surface scientists really want to analyze.

Yet even before ChemCam reaches the Martian surface, researchers are trying to tailor the approach to provide dates for rocks on other planets, much as geochemists date rocks on Earth.

The idea is to detect a sample's spectrum in even finer detail than ChemCam does, so that it picks up not just the signatures of atoms, but their variants, known as isotopes.

By comparing the relative abundance of specific isotopes, researchers will have a more precise tool for gauging the age of rock formations they encounter with future rovers. Currently, they get merely a qualitative estimate of age by counting craters or mapping the relative positions of different geologic features.

On Earth with state-of-the-art technology, dating rocks with a high degree of precision is still a difficult process, says Ralph Milliken, a planetary scientist at Brown University in Providence, R.I., and a member of the Mars Science Laboratory science team. It's highly unlikely for rover-based approaches to match the precision of measurements made on labs on Earth, he says.

Still, "even if you could get the absolute age of something plus or minus 500 million years, that would be huge for Mars," he says.

Gale Crater, Curiosity's landing site, "is a good example. There is a debate as to the age of the material inside that crater" – a debate that yields an estimate that ranges over a billion years.

The latter half of that estimate bumps up against the end of the planet's earliest, and presumably wettest, period. With rock ages uncertain to within a billion years, did the rocks of interest in the crater really come from a wetter period, or from later dryer period?

It's a debate that bears directly on whether a young Mars – at least at this location – hosted potential habitats for life. It's a debate that the technology behind ChemCam eventually could help answer.

IN PICTURES: Exploring Mars


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