Ablation on the horizon: LAMIS lands

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  • Published: Mar 15, 2012
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Ablation on the horizon: LAMIS lands

Long-distance LAMIS

US researchers are developing the next generation of laser ablation technology, which might one day be used in a future planetary lander to carry out isotopic analysis of a planet's surface, for instance, and so allow precise "geological" ages of samples to be determined. The technique, LAMIS, is not yet as sensitive or precise as mass spectrometry but has the advantage of requiring no chemical dissolution, sample preparation, vacuum chambers or laboratory infrastructure, a boon for a planetary lander.

NASA's Curiosity rover will soon be blasting the Martian surface with infrared laser light and analysing the plasma plume that results. However advanced the ensuing spectroscopic data, there is the potential for a future generation of space explorer to do so much more thanks to work being carried out by researchers at the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab). Rick Russo and colleagues, Alexander Bol'shakov, Xianglei Mao, at Berkeley Lab are working with Applied Spectra, Inc to develop an advanced version of laser ablation technology that will be able to analyse the isotopic fingerprint of rock and other samples.

LAMIS, Laser Ablation Molecular Isotopic Spectrometry, is not dissimilar to the Laser Induced Breakdown Spectroscopy (LIBS) technology that the NASA Curiosity rover carries. However, LAMIS measures more than the optical emission spectra of atoms and ions observed by LIBS. LAMIS can also determine the emission spectra of molecules and molecular ions and can identify the specific isotopes of a chemical element within the plasma plume.

Molecular beats atomic

"Relative to atomic emission, molecular spectra can exhibit significantly larger isotopic shifts due to the contributions of the vibrational and rotational motion in the molecule," Russo explains. "The trick is to be patient and wait for the hot atoms and ions in the plasma to collide and merge with the ambient environment to form an oxide, or a nitride or fluoride, and then collect the molecular light emissions," he adds.

Russo's group has been using LAMIS to study isotopes of strontium, an alkaline earth metal commonly found in geological and natural materials. Although strontium's major isotopes are stable (strontium-90 being a radioactively notable exception), the percentage of strontium-87 will naturally increase over time as a result of the decay of radioactive rubidium. By comparing the ratio of strontium-87 to strontium-86 it is possible to date geological and oceanographic samples. The technique can even be applied to archaeology. However, current techniques for strontium isotope ratio determination using mass spectrometry is time-consuming, labour-intensive and requires laboratory sample preparation, all of which are somewhat precluded if the samples are to be analysed by a robotic rover on a distant planet.

"The next step is to improve the sensitivity and precision of LAMIS," Russo says. "Our immediate target is parts-per-million, which should be relatively easy for us to reach, but ultimately we want to get to parts-per-billion sensitivity, which will be a challenge. However, 50 years ago, the parts-per-billion sensitivity of today's mass spectrometry technologies would have been thought impossible," he adds. He and his colleagues envisage applications for LAMIS in industry, medical diagnostics and nuclear security.

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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