At some point this year, after NASA's rover Curiosity has landed on Mars, a laser will fire a beam of infrared light at a rock or soil sample. This will "ablate" or vaporize a microgram-sized piece of the target, generating a plume of ionized gas or plasma, which will be analyzed by spectrometers to identify the target's constituent elements. Future Mars rovers, however, will be able to do even more. Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), in collaboration with Applied Spectra, Inc., have developed an advanced version of this laser technology that can also analyze a target's constituent isotopes. This expanded capability will enable future rovers for the first time to precisely date the geological age of Martian samples.
Rick Russo, a scientist with Berkeley Lab's Environmental Energy Technologies Division and a pioneer in laser ablation spectroscopy, led the development of LAMIS for Laser Ablation Molecular Isotopic Spectrometry. As with the earlier Laser Induced Breakdown Spectroscopy (LIBS) technology being used on rover Curiosity, the basic premise is to use the energy of a high-powered laser beam focused to a tiny spot on the surface of a sample to create a plasma plume for analysis. Each species of atoms or ions within the plasma will emit light with signature spectral emission peaks. However, whereas LIBS only measures the optical emission spectra of atoms and ions, LAMIS measures the emission spectra of molecules and molecular ions. This enables LAMIS to identify the specific isotopes of a chemical element within the plasma plume.
"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 says. "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 nitr
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory