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LASER L I T T L E I C E N C E G S BIG A universally useful tool pioneered and perfected at Los Alamos is exploring other planets and improving life on this one. Mars’s Mount Sharp, the source of new geological LIBS data that suggest Mars may have once been flush with both liquid water and atmospheric oxygen. CREDIT: NASA/JPL/MSSS some tools, like a crosshead screwdriver, are only good at the task for which they were invented. Others, however, like a flathead screwdriver, are often useful for tasks beyond their original one. Over 30 years ago, scientists at LosAlamos developed a tool for watershed preservation that detects and measures naturally occurring toxic metals in soil. That tool is now being used in various scientific endeavors, from exploring Mars’s chemical makeup to protecting precious pipelines. Laser-induced breakdown spectroscopy (LIBS) is a technique that reveals the presence and concentration of elements in a sample. A small but powerful laser is used to vaporize a miniscule amount of material from the surface of the sample, creating a tiny plasma that contains energetically excited atoms. As the plasma cools, the atoms emit light at wavelengths characteristic of their elements and a spectrometer measures the light emissions, which are then used to calculate the concentration of each type of atom in the sample. LIBS is handy because it’s virtually nondestructive, portable, adaptable, rapid, remote (can measure a sample from a distance), and affordable—which is why it can be used in so many environments, including other worlds. The latest news from Mars came via ChemCam, a Los Alamos LIBS analyzer aboard the rover Curiosity. Deposits of manganese oxide and strong silica enrichment were discovered, suggesting that liquid water may have been present much later, and that there may have been more oxygen in the planet’s past, than was previously thought. “Manganese deposits only formed on Earth after the rise of photosynthesis, when the atmosphere was flooded with free oxygen produced by photosynthetic microbes,” explains Los Alamos planetary scientist Nina Lanza. The manganese deposits on Mars suggest that Mars too had significant amounts of oxygen in its atmosphere at some point, although the source of that oxygen is still unclear. One hypothesis is microbes. Another is that the oxygen came from water molecules being split by ionizing radiation, resulting in the lighter hydrogen atoms escaping Mars’s atmosphere and the heavier oxygen atoms staying behind. 14 1663 December 2016 Laser-induced breakdown spectroscopy, or LIBS, is a technique to reveal what elements are present in a sample. A powerful laser is used in quick, successive pulses to ablate nanograms of material from the sample’s surface, creating a micro-plasma in which energetically excited atoms dissociate into ions and electrons. As the excited atoms and ions lose their excess energy, they emit characteristic wavelengths of light, and a spectrometer is used to resolve the wavelengths and measure the intensity of those emissions to determine which elements are present in the sample and in what relative proportions. The discovery of rocks strongly enriched with silica led to two more discoveries. First, the detection of tridymite, a silicate mineral that is rare on Earth, was the first-ever evidence of Martian silicic volcanic activity, which is a specific type of explosive volcanism. “The second discovery,” Lanza’s colleague astrogeologist Jens Frydenvang explains, “came from where, within Mars’s bedrock, we found high-silica. It was along the fractures, which suggests that liquid water was present much later than previously thought—extending the time period in which Mars could have supported microbial life.” As successful as ChemCam has been, Los Alamos scientists are eager for data from the next rover, scheduled to launch in 2020. Its updated Los Alamos instrument dovetails LIBS with Raman spectroscopy, a technique that identifies specific molecules, complementing the elemental analysis of LIBS. Back here on Earth, LIBS is proving to be quite useful for national security in several arenas. LIBS can be used by International Atomic Energy Agency inspectors to rapidly detect the presence of nuclear material in a variety of samples, with little-to-no sample preparation. Because LIBS can distinguish between different isotopes of the same element,