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Scientists made a laser that can detect explosives from half a mile away

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The system could map out whole areas of land according to their fertilizer and drug content

Hokr et al. / PNAS

Imagine a plane that can fly over large areas of land while identifying hidden stockpiles of drugs or explosives — that's the idea driving the development of remote laser sensing technologies. But until recently that goal had really only been achieved over short distances. Now, a new study, published today in Proceedings of the National Academy of Sciences, brings us that much closer to chemical-detecting planes, as researchers were able to use a single shot of laser light to detect individual chemicals located 1 kilometer (0.6 miles) away.

"This opens up the door to an entirely new method for remote sensing," said Vladislav Yakovlev, a biomedical engineer at Texas A&M University and a co-author of the study, in an email to The Verge. Previous studies have described similar laser sensing technologies, he said, but "No one has been able to obtain such long distances, and especially not on a single-shot basis."

"No one has been able to obtain such long distances."

The technique makes use of "Raman scattering," a physical phenomenon that involves light passing through a material, causing it to vibrate at a level that’s specific to the molecules contained in the material. The ensuing scattering of light causes a color change in a small percentage of the laser pulses that hit the target. "The color change of the light is unique to the specific chemical," Yakovlev explained, "so we then detect the color of the light and that allows us to identify the specific chemical." This is allowed the scientists to differentiate similar-looking powders like ammonium nitrate and sodium nitrate — both of which can be used to make bombs — from 400 meters (0.2 miles) away.

Right now, the whole system can be assembled for around $30,000, but the researchers hope to make it more "real-world friendly" over the course of the next few years. To do this, however, they will have to identify which conditions are optimal for irradiation in addition to making sure that the device can identify mixtures of chemicals as accurately as it can identify individual components. And it's reasonably safe, the researchers say, as the only real potential for harm is the effect that the laser might have on human eyes — something that operators can avoid by wearing eye protection.

Regulators could detect fertilizers from the comfort of a plane's cockpit

"Remote detection of explosives is a really big thing," Yakolvev said. "Our hope is that this technique will allow for the detection of hazardous chemicals from a safe distance in real time." The military applications for a device like this are pretty obvious, but there are many non-military applications as well. Law enforcement might be able to use the system to detect drugs, for instance.

"Considering that it takes just one laser shot to quantify the presence of specific compounds on a ground," Yakovlev said, "one can imagine mapping the large area quickly identifying locating and quantifying the presence of such compounds" from the comfort of a plane's cockpit. It could even be used in future space missions to Mars, he said. "You can imagine putting such remote sensing system on a satellite, and probing each spot on the ground" for signs of life on other planets.