Directed energy stand-off molecular composition analysis

A scheme is described for probing the molecular composition of cold solar system targets such as asteroids, comets, planets and moons from a distant vantage. A laser beam is directed at a spot on a distant target, such as from a spacecraft orbiting the object. With sufficient flux, the spot temperature rises rapidly, and evaporation of materials on the target surface occurs; ejected material creates a molecular plume of target material. The melted spot serves as a high-temperature blackbody source, and bulk composition is investigated by analyzing absorption that occurs when blackbody radiation from the heated spot passes through the molecular cloud. The method is described as Remote Laser Evaporative Molecular Absorption (R-LEMA) Spectroscopy. Spatial composition maps could be created by scanning the directed energy beam across the surface. Applying the laser beam to a single spot continuously produces a borehole (or trench, for rotating objects), and shallow sub-surface composition profiling is also possible. Simulations of absorption profiles with laser heating show promise for molecular composition analysis. This study presents results of simulations showing the molecular absorption profiles for selected molecular species.