Composition of distant stars can be explored by observing absorption spectra. Stars produce nearly blackbody radiation that passes through the cloud of vaporized material surrounding the star. Characteristic absorption lines are discernible with a spectrometer, and atomic composition is investigated by comparing spectral observations with known material profiles. Most objects in the solar system—asteroids, comets, planets, moons—are too cold to be interrogated in this manner. Material clouds around cold objects consist primarily of volatiles, so bulk composition cannot be probed. Additionally, low volatile density does not produce discernible absorption lines in the faint signal generated by cold objects. We propose a system for probing the molecular composition of cold solar system targets from a distant vantage. The concept utilizes a directed energy beam to melt and vaporize a spot on a distant target, such as from a spacecraft orbiting the object. With sufficient flux (~10 MW/m2) on a rocky asteroid, the spot temperature rises rapidly to ~2500 K, and evaporation of all materials on the surface occurs. The melted spot creates a high-temperature blackbody source, and ejected material creates a molecular plume in front of the spot. Bulk composition is investigated by using a spectrometer to view the heated spot through the ejected material. Spatial composition maps could be created by scanning the surface. Applying the beam to a single spot continuously produces a borehole, and shallow sub-surface composition profiling is possible. Initial simulations of absorption profiles with laser heating show great promise for molecular composition analysis.


Statistics and Probability

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