We present laboratory measurement of vapor produced by simulated micrometeoroid bombardment, with direct relevance to the study of surface-bounded exospheres around the Moon, Mercury and other solar system bodies. Exciting new in-situ observations from MESSENGER at Mercury, and the anticipation of results from LADEE at the Moon, have highlighted the uncertainty surrounding the role of micrometeoroid impacts in sustaining tenuous planetary exospheres. In a recent series of experiments at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS), the quantity of neutral molecules generated by impacts of simulated micrometeorids in the 0.1-0.5 micron size range was measured using a fast ion gauge over a speed range of 1-12 km/s. We find that the quantity of neutrals released per unit projecile mass, N=m, is consistent with a power law in the projectile speed v. At the highest speeds tested, the number of neutrals liberated is equivalent to 1% of the atoms in the projectile; at speeds encountered at the Moon (20 km/s), near-complete vaporization is projected.
Published on May 9, 2013