Open AccessThe effect of backscattering on the drag force acting on sputtering bodies
Author(s) -
Coulson S. G.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10890.x
Subject(s) - meteoroid , physics , sputtering , drag , atmosphere (unit) , radius , scattering , astrobiology , mean free path , planet , mechanics , astrophysics , optics , meteorology , thin film , quantum mechanics , computer security , computer science
The recovery of discrete amounts of biotic material in the Earth's upper atmosphere raises the question of the detailed dynamics of these particles during atmospheric air breaking. Earlier work has discussed the possibility that these particles are slowed by the sputtering of surface molecules. The mechanics of sputtering are examined to take account of the scattering of molecules back on to the surface of a meteoroid. It is found that when the meteoroid radius is of the order of the mean free path of the surrounding atmosphere, backscattering can account for around a sixth of the drag, for meteoroid velocities <1 km s −1 . The effects of backscattering are not significant for the direct entry of micron‐sized particles into the atmosphere as these are decelerated at altitudes where the atmospheric mean free path is much greater than the particle's radius. Backscattering effects do appear to be significant, however, when considering the drag force acting on a micron‐sized particle moving through the atmosphere at a settling speed of the order of cm s −1 .