Contemporary planetary science confirms that the lunar surface is continuouslybombarded by micrometeoroids with velocities approximately between 10 and 70km/s, leading to the process known as space weathering. This article drawsattention to an open question: if the universe is effectively lossless on largescales, and if interstellar material as well as remnants of supernovae may carrysubstantially higher velocities than ordinary local impactors, why does the lunarsurface not display a clear population of microcraters corresponding tosystematic bombardment by particles with velocities far exceeding the commonlyobserved range? I propose the hypothesis that this limitation of maximum impactvelocities may be consistent with the existence of a cosmic medium that, oververy long travel through galactic distances, gently modulates the energy anddynamics of high-velocity particles. In this interpretation, the medium does notact as simple viscous friction, but rather as a long-term filtering mechanism thatlimits the occurrence of extremely fast projectiles in the inner regions ofplanetary systems. The lunar surface may therefore provide an indirect empiricalindication of the existence of an environment that affects the propagation ofmatter on cosmic scales.
Aleš Hrůza (Wed,) studied this question.