Contemporary interstellar meteoroids in the solar system - in situ measurements and clues on composition

Abstract

Meteoroids originating from the local interstellar medium, traverse the solar system. This has been proven by in situ measurements by interplanetary spacecraft as well as highly sensitive radar measurements. Early attempts to detect interstellar meteoroids using the instruments on board the Pioneer 8 and 9 spacecraft failed. More sensitive detectors on board the joint ESA/NASA mission Ulysses as well as on board the NASA spacecraft Galileo, however, unambiguously detected meteoroids of interstellar origin. This discovery has started efforts to compare the results from the in situ measurements with highly sophisticated models of interstellar dust properties derived from astronomical absorption and extinction measurements. It was found that, at least locally, is more mass locked up in meteoroids than expected from the astronomical measurements. So far the in situ measurements only allow to derive composition information indirectly via the meteoroid's dynamics.