No. 38: Mar-Apr 1985
Here follows an abstract of an article that appeared in Science:
"Nuclear tracks have been identified in interplanetary dust particles (IDP's) collected from the stratosphere. The presence of tracks unambiguously confirms the extraterrestrial nature of IDP's, and the high track densities (1010 to 1011 per square centimeter) suggest an exposure age of approximately 104 years within the inner solar system."
(Bradley, J.P., et al; "Discovery of Nuclear Tracks in Interplanetary Dust," Science, 226:1432, 1984.)
Comment. Where does this young dust come from? The Poynting-Robertson drag is supposed to sweep the inner solar system clear of dust fairly quickly. If comets supply a steady stream of dust, the particles should display a wide range of exposure ages.
|Apparent path of star SAO 186001 behind Neptune. The star's light was reduced at the black circle.|