Origins of fossil charged-particle tracks in meteorites

Abstract

In this paper we consider the possible origins of naturally occurring (fossil) charged-particle tracks in meteorites. The fact that only particles with a large rate of ionization loss give revealable tracks in common silicate minerals restricts the sources of meteoritic tracks to the following possibilities: (a) slowed-down heavy cosmic-ray primaries, (b) spontaneous fission of U238 and extinct Pu244, (c) induced fission of heavy elements by cosmic rays, (d) spallation recoils, (e) meson jets, and (f) magnetic monopoles. The last two potential sources are probably not important. The other sources are shown to produce characteristic track features that allow the dominant source to be uniquely identified in individual meteorites—provided the appropriate calibration experiments are performed. Two important applications of fossil meteoritic tracks are the determination of the abundance of extremely heavy cosmic rays and the measurement of the cool-down time of bodies in the early solar system.