Plot showing mass resolution of C, N and O isotopes on Voyager

Principal Results from Voyager Isotope Studies

• The decay of electron-capture isotopes such as 50Ni, 51Cr, and 49V can be used to date the acceleration of cosmic rays. These suggest that CR are accelerated long after a supernova explosion - probably from ambient IS material and that the acceleration occurs in a short time scale with little acceleration during the subsequent 10M year propagation time through the galaxy to us.

• Isotopic composition of cosmic rays is almost exactly solar to within a few percent. This means that the mass composition of the material used to make cosmic rays and the sun has changed very little in the 4.5B years since the sun was formed.

• The differences in isotopic composition eg. 22Ne may suggest that cosmic rays are enriched by Wolf-Rayet star ejecta.