THE CONSTANCY OF THE GALACTIC COSMIC RAYS: THE CONTRIBUTION OF COSMOGENIC NOBLE GASES AND RADIONUCLIDES IN IRON METEORITES

The temporal constancy of galactic cosmic rays (GCRs) over the last few billion years is an important and long-standing question in meteorite research. Over the years, meteorites have been intensely studied to answer this question [1]. While travelling in space, meteoroids are exposed to GCRs and the nuclear interactions produce (among others) stable (noble gases) and radioactive cosmogenic nuclides. Being interested in the long-term variation of the GCRs, we study iron meteorites because they typically have cosmic ray exposure (CRE) ages in the range of a few million years (Ma) and for some even up to 2Ga [2]. It has been demonstrated previously that periodic GCR flux variations can induce peaks in CRE age histograms, which is due to the fact that during periods of high fluency the apparent time seems to run faster and vice-versa. Therefore, setting up a consistent exposure age histogram and then searching for periodic peaks would make it possible to study GCR flux variations.