Cosmogenic nuclide enhancement via deposition from long-period comets as a test of the Younger Dryas impact hypothesis

TL;DR

This study investigates whether long-period comets could have deposited enough cosmogenic nuclides like 14C, 10Be, and 26Al to explain anomalies observed during the Younger Dryas period, providing a potential test for impact hypotheses.

Contribution

It quantifies the nuclide content on long-period comets and proposes the 26Al/10Be ratio in ice cores as a definitive test for the Younger Dryas impact hypothesis.

Findings

Large comets could deposit sufficient isotopes to cause observed anomalies.

The 26Al/10Be ratio is significantly higher in extraterrestrial material than in Earth's atmosphere.

Measuring this ratio in ice cores can test the impact hypothesis.

Abstract

We explore the idea that detectable excursions in 26Al may arise from direct deposition by any bolide, and excursions in 14C and 10Be abundances in the atmosphere may result from long-period comet impacts. This is very different from the usual processes of production by cosmic rays within Earths atmosphere. Long-period comets experience greatly increased cosmic ray flux beyond the protection of the suns magnetic field. We report the computed amount of 14C, 10Be, and 26Al present on long-period comets as a function of comet mass. We find that the amount of nuclide mass on large long-period comets entering the Earths atmosphere may be sufficient for creating anomalies in the records of 14C and 10Be from past impacts. In particular, the estimated mass of the proposed Younger Dryas comet is consistent with its having deposited sufficient isotopes to account for recorded 14C and 10Be increases at that time. The 26Al/10Be ratio is much larger in extraterrestrial objects than in the atmosphere, and so, we note that measuring this ratio in ice cores is a suitable definitive test for the Younger Dryas impact hypothesis, even if the hypothetical bolide is not a long-period comet and/or did not contribute to the 14C and 10Be increases.