The iodine-plutonium-xenon age of the Moon-Earth system revisited

TL;DR

This study revisits the timing of Earth's formation and the Moon-forming event using iodine-plutonium-xenon isotopic data, accounting for atmospheric xenon loss over geological time to refine age estimates.

Contribution

It introduces a new model that corrects for xenon loss, providing revised age constraints for Earth's atmosphere and the Moon-forming impact.

Findings

Minimum Xe formation interval is 40 Ma after solar system start.

Revised closure ages for Earth's atmosphere align with mantle Xe ages.

Suggests the Moon-forming impact occurred around 40 Ma after solar system formation.

Abstract

From iodine-plutonium-xenon isotope systematics, we re-evaluate time constraints on the early evolution of the Earth-atmosphere system and, by inference, on the Moon-forming event. Two extinct radioactivites (129I, T1/2 = 15.6 Ma, and 244Pu, T1/2 = 80 Ma) have produced radiogenic 129Xe and fissiogenic 131-136Xe, respectively, within the Earth, which related isotope fingerprints are seen in the compositions of mantle and atmospheric Xe. Recent studies of Archean rocks suggest that xenon atoms have been lost from the Earth's atmosphere and isotopically fractionated during long periods of geological time, until at least the end of the Archean eon. Here we build a model that takes into account these results. Correction for Xe loss permits to compute new closure ages for the Earth's atmosphere that are in agreement with those computed for mantle Xe. The minimum Xe formation interval for the Earth- atmosphere is 40 (-10+20) Ma after start of solar system formation, which may also date the Moon-forming impact.