The Dissipation of the Solar Nebula Constrained by Impacts and Core Cooling in Planetesimals

TL;DR

This study uses Pd-Ag dating of iron meteorites to constrain the timing of rapid core cooling and impact events in the early Solar System, revealing a period of energetic activity between 7.8 and 11.7 million years after CAI formation.

Contribution

It provides new age constraints on core cooling and impact timing in planetesimals using Pd-Ag dating, linking these events to Solar System evolution.

Findings

Core cooling occurred between 7.8 and 11.7 Myr after CAI.

Impacts and core cooling are temporally correlated.

Gas dissipation and giant planet instability influenced impact history.

Abstract

Rapid cooling of planetesimal cores has been inferred for several iron meteorite parent bodies based on metallographic cooling rates, and linked to the loss of their insulating mantles during impacts. However, the timing of these disruptive events is poorly constrained. Here, we used the short-lived 107Pd / 107Ag decay system to date rapid core cooling by determining Pd-Ag ages for iron meteorites. We show closure times for the iron meteorites equate to cooling in the timeframe ~7.8 to 11.7 Myr after CAI, and indicate that an energetic inner Solar System persisted at this time. This likely results from the dissipation of gas in the protoplanetary disk, after which the damping effect of gas drag ceases. An early giant planet instability between 5 and 14 Myr after CAI could have reinforced this effect. This correlates well with the timing of impacts recorded by the Pd Ag system for iron meteorites.