The dissipation of the solar nebula constrained by impacts and core cooling in planetesimals

Rapid cooling of planetesimal cores has been inferred for several iron meteorite parent bodies on the basis of 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 Pd-107-Ag-107 decay system to date rapid core cooling by determining Pd-Ag ages for iron meteorites. We show that closure times for the iron meteorites equate to cooling in the time frame similar to 7.8-11.7 Myr after calcium-aluminium-rich inclusion formation, and that they indicate that an energetic inner Solar System persisted at this time. This probably 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 calcium-aluminium-rich inclusion formation could have reinforced this effect. This correlates well with the timing of impacts recorded by the Pd-Ag system for iron meteorites.

Automated summary

The rapid cooling of iron meteorite parent bodies has been dated using the Pd-107-Ag-107 decay system, showing that the closure times for these meteorites occurred around 7.8-11.7 million years after the formation of calcium-aluminium-rich inclusions. This suggests the persistence of an energetic inner Solar System during this time, possibly due to gas dissipation in the protoplanetary disk and the damping effect of gas drag ceasing. An early giant planet instability between 5 and 14 million years after calcium-aluminium-rich inclusion formation may have reinforced this effect, corresponding well with the timing of impacts recorded by the Pd-Ag system for iron meteorites.