Migration of D-type asteroids from the outer Solar System inferred from carbonate in meteorites

TL;DR

This study uses carbonate isotope analysis in meteorites to infer that some D-type asteroids originated in the cold outer Solar System and migrated inward due to planetary orbital instability.

Contribution

It demonstrates that high 13C/12C ratios in meteorite carbonates indicate formation of D-type asteroids in the outer Solar System, revealing their migration history.

Findings

High 13C/12C ratios in Tagish Lake carbonates exclude organic sources.

D-type asteroids likely formed in cold outer Solar System regions.

Migration of D-type asteroids into the inner Solar System is linked to giant planet instability.

Abstract

Recent dynamical models of Solar System evolution and isotope studies of rock-forming elements in meteorites have suggested that volatile-rich asteroids formed in the outer Solar System beyond Jupiter's orbit, despite being currently located in the main asteroid belt. The ambient temperature under which asteroids formed is a crucial diagnostic to pinpoint the original location of asteroids and is potentially determined by the abundance of volatiles they contain. In particular, abundances and 13C/12C ratios of carbonates in meteorites record the abundances of carbon-bearing volatile species in their parent asteroids. However, the sources of carbon for these carbonates remain poorly understood. Here we show that the Tagish Lake meteorite contains abundant carbonates with consistently high 13C/12C ratios. The high abundance of 13C-rich carbonates in Tagish Lake excludes organic matter as their main carbon source. Therefore, the Tagish Lake parent body, presumably a D-type asteroid, must have accreted a large amount of 13C-rich CO2 ice. The estimated 13C/12C and CO2/H2O ratios of ice in Tagish Lake are similar to those of cometary ice. Thus, we infer that at least some D-type asteroids formed in the cold outer Solar System and were subsequently transported into the inner Solar System owing to an orbital instability of the giant planets.