Jupiter’s Migration and the Hydration of the Early Inner Solar System

Abstract:

Determining the timing, flux and source of water accretion in the early solar system is important for understanding planet formation and habitability, and for constraining models of the movements of the giant planets during terrestrial planet formation. Angrite meteorites are ideal for studying early solar system processes; they sample one of the oldest planetesimals. Angrites are depleted in volatile elements compared to Earth. Plotting condensation temperature vs normalized mantle abundance, Na and K are depleted in the angrite parent body (APB) compared to Earth, yet the APB has an elevated Rb/Na (see Fig). To elucidate this inconsistency, we examined the volatile elements H, C, F, and Cl because these elements have 50% condensation temperatures ranging from 40 to 948 K.

Here we report measurements of volatile and major element concentrations in olivines from D’Orbigny and Sahara 99555. Our olivine major, minor and volatile data closely matches a forward fractional crystallization model, which means (1) post crystallization diffusion of H is minor and (2) we were able to calculate the H, C, F, and Cl abundances of the APB melt. We are able to reproduce the volatile metal depletion trend of the APB and its relative volatile element enrichment from our H, C, F, and Cl data in combination with published data by adding ~ 0.3 % carbonaceous chondrites to a volatile-poor reservoir.

The antiquity of angrites in combination with their volatile contents demonstrates that inner solar system bodies accreted water and volatile elements very early. The kinks in the volatile element depletion diagram (see fig) suggest that both volatile-poor and volatile-rich components were accreted to the APB. One mechanism for large scale mixing in the inner solar system leading to early accretion of volatiles is a giant planet-migration event. The “Grand Tack” is a dynamic early solar system model that predicts that carbonaceous chondrite material entered the initially dry inner solar system at some point during planet formation. It provides one possible mechanism for the transport of volatile-rich material into the inner solar system. Our results constrain the timing of volatile addition and, therefore, provide a time constraint for the Grand Tack – or for alternative models that explain the addition of volatiles to the inner solar system.