The partitioning of the inner and outer Solar System by a structured protoplanetary disk

Abstract

Mass-independent isotopic anomalies define two cosmochemically distinct regions: the carbonaceous and non-carbonaceous meteorites1, implying that the non-carbonaceous (terrestrial) and carbonaceous (Jovian) reservoirs were kept separate during and after planet formation. The formation of Jupiter is widely invoked to explain this compositional dichotomy by acting as an effective barrier between the two reservoirs2. Jupiter’s solid kernel possibly grew to 20 Earth masses ( $${M}_{\oplus }$$ ) in 1 Myr from the accretion of submetre-sized objects (‘pebbles’), followed by slower accretion via planetesimals. Subsequent gas envelope contraction led to Jupiter’s formation as a gas giant3. Here, we use dynamical simulations to show that the growth of Jupiter from pebble accretion is not fast enough to be responsible for the inferred separation of the terrestrial and Jovian reservoirs. We propose instead that the dichotomy was caused by a pressure maximum in the disk near Jupiter’s location, which created a ringed structure such as those detected by ALMA4. One or multiple such—potentially mobile—long-lived pressure maxima almost completely prevented pebbles from the Jovian region reaching the terrestrial zone, maintaining a compositional partition between the two regions. We thus suggest that our young Solar System’s protoplanetary disk developed at least one and probably multiple rings, which potentially triggered the formation of the giant planets. The early Solar System might have been similar to the ringed protoplanetary disks observed by ALMA. One of the gaps, at Jupiter’s position, could be the cause of the observed dichotomy between carbonaceous and non-carbonaceous material.