The formation of Jupiter by hybrid pebble–planetesimal accretion

Abstract

The standard model for giant planet formation is based on the accretion of solids by a growing planetary embryo, followed by rapid gas accretion once the planet exceeds a socalled critical mass 1 . The dominant size of the accreted solids (cm-size particles named pebbles or km to hundred km-size bodies named planetesimals) is, however, unknown 1,2 . Recently, high-precision measurements of isotopes in meteorites provided evidence for the existence of two reservoirs in the early Solar System 3 . These reservoirs remained separated from ~1 until ~ 3 Myr after the beginning of the Solar System's formation. This separation is interpreted as resulting from Jupiter growing and becoming a barrier for material transport. In this framework, Jupiter reached ~20 Earth masses (M ⊕ ) within ~1 Myr and slowly grew to ~50 M ⊕ in the subsequent 2 Myr before reaching its present-day mass 3 . The evidence that Jupiter slowed down its growth after reaching 20 M ⊕ for at least 2 Myr is puzzling because a planet of this mass is expected to trigger fast runaway gas accretion 4,5 . Here, we use theoretical models to describe the conditions allowing for such a slow accretion and show that Jupiter grew in three distinct phases. First, rapid pebble accretion brought the major part of Jupiter's core mass. Second, slow planetesimal accretion provided the energy required to hinder runaway gas accretion during 2 Myr. Third, runaway gas accretion proceeded. Both pebbles and planetesimals therefore have an important role in Jupiter's formation.

A water budget dichotomy of rocky protoplanets from 26Al-heating

“…If, however, the main growth of rocky planets may proceed from the accumulation of small particles, such as pebbles, then the deviation between 26 Al-rich and 26 Al-poor systems may become less clear, and the composition of the accreting pebbles needs to be taken into account. Therefore, in future work, models of water delivery and planet growth need to synchronize the timing of earliest planetesimal formation (Drażkowska & Dullemond 2018), the mutual influence of collisions (Lichtenberg et al 2018) and 26 Al dehydration, the potential growth by pebble accretion (Johansen et al 2015;Schiller et al 2018;Alibert et al 2018), and the partitioning of volatile species between the interior and atmosphere of growing protoplanets (Ikoma et al 2018) in order to further constrain the perspectives for rocky exoplanet evolution (Kite & Ford 2018).…”

Accretion of the Earth—Missing Components?

“…This is often called the NC reservoir as compared to the carbonaceous chondrite (CC) reservoir, defined by CC. The two reservoirs are also referred to as solar system dichotomy and may have been separated by the early formation of Jupiter (Olsen et al 2016;Kruijer et al 2017;Alibert et al 2018) or a ringed structure in the protoplanetary disc (Brasser and Mojzsis 2020). The CI chondrites fall on the extension of the trend of the NC material together with the Earth as the closest body to the NC reservoir (Fig.…”

The origin of s-process isotope heterogeneity in the solar protoplanetary disk

“…It is possible that the composition of infalling material also changed with time and/or thermal processing 30,31,55 . Complete homogenisation between the inner and outer Solar System is blocked by the formation of Jupiter's core 55,56 , which leads to two compositionally slightly different reservoirs.…”