Rocky Planet Formation: Quick and Neat

TL;DR

This paper suggests that rocky planet formation may be faster and cleaner than previously thought, explaining the low observed warm dust around stars despite high terrestrial planet occurrence rates.

Contribution

It proposes that rapid and neat rocky planet formation accounts for the low warm debris disk incidence, challenging traditional assumptions.

Findings

High terrestrial planet occurrence contrasts with low warm dust incidence.

Gas drag in residual gas can efficiently remove warm dust.

Rocky planet formation may be quicker and cleaner than previously believed.

Abstract

We reconsider the commonly held assumption that warm debris disks are tracers of terrestrial planet formation. The high occurrence rate inferred for Earth-mass planets around mature solar-type stars based on exoplanet surveys (roughly 20%) stands in stark contrast to the low incidence rate (less than 2-3%) of warm dusty debris around solar-type stars during the expected epoch of terrestrial planet assembly (roughly 10 Myr). If Earth-mass planets at AU distances are a common outcome of the planet formation process, this discrepancy suggests that rocky planet formation occurs more quickly and/or is much neater than traditionally believed, leaving behind little in the way of a dust signature. Alternatively, the incidence rate of terrestrial planets has been overestimated or some previously unrecognized physical mechanism removes warm dust efficiently from the terrestrial planet region. A promising removal mechanism is gas drag in a residual gaseous disk with a surface density of roughly or somewhat more than 0.001% of the minimum mass solar nebula.