Interaction of infalling solid bodies with primordial atmospheres of disk-embedded planets

TL;DR

This study investigates how infalling solid bodies interact with primordial atmospheres of embedded planets, revealing significant atmospheric heating and cooling effects that challenge classical assumptions about energy transfer.

Contribution

It introduces a detailed model of energy transfer during planetesimal infall, showing that a substantial portion of gravitational energy heats the atmosphere, contradicting previous models.

Findings

Large planetesimals dissipate energy into the atmosphere.

Infall can cause local atmospheric cooling for planets with cores > 2 Earth masses.

Classical models underestimate atmospheric energy exchange.

Abstract

Planets that form early enough to be embedded in the circumstellar gas disk accumulate thick atmospheres of nebular gas. Models of these atmospheres need to specify the surface luminosity (i.e. energy loss rate) of the planet. This luminosity is usually associated with a continuous inflow of solid bodies, where the gravitational energy released from these bodies is the source of energy. However, if these bodies release energy in the atmosphere instead of at the surface, this assumption might not be justified. Our aim is to explore the interactions of infalling planetesimals with primordial atmospheres at an embedded phase of evolution. We investigate effects of atmospheric interaction on the planetesimals (mass loss) and the atmosphere (heating/cooling). We used atmospheric parameters from a snapshot of time-dependent evolution simulations for embedded atmospheres and simulated purely radial, infall events of siliceous planetesimals in a 1D, explicit code. We implemented energy transfer between friction, radiation transfer by the atmosphere and the body and thermal ablation; this gives us the possibility to examine the effects on the planetesimals and the atmosphere. We find that a significant amount of gravitational energy is indeed dissipated into the atmosphere, especially for larger planetary cores, which consequently cannot contribute to the atmospheric planetary luminosity. Furthermore, we examine that planetesimal infall events for cores, $M_\mathrm{C} > 2$M$_{\oplus}$, which actually result in a local cooling of the atmosphere; this is totally in contradiction with the classical model.