The fate of formamide in a fragmenting protoplanetary disc

TL;DR

This study combines hydrodynamic simulations and chemical modeling to explore the evolution of formamide, a pre-biotic molecule, in a fragmenting protoplanetary disc, revealing its phase distribution and potential inheritance by forming planetary cores.

Contribution

It provides the first detailed simulation of formamide behavior in a fragmenting disc, linking chemical evolution with dynamical processes during early planetary formation.

Findings

Formamide remains mostly frozen on grains in the cold disc regions.

It appears in the gas phase in high-temperature fragments.

Solid-phase formamide abundance matches comet observations.

Abstract

Recent high-sensitivity observations carried out with ALMA have revealed the presence of complex organic molecules (COMs) such as methyl cyanide (CH$_{\rm 3}$CN) and methanol (CH$_{\rm 3}$OH) in relatively evolved protoplanetary discs. The behaviour and abundance of COMs in earlier phases of disc evolution remains unclear. Here we combine a smoothed particle hydrodynamics simulation of a fragmenting, gravitationally unstable disc with a gas-grain chemical code. We use this to investigate the evolution of formamide (NH$_{\rm 2}$CHO), a pre-biotic species, in both the disc and in the fragments that form within it. Our results show that formamide remains frozen onto grains in the majority of the disc where the temperatures are $<$100 K, with a predicted solid-phase abundance that matches those observed in comets. Formamide is present in the gas-phase in three fragments as a result of the high temperatures ($\geq$200\,K), but remains in the solid-phase in one colder ($\leq$150 K) fragment. The timescale over which this occurs is comparable to the dust sedimentation timescales, suggesting that any rocky core which is formed would inherit their formamide content directly from the protosolar nebula.