The rapid formation of macromolecules in irradiated ice of protoplanetary disk dust traps

TL;DR

This study proposes that organic macromolecules in protoplanetary disks can form rapidly in dust traps through irradiation, linking planetesimal formation with the origin of organic matter essential for life.

Contribution

It introduces a mechanism for fast formation of organic macromolecules in irradiated dust traps within protoplanetary disks, connecting planetesimal formation to organic chemistry.

Findings

Up to 4% of disk ice can be converted into macromolecules.

Radiation doses enable transformation within several decades.

Organic matter formation is linked to dust trap environments.

Abstract

Organic macromolecular matter is the dominant carrier of volatile elements such as carbon, nitrogen, and noble gases in chondrites -- the rocky building blocks from which Earth formed. How this macromolecular substance formed in space is unclear. We show that its formation could be associated with the presence of dust traps, which are prominent mechanisms for forming planetesimals in planet-forming disks. We demonstrate the existence of heavily irradiated zones in dust traps, where small frozen molecules that coat large quantities of microscopic dust grains could be rapidly converted into macromolecular matter by receiving radiation doses of up to several 10s of eV molecule$^{-1}$ year$^{-1}$. This allows for the transformation of simple molecules into complex macromolecular matter within several decades. Up to roughly 4$\%$ of the total disk ice reservoir can be processed this way and subsequently incorporated into the protoplanetary disk midplane where planetesimals form. This finding shows that planetesimal formation and the production of organic macromolecular matter, which provides the essential elemental building blocks for life, might be linked.