UV photolysis, organic molecules in young disks, and the origin of meteoritic amino acids

TL;DR

This paper suggests that ultraviolet photolysis in young protoplanetary disks irradiated by nearby stars could have produced complex organic molecules, including amino acid precursors, within the early Solar System.

Contribution

It introduces a new model where UV irradiation in the Sun's protoplanetary disk creates complex organics, offering an alternative to previous aqueous or interstellar formation theories.

Findings

UV irradiation can produce amino acid precursors rapidly.

The model suggests sufficient organic production within 1 million years.

External UV flux could be much higher than solar UV alone.

Abstract

The origin of complex organic molecules such as amino acids and their precursors found in meteorites and comets is unknown. Previous studies have accounted for the complex organic inventory of the Solar System by aqueous chemistry on warm meteoritic parent bodies, or by accretion of organics formed in the interstellar medium. This paper proposes a third possibility: that complex organics were created in situ by ultraviolet light from nearby O/B stars irradiating ices already in the Sun's protoplanetary disk. If the Sun was born in a dense cluster near UV-bright stars, the flux hitting the disk from external stars could be many orders of magnitude higher than that from the Sun alone. Such photolysis of ices in the laboratory can rapidly produce amino acid precursors and other complex organic molecules. I present a simple model coupling grain growth and UV exposure in a young circumstellar disk. It is shown that the production may be sufficient to create the Solar System's entire complex organic inventory within 10^6 years. Subsequent aqueous alteration on meteoritic parent bodies is not ruled out.