First Detection of the Simplest Organic Acid in a Protoplanetary Disk

TL;DR

This paper reports the first detection of formic acid in a protoplanetary disk, indicating active organic chemistry that could influence planetary system formation.

Contribution

It presents the first observational evidence of formic acid in a protoplanetary disk, expanding understanding of organic molecule synthesis in early planetary environments.

Findings

Detected formic acid (HCOOH) in the TW Hydrae disk.

Found HCOOH column density comparable to methanol.

Confirmed presence of organic molecules with two oxygen atoms in disks.

Abstract

The formation of asteroids, comets and planets occurs in the interior of protoplanetary disks during the early phase of star formation. Consequently, the chemical composition of the disk might shape the properties of the emerging planetary system. In this context, it is crucial to understand whether and what organic molecules are synthesized in the disk. In this Letter, we report the first detection of formic acid (HCOOH) towards the TW Hydrae protoplanetary disk. The observations of the trans-HCOOH 6$_{(1,6)-5(1,5)}$ transition were carried out at 129~GHz with ALMA. We measured a disk-averaged gas-phase t-HCOOH column density of $\sim$ (2-4)$\times$10$^{12}$~cm$^{-2}$, namely as large as that of methanol. HCOOH is the first organic molecules containing two oxygen atoms detected in a protoplanetary disk, a proof that organic chemistry is very active even though difficult to observe in these objects. Specifically, this simplest acid stands as the basis for synthesis of more complex carboxylic acids used by life on Earth.