Spectrophotometric evidence for a metal-bearing, carbonaceous, and pristine interstellar comet 3I/ATLAS

TL;DR

This study presents spectrophotometric evidence suggesting that interstellar comet 3I/ATLAS is a primitive, metal-rich, carbonaceous body with signs of aqueous alteration, cryovolcanism, and unique chemical processes, offering insights into distant minor bodies.

Contribution

It provides the first spectroscopic comparison of 3I/ATLAS with pristine carbonaceous chondrites, revealing its potential metal enrichment and primitive nature, and discusses its implications for understanding interstellar objects.

Findings

Spectral similarities to carbonaceous chondrites suggest primitive composition.

Evidence of aqueous alteration and cryovolcanism in 3I/ATLAS.

Metal-rich composition may lead to unique chemical reactions in the coma.

Abstract

3I/ATLAS is only the second confirmed cometary object known to enter the Solar System from interstellar space. Cosmogonic considerations suggest that this body may possess relatively high tensile strength and a substantial metal fraction. We present photometric observations along its inbound trajectory toward perihelion, together with a spectroscopic comparison to pristine carbonaceous chondrites from the NASA Antarctic collection. The spectral similarities indicate that 3I/ATLAS may be a primitive carbonaceous object, likely enriched in native metal and undergoing significant aqueous alteration during its approach to the Sun, experiencing cryovolcanism as we could expect for a pristine Trans-Neptunian Object. We propose that the combination of elevated metal abundance and abundant water ice can account for the unusual coma morphology and chemical products reported to date. To do so, corrosion of fine-grained metal grains can originate energetic Fischer-Tropsch reactions, generating specific chemical products into the coma that are not so common in other comets because most of them formed in the outer solar system and didn't inherited so much metal. Interstellar objects such as 3I/ATLAS provide rare opportunities to investigate physical and chemical processes in distant minor bodies of our own Solar System, including trans-Neptunian objects and Oort Cloud comets.