Interstellar Comet 3I/ATLAS: Evidence for Galactic Cosmic-Ray Processing
| dc.contributor.author | Maggiolo, R. | |
| dc.contributor.author | Dhooghe, F. | |
| dc.contributor.author | Gronoff, G.P. | |
| dc.contributor.author | De Keyser, J. | |
| dc.contributor.author | Cessateur, G. | |
| dc.date | 2026 | |
| dc.date.accessioned | 2026-01-13T13:08:58Z | |
| dc.date.available | 2026-01-13T13:08:58Z | |
| dc.identifier.uri | https://orfeo.belnet.be/handle/internal/14527 | |
| dc.description | Spectral observations of 3I/ATLAS (C/2025 N1) with JWST/NIRSpec and SPHEREx reveal an extreme CO2 enrichment (CO2/H2O = 7.6 ± 0.3) that is 4.5σ above solar system comet trends and among the highest ever recorded. This unprecedented composition, combined with substantial absolute CO levels (CO/H2O = 1.65 ± 0.09) and red spectral slopes, provides direct evidence for galactic cosmic-ray (GCR) processing of the outer layers of the interstellar comet nucleus. Laboratory experiments demonstrate that GCR irradiation efficiently converts CO to CO2 while synthesizing organic-rich crusts, suggesting that the outer layers of 3I/ATLAS consist of irradiated material whose properties are consistent with the observed composition of the 3I/ATLAS coma and with its observed spectral reddening. Estimates of the erosion rate of 3I/ATLAS indicate that current outgassing samples the GCR-processed zone only (depth ∼15–20 m), never reaching pristine interior material. Outgassing of pristine material after perihelion remains possible, though it is considered unlikely. This points to a paradigm shift: long-residence interstellar objects likely reveal primarily GCR-processed material rather than pristine material representative of their primordial formation environments. With 3I/ATLAS approaching perihelion in 2025 October, immediate follow-up observations are critical to confirm this interpretation and establish GCR processing as a fundamental evolutionary pathway for interstellar objects. | |
| dc.language | eng | |
| dc.title | Interstellar Comet 3I/ATLAS: Evidence for Galactic Cosmic-Ray Processing | |
| dc.type | Article | |
| dc.subject.frascati | Physical sciences | |
| dc.audience | Scientific | |
| dc.subject.free | Interstellar objects | |
| dc.subject.free | Comets | |
| dc.subject.free | Comet nuclei | |
| dc.subject.free | Cosmic rays | |
| dc.subject.free | Galactic cosmic rays | |
| dc.source.title | The Astrophysical Journal Letters | |
| dc.source.volume | 996 | |
| dc.source.issue | 2 | |
| dc.source.page | L34 | |
| Orfeo.peerreviewed | Yes | |
| dc.identifier.doi | 10.3847/2041-8213/ae2fff | |
| dc.identifier.url |