Detection of hydrocarbons in Titan using high-resolution cross-correlation spectroscopy
Abstract
High-resolution cross-correlation spectroscopy (HRCCS) is a powerful technique for detecting molecules whose individual spectral lines are too weak to be identified directly, but its sensitivity is limited by the availability and quality of high-resolution opacity data. Many molecules of atmospheric and astrobiological interest lack complete line lists, restricting traditional template-based searches. In this work, we use Titan as a controlled testbed to develop and validate a new cross-section-based methodology for HRCCS template construction. We analyse K-band CRIRES+ observations of Titan (1.99 - 2.48 μm), and compute cross-correlation functions using both line-by-line and cross-section-based templates. Our analysis recovers known hydrocarbons such as methane (CH4) and acetylene (C2H2), and yields the first HRCCS detection of ethane (C2H6) with a significance of SNRpeak = 5.17 {\pm} 0.07. The ethane detection was made possible exclusively through cross-section-based templates, as no high-resolution line list currently exists for this molecule. These results demonstrate that cross-section-based template construction is a practical and powerful strategy for extending HRCCS to molecules that currently lack reliable line lists, and establish Titan as a benchmark for calibrating molecular detection techniques that can be applied to both solar system and exoplanet atmospheres. Future applications of this approach to other ground-based high-resolution spectrographs, as well as to JWST's highest-resolution modes and next-generation facilities such as the ELT, could significantly expand the inventory of molecules detectable in planetary atmospheres.
Versions
Related
- High-resolution transmission spectroscopy of KELT-18b. Metastable helium detection at 1083 nm
- High-resolution transmission spectroscopy of KELT-18b Metastable helium detection at 1083 nm
- Elastic Properties of Titan Tholins Revealed by Brillouin Spectroscopy
- Detection of Aliphatically Deuterated Aromatic Hydrocarbons in the Large Magellanic Cloud 30 Doradus Star-forming Complex
- Intermediate- and high-resolution optical spectroscopy on the nascent planetary nebula Vy 2-2: Evidence of binary-star evolution
BibTeX
@misc{coelho2026detection,
title = {{Detection of hydrocarbons in Titan using high-resolution cross-correlation spectroscopy}},
author = {Maria Coelho and Rafael Rianço-Silva and Diogo Gonçalves and Pedro Machado and Zita Martins},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03975},
eprint = {2609.03975},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03975},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Detection of hydrocarbons in Titan using high-resolution cross-correlation spectroscopy
AU - Maria Coelho
AU - Rafael Rianço-Silva
AU - Diogo Gonçalves
AU - Pedro Machado
AU - Zita Martins
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03975
UR - https://arxiv.org/abs/2609.03975
AB - High-resolution cross-correlation spectroscopy (HRCCS) is a powerful technique for detecting molecules whose individual spectral lines are too weak to be identified directly, but its sensitivity is limited by the availability and quality of high-resolution opacity data. Many molecules of atmospheric and astrobiological interest lack complete line lists, restricting traditional template-based searches. In this work, we use Titan as a controlled testbed to develop and validate a new cross-section-based methodology for HRCCS template construction. We analyse K-band CRIRES+ observations of Titan (1.99 - 2.48 μm), and compute cross-correlation functions using both line-by-line and cross-section-based templates. Our analysis recovers known hydrocarbons such as methane (CH4) and acetylene (C2H2), and yields the first HRCCS detection of ethane (C2H6) with a significance of SNRpeak = 5.17 {\pm} 0.07. The ethane detection was made possible exclusively through cross-section-based templates, as no high-resolution line list currently exists for this molecule. These results demonstrate that cross-section-based template construction is a practical and powerful strategy for extending HRCCS to molecules that currently lack reliable line lists, and establish Titan as a benchmark for calibrating molecular detection techniques that can be applied to both solar system and exoplanet atmospheres. Future applications of this approach to other ground-based high-resolution spectrographs, as well as to JWST's highest-resolution modes and next-generation facilities such as the ELT, could significantly expand the inventory of molecules detectable in planetary atmospheres.
ER -