[astro-ph.EP]. 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 {um), 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.
Maria Coelho, Rafael Rianço-Silva, Diogo Gonçalves, Pedro Machado, Zita Martins
Comments: Accepted for publication in RAS Techniques and Instruments on August 2026
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); Atmospheric and Oceanic Physics (physics.ao-ph); Space Physics (physics.space-ph)
Cite as: arXiv:2609.03975 [astro-ph.EP] (or arXiv:2609.03975v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2609.03975
Focus to learn more
Related DOI:
https://doi.org/10.1093/rasti/rzag068
Focus to learn more
Submission history
From: Rafael Rianço-Silva
[v1] Thu, 3 Sep 2026 15:12:56 UTC (8,544 KB)
https://arxiv.org/abs/2609.03975
Astrobiology, Astrochemistry, Astrogeology,
