C2N2 vertical profile in Titan’s stratosphere

Journal article

In this paper, we present the first measurements of the vertical distribution of cyanogen (${{\rm{C}}}_{2}{{\rm{N}}}_{2}$) in Titan's lower atmosphere at different latitudes and seasons, using Cassini's Composite Infrared Spectrometer far-infrared data. We also study the vertical distribution of three other minor species detected in our data: methylacetylene (${{\rm{C}}}_{3}{{\rm{H}}}_{4}$), diacetylene (${{\rm{C}}}_{4}{{\rm{H}}}_{2}$), and ${{\rm{H}}}_{2}{\rm{O}}$, in order to compare them to ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$, but also to get an overview of their seasonal and meridional variations in Titan's lower stratosphere from 85 km to 225 km. We measured an average volume mixing ratio of ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ of $6.2\pm 0.8\times {10}^{-11}$ at 125 km at the equator, but poles exhibit a strong enrichment in ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ (up to a factor 100 compared to the equator), greater than what was measured for ${{\rm{C}}}_{3}{{\rm{H}}}_{4}$ or ${{\rm{C}}}_{4}{{\rm{H}}}_{2}$. Measuring ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ profiles provides constraints on the processes controlling its distribution, such as bombardment by Galactic Cosmic Rays which seem to have a smaller influence on ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ than predicted by photochemical models.

Authors: Sylvestre, M; Teanby, N; Dobrijevic, M; Sharkey, J; Irwin, PGJ

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: Astronomical Journal
• Volume: 160
• Issue: 4
• Article number: 178
• Publication date: 2020-09-21
• Acceptance date: 2020-08-12
• DOI: 10.3847/1538-3881/abafb2
• EISSN: 1538-3881
• ISSN: 0004-6256
• Language: English
• Keywords: Saturnian satellites; FFR; atmospheric variability; far infrared astronomy; atmospheric composition; spectroscopy; planetary atmospheres