Skip to content

Ethane in Titan's Stratosphere from Cassini CIRS Far- And Mid-infrared Spectra

Research output: Contribution to journalArticle

Original languageEnglish
Article number160
Number of pages10
JournalAstronomical Journal
Volume157
Issue number4
DOIs
DateAccepted/In press - 6 Mar 2019
DatePublished (current) - 2 Apr 2019

Abstract

The Cassini Composite Infrared Spectrometer (CIRS) observed thermal emission in the far- and mid-infrared (from 10 to 1500 cm-1), enabling spatiotemporal studies of ethane on Titan across the span of the Cassini mission from 2004 through 2017. Many previous measurements of ethane on Titan have relied on modeling the molecule's mid-infrared ν 12 band, centered on 822 cm-1. Other bands of ethane at shorter and longer wavelengths were seen, but have not been modeled to measure ethane abundance. Spectral line lists of the far-infrared ν 4 torsional band at 289 cm-1 and the mid-infrared ν 8 band centered at 1468 cm-1 have recently been studied in the laboratory. We model CIRS observations of each of these bands (along with the ν 12 band) separately and compare the retrieved mixing ratios from each spectral region. Nadir observations of the ν 4 band probe the low stratosphere below 100 km. Our equatorial measurements at 289 cm-1 show an abundance of (1.0 ±0.4) ×10-5 at 88 km from 2007 to 2017. This mixing ratio is consistent with measurements at higher altitudes, in contrast to the depletion that many photochemical models predict. Measurements from the ν 12 and ν 8 bands are comparable to each other, with the ν 12 band probing an altitude range that extends deeper in the atmosphere. We suggest that future studies of planetary atmospheres may observe the ν 8 band, enabling shorter wavelength studies of ethane. There may also be an advantage to observing both the ethane ν 8 band and nearby methane ν 4 band in the same spectral window.

    Research areas

  • infrared: planetary systems, planets and satellites: atmospheres, planets and satellites: individual (Titan)

Download statistics

No data available

Documents

Documents

  • Full-text PDF (final published version)

    Rights statement: This is the final published version of the article (version of record). It first appeared online via American Astronomical Society at https://iopscience.iop.org/article/10.3847/1538-3881/ab0e07 . Please refer to any applicable terms of use of the publisher.

    Final published version, 1.6 MB, PDF document

DOI

View research connections

Related faculties, schools or groups