Ethane in Titan’s Stratosphere from Cassini CIRS Far- and Mid-infrared Spectra

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dc.contributor.authorLombardo, Nicholas A.
dc.contributor.authorNixon, Conor A.
dc.contributor.authorSylvestre, Melody
dc.contributor.authorJennings, Donald E.
dc.contributor.authorTeanby, Nicholas
dc.contributor.authorIrwin, Patrick J. G.
dc.contributor.authorFlasar, F. Michael
dc.date.accessioned2019-04-19T20:03:10Z
dc.date.available2019-04-19T20:03:10Z
dc.date.issued2019-04-02
dc.description.abstractThe 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 ν₁₂ 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 ν₄ torsional band at 289 cm⁻¹ and the mid-infrared ν₈ 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 ν12 band) separately and compare the retrieved mixing ratios from each spectral region. Nadir observations of the ν₄ 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 ν₁₂ and ν₈ bands are comparable to each other, with the ν₁₂ band probing an altitude range that extends deeper in the atmosphere. We suggest that future studies of planetary atmospheres may observe the ν₈ band, enabling shorter wavelength studies of ethane. There may also be an advantage to observing both the ethane ν₈ band and nearby methane ν₄ band in the same spectral windowen_US
dc.description.sponsorshipN.A.L. was supported by NASA through the CRESST II cooperative agreement CA 80GSFC17M0002. N.A.L., C.A.N., R.K.A., and F.M.F. were supported by the NASA Cassini Project for the research work reported in this paper. M.S., N.A.T., and P.G.J.I. were funded by the UK Science and Technology Facilities Council.en_US
dc.description.urihttps://ora.ox.ac.uk/objects/uuid:f8e99d43-f06a-47d6-9636-6721cd477050/download_file?file_format=pdf&safe_filename=Lombardo_etal_2019_Ethane_in_Titans_stratosphere_from.pdf&type_of_work=Recorden_US
dc.format.extent10 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2eqz0-0pbg
dc.identifier.citationNicholas A. Lombardo, et.al, Ethane in Titan’s Stratosphere from Cassini CIRS Far- and Mid-infrared Spectra, The Astronomical Journal, 157:160 (10pp), 2019 April, https://doi.org/10.3847/1538-3881/ab0e07en_US
dc.identifier.urihttps://doi.org/10.3847/1538-3881/ab0e07
dc.identifier.urihttp://hdl.handle.net/11603/13477
dc.language.isoen_USen_US
dc.publisherThe American Astronomical Societyen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
dc.subjectinfrared: planetary systemsen_US
dc.subjectplanets and satellites: atmospheresen_US
dc.subjectplanets and satellites: individual (Titan)en_US
dc.titleEthane in Titan’s Stratosphere from Cassini CIRS Far- and Mid-infrared Spectraen_US
dc.typeTexten_US

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