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Characterization of Titan’s Ontario Lacus region from Cassini/VIMS observations

2010-12Journal article Open access
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datacite.subject.fosCiências Naturais::Ciências Físicas
datacite.subject.fosCiências Naturais::Ciências da Terra e do Ambiente
dc.contributor.authorMoriconi, M. L.
dc.contributor.authorLunine, J. I.
dc.contributor.authorAdriani, A.
dc.contributor.authorD’Aversa, E.
dc.contributor.authorNegrão, A.
dc.contributor.authorFilacchione, G.
dc.contributor.authorCoradini, A.
dc.date.accessioned2025-11-05T18:26:54Z
dc.date.available2025-11-05T18:26:54Z
dc.date.issued2010-12
dc.description.abstractLiquid hydrocarbons were long predicted on Titan's surface before the RADAR instrument onboard Cassini detected lakes poleward of 70°N in July 2006. Before that the Cassini Imaging Science Subsystem (ISS) observed a lake-like feature in the South Pole, named Ontario Lacus, in July 2004. Here we analyze one observation of Ontario Lacus taken by the Visual and Infrared Mapping Spectrometer (VIMS) on 2007 December 5, during the T 38 flyby. This is the best spatially resolved image of a Titan lake to date by an imaging spectrometer, and has been previously reported in Brown et al. (Brown, R.H., Soderblom, L.A., Soderblom, J.M., Clark, R.N., Jaumann, R., Barnes, J.W., Sotin, C., Buratti, B., Baines, K.H., Nicholson, P.D. [2008]. Nature 454, 607-610) and in Barnes et al. (Barnes, J.W. et al. [2009]. Icarus 201, 217-225). The observing geometry and our data processing will be explained, followed by a discussion of the main characteristics of the image. The analyzed image covers a small portion of Ontario Lacus and shows what appears from RADAR data to be a region of modest slope (" ramp" ) adjacent to the dark lake itself. Our analysis of 5.0 μm spectral data suggests that the previously reported absorption feature of ethane seen at shorter wavelengths may be produced by damp sediments adjacent to the main liquid basin. The latter appears to be absorbing all of the photons incident upon it in the 5 μm spectral region and shows no discernible absorption features. A characterization of the basin composition and morphology is developed with the help of ISS and RADAR observations. The simplest model consistent with the data is an optically deep lake surrounded by a region in which ethane, propane, possibly methane, and other, less volatile hydrocarbons and nitriles are present mixed into spectroscopically neutral sediments. The dominance of relatively low vapor pressure organics outside the lake itself suggests a retreat of Ontario Lacus associated with evaporation on seasonal or longer timescales, consistent with analysis of RADAR and ISS images.eng
dc.description.sponsorshipWe thank F. Tosi, by IFSI–INAF, for his comments regarding the surface classification. We thank the VIMS and ISS teams for planning and operations. This research has been supported by the Italian Space Agency (ASI), the Cassini Project (NASA), and the program ‘‘Incentivazione alla mobilita’ di studiosi stranieri e italiani residenti all’estero.”
dc.identifier.citationM.L. Moriconi, J.I. Lunine, A. Adriani, E. D’Aversa, A. Negrão, G. Filacchione, A. Coradini, Characterization of Titan’s Ontario Lacus region from Cassini/VIMS observations, Icarus, Volume 210, Issue 2, 2010, Pages 823-831, ISSN 0019-1035, https://doi.org/10.1016/j.icarus.2010.07.023.
dc.identifier.doi10.1016/j.icarus.2010.07.023
dc.identifier.eissn1090-2643
dc.identifier.issn0019-1035
dc.identifier.urihttp://hdl.handle.net/10400.8/14534
dc.language.isoeng
dc.peerreviewedyes
dc.publisherElsevier
dc.relation.hasversionhttps://www.sciencedirect.com/science/article/pii/S0019103510003015?via%3Dihub
dc.relation.ispartofIcarus
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectTitan
dc.subjectSatellites
dc.subjectSurfaces
dc.subjectInfrared observations
dc.subjectImage processing
dc.titleCharacterization of Titan’s Ontario Lacus region from Cassini/VIMS observationseng
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage831
oaire.citation.issue2
oaire.citation.startPage823
oaire.citation.titleIcarus
oaire.citation.volume210
oaire.versionhttp://purl.org/coar/version/c_970fb48d4fbd8a85
person.familyNameNegrão
person.givenNameAlberto
person.identifier.orcid0000-0001-6042-1294
relation.isAuthorOfPublicationa4249a82-1904-4218-90fa-158b5c904c01
relation.isAuthorOfPublication.latestForDiscoverya4249a82-1904-4218-90fa-158b5c904c01

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Liquid hydrocarbons were long predicted on Titan's surface before the RADAR instrument onboard Cassini detected lakes poleward of 70°N in July 2006. Before that the Cassini Imaging Science Subsystem (ISS) observed a lake-like feature in the South Pole, named Ontario Lacus, in July 2004. Here we analyze one observation of Ontario Lacus taken by the Visual and Infrared Mapping Spectrometer (VIMS) on 2007 December 5, during the T 38 flyby. This is the best spatially resolved image of a Titan lake to date by an imaging spectrometer, and has been previously reported in Brown et al. (Brown, R.H., Soderblom, L.A., Soderblom, J.M., Clark, R.N., Jaumann, R., Barnes, J.W., Sotin, C., Buratti, B., Baines, K.H., Nicholson, P.D. [2008]. Nature 454, 607-610) and in Barnes et al. (Barnes, J.W. et al. [2009]. Icarus 201, 217-225). The observing geometry and our data processing will be explained, followed by a discussion of the main characteristics of the image. The analyzed image covers a small portion of Ontario Lacus and shows what appears from RADAR data to be a region of modest slope (" ramp" ) adjacent to the dark lake itself. Our analysis of 5.0 μm spectral data suggests that the previously reported absorption feature of ethane seen at shorter wavelengths may be produced by damp sediments adjacent to the main liquid basin. The latter appears to be absorbing all of the photons incident upon it in the 5 μm spectral region and shows no discernible absorption features. A characterization of the basin composition and morphology is developed with the help of ISS and RADAR observations. The simplest model consistent with the data is an optically deep lake surrounded by a region in which ethane, propane, possibly methane, and other, less volatile hydrocarbons and nitriles are present mixed into spectroscopically neutral sediments. The dominance of relatively low vapor pressure organics outside the lake itself suggests a retreat of Ontario Lacus associated with evaporation on seasonal or longer timescales, consistent with analysis of RADAR and ISS images.
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