Titan’s temporal evolution in stratospheric trace gases near the poles

Coustenis, A.; Jennings, Donald E.; Achterberg, R. K.; Bampasidis, G.; Lavvas, P.; Nixon, C. A.; Teanby, N. A.; Anderson, C. M.; Cottini, V.; Flasar, F. M.

doi:10.1016/j.icarus.2015.08.027

Cited by 49 publications

(113 citation statements)

References 31 publications

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“…The new calibration provides a better sensitivity for line detection and the enhanced radiance in some of the parts of the FP3 spectrum allows for a more precise inference of the abundances and their variation with time for some of the weaker species. The difference in the results still remains within the 10%-15% range with respect to the abundances published in Coustenis et al (2016).…”

Section: Observations and Analysismentioning

confidence: 45%

“…We have already published an analysis of spectra acquired by Cassini/CIRS at high resolution from 2010 onward, both in nadir and limb mode and at high and middle latitudes (Coustenis et al 2013(Coustenis et al , 2016. In our 2016 work, we showed that the hydrocarbons found at high concentrations and longer lifetimes did not show significant latitudinal variability in the past years and until mid-2013.…”

Section: Introductionmentioning

confidence: 64%

“…In particular, this Letter follows the Coustenis et al (2016) work on seasonal effects in the atmosphere, looking for the expected decrease in abundance of the northern pole constituents, not previously observed.…”

Section: Introductionmentioning

confidence: 84%

“…The selections that were already analyzed in Coustenis et al (2016) are re-investigated here with spectra from an updated calibration. This concerns the 2012 June and 2013 May southern averages and the 2013 December-2014 September northern averages.…”

Section: Observations and Analysismentioning

confidence: 99%

“…The temperature profile is originally set to the one measured at altitudes 0-147 km by the Huygens Atmospheric Structure Instrument (HASI; Fulchignoni et al 2005). Adjustments were applied to the HASI profile to extend in altitude and to account for latitude dependences and seasonal variations in temperature as found by CIRS emission values in the 7.7 μm CH 4 band and from lower-resolution observations (Coustenis et al 2007(Coustenis et al , 2010(Coustenis et al , 2016Achterberg et al 2008Achterberg et al , 2011Bampasidis et al 2012). For more details on the method see the literature.…”

Section: Observations and Analysismentioning

confidence: 99%

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Seasonal Evolution of Titan's Stratosphere Near the Poles

Coustenis

Jennings

Achterberg

et al. 2018

ApJL

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In this Letter, we report the monitoring of seasonal evolution near Titan's poles. We find Titan's south pole to exhibit since 2010 a strong temperature decrease and a dramatic enhancement of several trace species such as complex hydrocarbons and nitriles (HC 3 N and C 6 H 6 in particular) previously only observed at high northern latitudes. This results from the seasonal change on Titan going from winter (2002) to summer (2017) in the north and, at the same time, the onset of winter in the south pole. During this transition period atmospheric components with longer chemical lifetimes linger in the north, undergoing slow photochemical destruction, while those with shorter lifetimes decrease and reappear in the south. An opposite effect was expected in the north, but not observed with certainty until now. We present here an analysis of high-resolution nadir spectra acquired by Cassini/Cassini Composite Infrared Spectrometer in the past years and describe the temperature and composition variations near Titan's poles. From 2013 until 2016, the northern polar region has shown a temperature increase of 10 K, while the south has shown a more significant decrease (up to 25 K) in a similar period of time. While the south polar region has been continuously enhanced since about 2012, the chemical content in the north is finally showing a clear depletion for most molecules only since 2015. This is indicative of a non-symmetrical response to the seasons in Titan's stratosphere that can set constraints on photochemical and GCM models.

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Section: Observations and Analysismentioning

confidence: 45%

Section: Introductionmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 84%

Section: Observations and Analysismentioning

confidence: 99%

Section: Observations and Analysismentioning

confidence: 99%

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Seasonal Evolution of Titan's Stratosphere Near the Poles

Coustenis

Jennings

Achterberg

et al. 2018

ApJL

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Titan's atmosphere and climate

2017

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Titan is the only moon with a substantial atmosphere, the only other thick N2 atmosphere besides Earth's, the site of extraordinarily complex atmospheric chemistry that far surpasses any other solar system atmosphere, and the only other solar system body with stable liquid currently on its surface. The connection between Titan's surface and atmosphere is also unique in our solar system; atmospheric chemistry produces materials that are deposited on the surface and subsequently altered by surface‐atmosphere interactions such as aeolian and fluvial processes resulting in the formation of extensive dune fields and expansive lakes and seas. Titan's atmosphere is favorable for organic haze formation, which combined with the presence of some oxygen‐bearing molecules indicates that Titan's atmosphere may produce molecules of prebiotic interest. The combination of organics and liquid, in the form of water in a subsurface ocean and methane/ethane in the surface lakes and seas, means that Titan may be the ideal place in the solar system to test ideas about habitability, prebiotic chemistry, and the ubiquity and diversity of life in the universe. The Cassini‐Huygens mission to the Saturn system has provided a wealth of new information allowing for study of Titan as a complex system. Here I review our current understanding of Titan's atmosphere and climate forged from the powerful combination of Earth‐based observations, remote sensing and in situ spacecraft measurements, laboratory experiments, and models. I conclude with some of our remaining unanswered questions as the incredible era of exploration with Cassini‐Huygens comes to an end.

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Organic Ices in Titan’s Stratosphere

2018

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Titan's stratospheric ice clouds are by far the most complex of any observed in the solar system, with over a dozen organic vapors condensing out to form a suite of pure and co-condensed ices, typically observed at high winter polar latitudes. Once these stratospheric ices are formed, they will diffuse throughout Titan's lower atmosphere and most will eventually precipitate to the surface, where they are expected to contribute to Titan's regolith.Early and important contributions were first made by the InfraRed Interferometer Spectrometer (IRIS) on Voyager 1, followed by notable contributions from IRIS' successor, the Cassini Composite InfraRed Spectrometer (CIRS), and to a lesser extent, from Cassini's Visible and Infrared Mapping Spectrometer (VIMS) and the Imaging Science Subsystem (ISS) instruments. All three remote sensing instruments made new ice cloud discoveries, combined with monitoring the seasonal behaviors and time evolution throughout Cassini's 13-year mission tenure.A significant advance by CIRS was the realization that co-condensing chemical compounds can account for many of the CIRS-observed stratospheric ice cloud spectral features, especially for some that were previously puzzling, even though some of the observed spectral features are still not well understood. Relevant laboratory transmission spectroscopy efforts began just after the Voyager encounters, and have accelerated in the last few years due Ices in the Solar System Edited by

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Titan’s temporal evolution in stratospheric trace gases near the poles

Abstract: We analyze spectra acquired by the Cassini/Composite Infrared Spectrometer (CIRS) at high resolution from

Cited by 49 publications

References 31 publications

Seasonal Evolution of Titan's Stratosphere Near the Poles

Seasonal Evolution of Titan's Stratosphere Near the Poles

Titan's atmosphere and climate

Organic Ices in Titan’s Stratosphere

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