Water vapor in Titan’s stratosphere from Cassini CIRS far-infrared spectra

Cottini, V.; Nixon, C. A.; Jennings, Donald E.; Anderson, C. M.; Gorius, N.; Bjoraker, G. L.; Coustenis, A.; Teanby, N. A.; Achterberg, R. K.; Bézard, Bruno; Kok, Remco de; Lellouch, E.; Irwin, Patrick; Flasar, F. M.; Bampasidis, G.

doi:10.1016/j.icarus.2012.06.014

Cited by 42 publications

(81 citation statements)

References 44 publications

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“…Our study aims at reproducing (i) the H 2 O vertical profiles in Moreno et al (2012) and Cottini et al (2012) with both chemical schemes, for H08 and L14; and (ii) the CO 2 stratospheric abundance from Cassini/CIRS data (de Kok et al 2007). Both Hörst et al (2008) and (Moreno et al 2012, who considered the H08 chemical scheme) concluded that the OH vs. H 2 O form of the water input is unimportant when fitting the stratospheric water abundance, since a balance is established between OH and H 2 O, due to the photolysis of water and reactions between OH and CH 3 or OH and CH 4 recycling water.…”

Section: Model Descriptionmentioning

confidence: 99%

“…We re-examined these issues with the new treatment of the UV transmission within the haze and the new chemical network (L14). For this, we computed steady-state solutions by fine-tuning the OH/H 2 O influx to match the available observations (HIFI+PACS in Moreno et al (2012) and Cassini/CIRS by Cottini et al (2012)). Table 4.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Following the original detection by ISO (Coustenis et al 1998), the presence of water vapor has been recently revived by measurements of the H 2 O vertical profile by both Cassini/CIRS (Cottini et al 2012) and Herschel/PACS and Herschel/HIFI (Moreno et al 2012) at Titan. These studies differed significantly in the amounts of H 2 O implied by typically a factor of 4−5 at 115 km.…”

Section: Introductionmentioning

confidence: 99%

“…They confirmed the essential conclusion of Moreno et al (2012) in that the measured H 2 O profile is inconsistent with the CO 2 abundance, although the disagreement was reduced to a factor of 4. Dobrijevic et al (2014) found that reconciliation was possible if water abundances reported by Cottini et al (2012) are correct instead; although in this situation and for an Enceladus source, their model tended to overpredict the thermospheric abundance of H 2 O when compared to the globally averaged upper limit determined by Cui et al (2009). Dobrijevic et al (2014) also find that the deposition altitude of the OH/H 2 O flux (750 km, which is representative of micrometeorite ablation, vs. the top of the atmosphere, which is characteristic A&A 566, A143 (2014) of an Enceladus source) influences the flux required to reproduce the observed H 2 O and CO 2 profiles and the abundance of secondary N-O and H-N-O species. In this work, by means of a time-dependent photochemical model, we explore in more details the scenario of a variable oxygen source at Titan to see whether it is a plausible explanation to the "H 2 O/CO 2 puzzle".…”

Section: Introductionmentioning

confidence: 99%

“…Dobrijevic et al (2014) also find that the deposition altitude of the OH/H 2 O flux (750 km, which is representative of micrometeorite ablation, vs. the top of the atmosphere, which is characteristic A&A 566, A143 (2014) of an Enceladus source) influences the flux required to reproduce the observed H 2 O and CO 2 profiles and the abundance of secondary N-O and H-N-O species. In this work, by means of a time-dependent photochemical model, we explore in more details the scenario of a variable oxygen source at Titan to see whether it is a plausible explanation to the "H 2 O/CO 2 puzzle". We consider both the H 2 O profiles derived from Cassini/CIRS (Cottini et al 2012) and from Herschel (Moreno et al 2012). In addition, we study a scenario when Titan might have suffered a cometary impact in the past by bringing oxygen species into its atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O

Lara

Lellouch

González

et al. 2014

A&A

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Context. Titan's stratosphere contains oxygen compounds (CO, CO 2 , and H 2 O), implying an external source of oxygen whose nature is still uncertain. Recent observations from the Herschel Space Observatory using the HIFI and PACS instruments and the Cassini/CIRS, as well as steady-state photochemical modeling indicate that the amounts of CO 2 and H 2 O in Titan's stratosphere may imply inconsistent values of the OH/H 2 O input flux, and that the oxygen source is time-variable. Aims. We attempt to reconcile the H 2 O and CO 2 observed profiles in Titan's atmosphere by using an updated photochemical scheme and developing several time-dependent scenarios for the influx/evolution of oxygen species. Methods. We use a time-dependent photochemical model of Titan's atmosphere to calculate effective lifetimes and the response of Titan's oxygen compounds to changes in the oxygen input flux. Two variants for the C-H-O chemical network are considered. We investigate a time-variable Enceladus source and the evolution of material delivered by a cometary impact. Results. We find that the effective lifetime of H 2 O in Titan's atmosphere is only a factor of six shorter than that of CO 2 and exceeds 10 yr below 200 km. A time-variable Enceladus source, involving a decrease by a factor of 5-20 in the OH/H 2 O flux over the last few centuries, shows promise in explaining the relative CO 2 /H 2 O profiles. However, if the previous measurements from the Herschel Space Observatory are representative of Titan's atmospheric water, an additional H 2 O loss to the haze term is needed to bring the model in full agreement with the data. In an alternate situation, CO 2 production following a cometary impact that occurred at least 220-300 yr ago can in principle explain the CO 2 "excess" in Titan's stratosphere, but this scenario is highly unlikely, given the estimates of the impact rate at Titan.

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Section: Model Descriptionmentioning

confidence: 99%

Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O

Lara

Lellouch

González

et al. 2014

A&A

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Dissolution on Titan and on Earth: Toward the age of Titan's karstic landscapes

et al. 2015

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Titan's polar surface is dotted with hundreds of lacustrine depressions. Based on the hypothesis that they are karstic in origin, we aim at determining the efficiency of surface dissolution as a landshaping process on Titan, in a comparative planetology perspective with the Earth as reference. Our approach is based on the calculation of solutional denudation rates and allow inference of formation timescales for topographic depressions developed by chemical erosion on both planetary bodies. The model depends on the solubility of solids in liquids, the density of solids and liquids, and the average annual net rainfall rates. We compute and compare the denudation rates of pure solid organics in liquid hydrocarbons and of minerals in liquid water over Titan and Earth timescales. We then investigate the denudation rates of a superficial organic layer in liquid methane over one Titan year. At this timescale, such a layer on Titan would behave like salts or carbonates on Earth depending on its composition, which means that dissolution processes would likely occur, but would be 30 times slower on Titan compared to the Earth due to the seasonality of precipitation. Assuming an average depth of 100 m for Titan's lacustrine depressions, these could have developed in a few tens of millions of years at polar latitudes higher than 70 • N and S, and a few hundreds of million years at lower polar latitudes. The ages determined are consistent with the youth of the surface (< 1 Gyr) and the repartition of dissolution-related landforms on Titan.

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The Environment of Space Exploration

Nicogossian

2016

Space Physiology and Medicine

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Water vapor in Titan’s stratosphere from Cassini CIRS far-infrared spectra

Cited by 42 publications

References 44 publications

A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O

A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O

Dissolution on Titan and on Earth: Toward the age of Titan's karstic landscapes

The Environment of Space Exploration

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Water vapor in Titan’s stratosphere from Cassini CIRS far-infrared spectra

Cited by 42 publications

References 44 publications

A time-dependent photochemical model for Titan’s atmosphere and the origin of H2O

A time-dependent photochemical model for Titan’s atmosphere and the origin of H2O

Dissolution on Titan and on Earth: Toward the age of Titan's karstic landscapes

The Environment of Space Exploration

Contact Info

Product

Resources

About

A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O

A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O