J/A+A/666/A140ivo://CDS.VizieR/J/A+A/666/A140doi:10.26093/cds/vizier.36660140CDSRannou P.Coutelier M.Rey M.Vinatier S.2023-07-03T14:34:42Z2022-10-19T09:13:38ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsolar-systemsolar-system-planetsTitan, the largest satellite of Saturn, has a dense atmosphere mainly composed of nitrogen, methane at a percent level, and minor species. It is also covered by a thick and global photochemical organic haze. In the last two decades, the observations made by the Cassini orbiter and the Huygens probe have greatly improved our knowledge of Titan's system. The surface, haze, clouds, and chemical species can be studied and characterised with several instruments simultaneously. On the other hand, some compounds of its climatic cycle remain poorly known. This is clearly the case of the methane cycle, which is, however, a critical component of Titan's climate and of its evolution.We reanalysed four solar occultations by Titan's atmosphere observed with the infrared part of the Visual Infrared Mapping Spectrometer (VIMS) instrument. These observations were already analysed, but here we used significantly improved methane spectroscopic data. We retrieved the haze properties (not treated previously) and the mixing ratios of methane, deuterated methane, and CO in the stratosphere and in the low mesosphere. The methane mixing ratio in the stratosphere is much lower (about 1.1%) than expected from Huygens measurements (about 1.4 to 1.5%). This is consistent with previous results obtained with other instruments. However, features in the methane vertical profiles clearly demonstrate that there are interactions between the methane distribution and the atmosphere circulation. We also retrieved the haze extinction profiles and the haze spectral behaviour. We find that aerosols are aggregates with a fractal dimension of Df=~2.3+/-0.1, rather than Df=~2 as previously thought. Our analysis also reveals noticeable changes in their size distribution and their morphology with altitude and time. These changes are also clearly connected to the atmosphere circulation and concerns the whole stratosphere and the transition between the main and the detached haze layers. We finally display the vertical profiles of CH_3_D and CO for the four observations. Although the latter retrievals have large error bars due to noisy data, we could derive values in agreement with other works.2022A&A...666A.140Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/666/A140CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/666/A140https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/666/A140http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/666/A140https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/666/A140https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/666/A140http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/666/A140GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/666/A140/et10eHaze extinction at three wavelengths retrieved with occultation T10E (Figure 9 and 18) (kext_T10E.dat)AltAltitudekmpos.earth.altitude;instr.obstyfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintExt884Extinction at 884nmm**-1obs.atmos.extinctiondoublee_Ext884Lower value of extinction at 884nm errorm**-1stat.errordoubleE_Ext884Upper value of extinction at 884nm errorm**-1stat.error;stat.maxdoubleExt1540Extinction at 1540nmm**-1obs.atmos.extinctiondoublee_Ext1540Lower value of extinction at 1540nm errorm**-1stat.errordoubleE_Ext1540Upper value of extinction at 1540nm errorm**-1stat.error;stat.maxdoubleExt2199Extinction at 2199nmm**-1obs.atmos.extinctiondoublee_Ext2199Lower value of extinction at 2199nm errorm**-1stat.errordoubleE_Ext2199Upper value of extinction at 2199nm errorm**-1stat.error;stat.maxdoubleJ/A+A/666/A140/et10elwHaze extinction at wavelength 4898nm retrieved with occultation T10E (Figure 18) (kext_T10E_LW.dat)AltAltitudekmpos.earth.altitude;instr.obstyfloate_Ext4989Lower value of extinction at 4989nm errorm**-1stat.errordoubleE_Ext4989Upper value of extinction at 4989nm errorm**-1stat.error;stat.maxdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintExt4989Extinction at 4989nmm**-1obs.atmos.extinctiondoubleJ/A+A/666/A140/et53eHaze extinction at three wavelengths retrieved with occultation T53E (Figure 9 and 18) (kext_T53E.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatExt884Extinction at 884nmm**-1obs.atmos.extinctiondoublee_Ext884Lower value of extinction at 884nm errorm**-1stat.errordoubleE_Ext884Upper value of extinction at 884nm errorm**-1stat.error;stat.maxdoubleExt1540Extinction at 1540nmm**-1obs.atmos.extinctiondoublee_Ext1540Lower value of extinction at 1540nm errorm**-1stat.errordoubleE_Ext1540Upper value of extinction at 1540nm errorm**-1stat.error;stat.maxdoubleExt2199Extinction at 2199nmm**-1obs.atmos.extinctiondoublee_Ext2199Lower value of extinction at 2199nm errorm**-1stat.errordoubleE_Ext2199Upper value of extinction at 2199nm errorm**-1stat.error;stat.maxdoubleJ/A+A/666/A140/et53elwHaze extinction at wavelength 4898nm retrieved with occultation T53E (Figure 18) (kext_T53E_LW.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatExt4989Extinction at 4989nmm**-1obs.atmos.extinctiondoublee_Ext4989Lower value of extinction at 4989nm errorm**-1stat.errordoubleE_Ext4989Upper value of extinction at 4989nm errorm**-1stat.error;stat.maxdoubleJ/A+A/666/A140/et78eHaze extinction at three wavelengths retrieved with occultation T78E (Figure 9 and 18) (kext_T78E.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatExt884Extinction at 884nmm**-1obs.atmos.extinctiondoublee_Ext884Lower value of extinction at 884nm errorm**-1stat.errordoubleE_Ext884Upper value of extinction at 884nm errorm**-1stat.error;stat.maxdoubleExt1540Extinction at 1540nmm**-1obs.atmos.extinctiondoublee_Ext1540Lower value of extinction at 1540nm errorm**-1stat.errordoubleE_Ext1540Upper value of extinction at 1540nm errorm**-1stat.error;stat.maxdoubleExt2199Extinction at 2199nmm**-1obs.atmos.extinctiondoublee_Ext2199Lower value of extinction at 2199nm errorm**-1stat.errordoubleE_Ext2199Upper value of extinction at 2199nm errorm**-1stat.error;stat.maxdoubleJ/A+A/666/A140/et78elwHaze extinction at wavelength 4898nm retrieved with occultation T78E (Figure 18) (kext_T78E_LW.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatExt4989Extinction at 4989nmm**-1obs.atmos.extinctiondoublee_Ext4989Lower value of extinction at 4989nm errorm**-1stat.errordoubleE_Ext4989Upper value of extinction at 4989nm errorm**-1stat.error;stat.maxdoubleJ/A+A/666/A140/et78iHaze extinction at three wavelengths retrieved with occultation T78I (Figure 9 and 18) (kext_T78I.dat)e_Ext1540Lower value of extinction at 1540nm errorm**-1stat.errordoubleE_Ext1540Upper value of extinction at 1540nm errorm**-1stat.error;stat.maxdoublee_Ext2199Lower value of extinction at 2199nm errorm**-1stat.errordoubleE_Ext2199Upper value of extinction at 2199nm errorm**-1stat.error;stat.maxdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatExt884Extinction at 884nmm**-1obs.atmos.extinctiondoublee_Ext884Lower value of extinction at 884nm errorm**-1stat.errordoubleE_Ext884Upper value of extinction at 884nm errorm**-1stat.error;stat.maxdoubleExt1540Extinction at 1540nmm**-1obs.atmos.extinctiondoubleExt2199Extinction at 2199nmm**-1obs.atmos.extinctiondoubleJ/A+A/666/A140/et78ilwHaze extinction at wavelength 4898nm retrieved with occultation T78I (Figure 18) (kext_T78I_LW.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatExt4989Extinction at 4989nmm**-1obs.atmos.extinctiondoublee_Ext4989Lower value of extinction at 4989nm errorm**-1stat.errordoubleE_Ext4989Upper value of extinction at 4989nm errorm**-1stat.error;stat.maxdoubleJ/A+A/666/A140/eslt10eHaze spectral slope dLn(kext)/dLn(wavelength) relative to alpha_0 = -2.18 retrieved with occultation T10E (Figure 10) (kext_slope_T10E.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitude (km)kmpos.earth.altitude;instr.obstyfloatExtslExtinction slope - 2.18obs.atmos.extinctiondoublee_Extsl[] Lower value of extinction slope - 2.18 errorstat.errordoubleE_Extsl[] Upper value of extinction slope - 2.18 errorstat.error;stat.maxdoubleJ/A+A/666/A140/eslt53eHaze spectral slope dLn(kext)/dLn(wavelength) relative to alpha_0 = -2.18 retrieved with occultation T53E (Figure 10) (kext_slope_T53E.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitude (km)kmpos.earth.altitude;instr.obstyfloatExtslExtinction slope - 2.18obs.atmos.extinctiondoublee_Extsl[] Lower value of extinction slope - 2.18 errorstat.errordoubleE_Extsl[] Upper value of extinction slope - 2.18 errorstat.error;stat.maxdoubleJ/A+A/666/A140/eslt78eHaze spectral slope dLn(kext)/dLn(wavelength) relative to alpha_0 = -2.18 retrieved with occultation T78E (Figure 10) (kext_slope_T78E.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitude (km)kmpos.earth.altitude;instr.obstyfloatExtslExtinction slope - 2.18obs.atmos.extinctiondoublee_Extsl[] Lower value of extinction slope - 2.18 errorstat.errordoubleE_Extsl[] Upper value of extinction slope - 2.18 errorstat.error;stat.maxdoubleJ/A+A/666/A140/eslt78iHaze spectral slope dLn(kext)/dLn(wavelength) relative to alpha_0 = -2.18 retrieved with occultation T78I (Figure 10) (kext_slope_T78I.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitude (km)kmpos.earth.altitude;instr.obstyfloatExtslExtinction slope - 2.18obs.atmos.extinctiondoublee_Extsl[] Lower value of extinction slope - 2.18 errorstat.errordoubleE_Extsl[] Upper value of extinction slope - 2.18 errorstat.error;stat.maxdoubleJ/A+A/666/A140/xch4t10eMethane mixing ratio retrieved with occultation T10E (Figure 11 - top) (xch4_T10E.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatCH4CH_4_ mole factionphys.abunddoublee_CH4Lower value of CH_4_ sigma mole faction errorstat.errordoubleE_CH4Lower value of CH_4_ sigma mole faction errorstat.error;stat.maxdoubleJ/A+A/666/A140/xch4t53eMethane mixing ratio retrieved with occultation T53E (Figure 11 - top) (xch4_T53E.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatCH4CH_4_ mole factionphys.abunddoublee_CH4Lower value of CH_4_ sigma mole faction errorstat.errordoubleE_CH4Lower value of CH_4_ sigma mole faction errorstat.error;stat.maxdoubleJ/A+A/666/A140/xch4t78eMethane mixing ratio retrieved with occultation T78E (Figure 11 - top) (xch4_T78E.dat)CH4CH_4_ mole factionphys.abunddoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloate_CH4Lower value of CH_4_ sigma mole faction errorstat.errordoubleE_CH4Lower value of CH_4_ sigma mole faction errorstat.error;stat.maxdoubleJ/A+A/666/A140/xch4t78iMethane mixing ratio retrieved with occultation T78I (Figure 11 - top) (xch4_T78I.dat)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltAltitudekmpos.earth.altitude;instr.obstyfloatCH4CH_4_ mole factionphys.abunddoublee_CH4Lower value of CH_4_ sigma mole faction errorstat.errordoubleE_CH4Lower value of CH_4_ sigma mole faction errorstat.error;stat.maxdouble