The D/H Ratio in Methane in Titan: Origin and History

Mousis, O.; Gautier, D.; Coustenis, A.

doi:10.1006/icar.2002.6930

Cited by 83 publications

(73 citation statements)

References 50 publications

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“…This implies that Fischer-Tropsch catalysis did not modify the composition of ices produced in Saturn's subnebula. The methane observed in Titan most likely originates from the solar nebula gas-phase, as suggested by Mousis et al (2002) for interpreting the D:H ratio in CH 4 measured in its atmosphere, rather than having been produced in a catalytically-active region of Saturn's subnebula.…”

Section: Discussionmentioning

confidence: 91%

The role of Fischer-Tropsch catalysis in Jovian subnebular chemistry

Mousis¹,

Alibert

Sekine

et al. 2006

A&A

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We examine the production of methane via Fischer-Tropsch catalysis in an evolving turbulent model of the Jovian subnebula and its implications for the composition of satellitesimals produced in situ. We show that there is a catalytically-active region in the Jovian subnebula from 65 Jupiter radii that moves inwards with time. The pressure range in this region is about 10 −4 to 10 −3 bar and implies that, if transport processes and the cooling of the subnebula are not considered, CO and CO 2 are entirely converted into CH 4 via Fischer-Tropsch catalysis in about 10 1 -10 2 and 10 3 -10 4 years, respectively. On the other hand, the comparison of the chemical conversion times with the viscous timescale of the subdisk in the catalytically-active region implies that only CO can be fully converted into CH 4 , the conversion of CO 2 thus being restricted to a limited production of CH 4 . Moreover, the time required by the Jovian subnebula to cool down from the optimal temperature for Fischer-Tropsch catalysis to the condensation temperature of ices is at least two orders of magnitude higher than the viscous timescale. This implies that any CH 4 produced in the catalytically-active zone will be accreted onto Jupiter long before being incorporated into the forming ices. We then conclude that in an evolving turbulent subnebula, even if Fischer-Tropsch catalysis is active, it has no influence on the composition of the forming satellitesimals that will ultimately take part in the formation of regular icy satellites, in opposition to what has been expected from stationary models.

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Section: Discussionmentioning

confidence: 91%

The role of Fischer-Tropsch catalysis in Jovian subnebular chemistry

Mousis¹,

Alibert

Sekine

et al. 2006

A&A

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“…We have assumed f (R) = 31 at t = 0 for D/H in water. This value corresponds to that measured in the highly enriched component (D/H = (73 ± 12) × 10 −5 ) found in LL3 meteorites (Deloule et al 1998) which is compared to a protosolar value assumed to be equal to (2.35 ± 0.3) × 10 −5 (Mousis et al 2002b). The isotopic exchange between HDO and H 2 occurs as long as H 2 O remains in the vapor phase.…”

Section: Evolution Of the D/h Ratio In H 2 O In The Solar Nebulamentioning

confidence: 99%

“…Paper I proposed a scenario of the formation of Titan e-mail: Olivier.Mousis@obs-besancon.fr compatible with its current atmospheric molecular composition. Based on this scenario, Mousis et al (2002b) provided an interpretation of the CH 3 D/CH 4 ratio measured in the atmosphere of Titan. With a similar approach, Paper II estimated the per mass abundances of NH 3 , N 2 , CO and CH 4 with respect to H 2 O in the interiors of Ganymede and Callisto, thus providing an explanation for the suspected presence of ammonia in the subsurface oceans of these satellites.…”

Section: Introductionmentioning

confidence: 99%

An estimate of the D/H ratio in Jupiter and Saturn's regular icy satellites – Implications for the Titan Huygens mission

Mousis

2004

A&A

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Abstract. The solar nebula model described by Dubrulle (1993) and Drouart et al. (1999) is used to predict the D/H ratio in H 2 O ice of both Jovian and Saturnian regular satellite systems. These calculations take into account recent scenarios of formation of Jupiter and Saturn's large regular icy satellites developed from evolutionary turbulent models of the surrounding subnebulae. These scenarios argue that the Saturnian and Jovian subdisks were cold enough to prevent the vaporization of volatile species trapped in solids which produced the regular icy satellites. The hydrated solids formed in the feeding zones of Jupiter and Saturn during the cooling of the solar nebula. Hence, the D/H ratio in H 2 O ice of hydrated solids is likely the result of the isotopic exchange between HD and HDO which occurred in the solar nebula prior to the condensation of water. In these conditions, the D/H ratio in the regular icy satellites of Jupiter and Saturn is estimated to be between 3.8 and 4.7, and between 4.8 and 6.8 times the protosolar value, respectively. Such estimates, compared with subsequent in situ measurements of the D/H ratio in H 2 O ice of the Jovian and Saturnian regular satellite systems, should bring new constraints on the proposed scenarios of formation. This is the case with the Huygens probe mission which has the capacity of measuring the D/H ratio in the water ice which may exist on the surface of Titan.

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“…With respect to the D/H ratio in cometary methane, Aikawa & Herbst (1999) The prediction by Aikawa & Herbst (1999) is 3 orders of magnitude larger than the interpretation by Mousis et al (2002). Our infrared observation shows the 2 upper limit of 0.3 in the CH 3 D/CH 4 ratio.…”

Section: D/h Ratio In Methane Compared With Other Investigationsmentioning

confidence: 58%

Saturated Hydrocarbons in Comet 153P/Ikeya‐Zhang: Ethane, Methane, and Monodeuterio‐Methane

Kawakita¹,

Watanabe²,

Kinoshita³

et al. 2003

ApJ

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Emissions of the methane 3 band and the ethane 7 band were detected in the high-dispersion infrared spectra of comet 153P/Ikeya-Zhang taken by the Subaru Telescope with the Infrared Camera and Spectrograph (IRCS) on 2002 May 28 and 29 UT. The rotational temperature is estimated to be about 40-50 K from R 0 and R 1 lines of the methane 3 band. The production rates of methane and ethane were estimated by applying the rotational temperature of 50 K. Resultant production rates of methane and ethane are ð2:13 AE 0:40Þ Â 10 26 and ð1:75 AE 0:48Þ Â 10 26 molecules s À1 , respectively. The abundance ratio between ethane and methane is 0:82 AE 0:27, which is comparable with other comets within error bars. Although the emissions of monodeuterio-methane (CH 3 D) were searched for carefully, there is no evidence of them. The 2 (95% confidence) upper limit of the CH 3 D/CH 4 ratio is 0.3 in comet 153P/Ikeya-Zhang. Comparing the relative abundance of methane and ethane in the interstellar ices, we discussed the formation conditions of cometary nuclei.

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The D/H Ratio in Methane in Titan: Origin and History

Cited by 83 publications

References 50 publications

The role of Fischer-Tropsch catalysis in Jovian subnebular chemistry

The role of Fischer-Tropsch catalysis in Jovian subnebular chemistry

An estimate of the D/H ratio in Jupiter and Saturn's regular icy satellites – Implications for the Titan Huygens mission

Saturated Hydrocarbons in Comet 153P/Ikeya‐Zhang: Ethane, Methane, and Monodeuterio‐Methane

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