Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
Methane and its isotopologues on Saturn from Cassini/CIRS observations
Ist Teil von
Icarus (New York, N.Y. 1962), 2009-02, Vol.199 (2), p.351-367
Ort / Verlag
Amsterdam: Elsevier Inc
Erscheinungsjahr
2009
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
High spectral resolution observations from the Cassini Composite Infrared Spectrometer [Flasar, F.M., and 44 colleagues, 2004. Space Sci. Rev. 115, 169–297] are analysed to derive new estimates for the mole fractions of CH
4, CH
3D and
13CH
4 of
(
4.7
±
0.2
)
×
10
−3
,
(
3.0
±
0.2
)
×
10
−7
and
(
5.1
±
0.2
)
×
10
−5
respectively. The mole fractions show no hemispherical asymmetries or latitudinal variability. The analysis combines data from the far-IR methane rotational lines and the mid-IR features of methane and its isotopologues, using both the correlated-
k retrieval algorithm of Irwin et al. [Irwin, P., and 9 colleagues, 2008. J. Quant. Spectrosc. Radiat. Trans. 109, 1136–1150] and a line-by-line approach to evaluate the reliability of the retrieved quantities. C/H was found to be enhanced by
10.9
±
0.5
times the solar composition of Grevesse et al. [Grevesse, N., Asplund, M., Sauval, A., 2007. Space Sci. Rev. 130 (1), 105–114],
2.25
±
0.55
times larger than the enrichment on Jupiter, and supporting the increasing fractional core mass with distance from the Sun predicted by the core accretion model of planetary formation. A comparison of the jovian and saturnian C/N, C/S and C/P ratios suggests different reservoirs of the trapped volatiles in a primordial solar nebula whose composition varies with distance from the Sun. This is supported by our derived D/H ratio in methane of
(
1.6
±
0.2
)
×
10
−5
, which appears to be smaller than the jovian value of Lellouch et al. [Lellouch, E., Bézard, B., Fouchet, T., Feuchtgruber, H., Encrenaz, T., de Graauw, T., 2001. Astron. Astrophys. 370, 610–622]. Mid-IR emission features provided an estimate of
C
12
/
C
13
=
91.8
−7.8
+8.4
, which is consistent with both the terrestrial ratio and jovian ratio, suggesting that carbon was accreted from a shared reservoir for all of the planets.