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

Abstract

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.

Deuterium Fractionation: The Ariadne’s Thread from the Precollapse Phase to Meteorites and Comets Today

“…In the warm ( 100-120 K) regions of the PSN, inside the snow-line, these ices sublimated. In general, PSN models aiming to model the fate of the ice (Drouart et al, 1999;Mousis et al, 2000;Mousis, 2004;Hersant et al, 2001;Horner et al, 2007Horner et al, , 2008Kavelaars et al, 2011) assumes that the PSN is a "diffusional" disk, in the sense that the turbulence is entirely responsible for its angular momentum transport. The first models used the simplest description for the disk provided by the famous α-viscosity 1D (vertical averaged) disk (Shakura & Sunyaev 1973).…”

Modeling the Jovian subnebula

“…On the basis of isotopic exchange calculations between HDO and H 2 in the solar nebula, Mousis (2004) estimated that the D:H ratio in Jovian regular icy satellites is between ∼4 and 5 times the solar value, assuming they were formed from planetesimals produced in Jupiter's feeding zone. On the other hand, icy satellites formed from planetesimals produced in the Jovian subnebula should present a lower D:H ratio in H 2 O ice since an additional isotopic exchange occurred between HDO and H 2 in the subdisk gas-phase.…”

Constraints from deuterium on the formation of icy bodies in the Jovian system and beyond

“…As discussed by Mousis (2004a), assuming that Jupiter and Saturn were formed at their current locations in the Solar system (Pollack et al, 1996), the plausible range of values of f in the solids produced in the feeding zones of both giant planets is covered by the vertical error bars in Fig.1. The value of f in H 2 O in ices produced in the feeding zone zone of Jupiter is thus between 3.8 and 4.7 times the Solar value.…”

“…Here, we summarise the works of Drouart et al (1999), Mousis et al (2000), Hersant et al (2001), Mousis (2004a) and Horner et al (2007) who described the evolution of the deuterium enrichment factor, f , in H 2 O within the Solar nebula. The calculations of these authors were based on the fact that the main reservoir of deuterium in the Solar nebula was molecular hydrogen (HD vs. H 2 ), and that ion-molecule reactions in the interstellar medium (see e.g.…”