Nature and Source of Organic Matter in the Shoemaker–Levy 9 Jovian Impact Blemishes

Wilson, P. D.; Sagan, Carl

doi:10.1006/icar.1997.5783

Cited by 4 publications

(3 citation statements)

References 45 publications

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“…Since then, the role of these reactions in the solar nebula has been investigated by several groups (Lewis and Prinn, 1980;Hayatsu and Anders, 198 1 ;Mendybaev et al, 1986;Prinn and Fegley, 1989;Fegley, 1993Fegley, , 1997. These reactions are also thought to be important in the subnebulae in which the giant volatile materials that can be much more readily planets formed (Prinn andFegley, 1981, 1989;Fegley, 1998), in the circumstellar envelopes of oxygen-rich red giant stars (Kress, 1997), in the fireballs created by the impact of Comet Shoemaker-Levy 9 into Jupiter (Wilson and Sagan, 1997;Borunov et al, 1997), and in the aftermath of large impacts common during the formation of the terrestrial planets' atmospheres (Hayatsu and Anders,198 1). Also, these reactions are thought to have played a role in geological environments in which light hydrocarbons of abiogenic origin are found (Holm, 1996;Berndt et al, 1996;Salvi and Williams-Jones, 1997), in undersea hydrothermal vents (McCollom et al, 1999), and during terrestrial volcanism (Basiuk and NavarroGonzalez, 1996;Zolotov and Shock, 2000).…”

Section: Background and Motivationmentioning

confidence: 99%

The role of Fischer‐Tropsch catalysis in solar nebula chemistry

Kress

Tielens²

2001

Meteorit & Planetary Scien

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Abstract-Fischer-Tropsch catalysis, the ironhickel catalyzed conversion of CO and H2 to hydrocarbons, would have been the only thermally-driven pathway available in the solar nebula to convert CO into other forms of carbon. A major issue in meteoritics is to determine the origin of meteoritic organics: are they mainly formed from CO in the solar nebula via a process such as Fischer-Tropsch, or are they derived from interstellar organics? In order to determine the role that Fischer-Tropsch catalysis may have played in the organic chemical evolution of the solar nebula, we have developed a kinetic model for this process. Our model results agree well with experimental data from several existing laboratory studies. In contrast, empirical rate equations, which have been derived from experimental rate data for a limited temperature (7") and pressure (P) range, are inconsistent with experimental rate data for higher T and lower P.We have applied our model to pressure and temperature profiles for the solar nebula, during the epoch in which meteorite parent bodies condensed and agglomerated. We find that, under nebular conditions, the conversion rate of CO to CH4 does not simply increase with temperature as the empirically-derived equations suggest. Instead, our model results show that this process would have been most efficient in a fairly narrow region that coincides with the present position of the asteroid belt. Our results support the hypothesis that Fischer-Tropsch catalysis may have played a role in solar nebula chemistry by converting CO into less processed in the nebula and in parent bodies.

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Section: Background and Motivationmentioning

confidence: 99%

The role of Fischer‐Tropsch catalysis in solar nebula chemistry

Kress

Tielens²

2001

Meteorit & Planetary Scien

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“…Also, the ring was not visible at 2.3 µm, although a methane band occurs at that wavelength. This has prompted investigation of organic compounds such as tholins (Wilson & Sagan 1997). But many observations show (and our models agree) that the splashback took place at quite low pressure levels (less than tens of µbar).…”

Section: The 3-4-µm Ringmentioning

confidence: 61%

Models of the Shoemaker‐Levy 9 Impacts. II. Radiative‐Hydrodynamic Modeling of the Plume Splashback

Deming

Harrington

2001

ApJ

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We model the plume 'splashback' phase of the Shoemaker-Levy 9 (SL9) collisions with Jupiter. We modified the ZEUS-3D hydrodynamic code to include radiative transport in the gray approximation, and present validation tests. After initializing with a model Jovian atmosphere, we couple mass and momentum fluxes of SL9 plume material, as calculated by the ballistic Monte-Carlo plume model of Paper I of this series. A strong and complex shock structure results. The shock temperatures produced by the model agree well with observations, and the structure and evolution of the modeled shocks account for the appearance of high excitation molecular line emission after the peak of the continuum light curve. The splashback region cools by radial expansion as well as by radiation. The morphology of our synthetic continuum light curves agree with observations over a broad wavelength range (0.9-12 µm). Much of the complex structure of these light curves is a natural consequence of the temperature dependence of the Planck function, and the plume velocity distribution. A feature of our ballistic plume is a shell of mass at the highest velocities, which we term the 'vanguard'. Portions of the vanguard ejected on shallow trajectories produce a lateral shock front, whose initial expansion accounts for the 'third precursors' seen in the 2-µm light curves of the larger impacts, and for hot methane emission at early times observed by Dinelli et al. Continued propagation of this lateral shock approximately reproduces the radii, propagation speed, and centroid positions of the large rings observed at 3-4 µm by McGregor et al. The portion of the vanguard ejected closer to the vertical falls back with high zcomponent velocities just after maximum light, producing CO emission and the 'flare' seen at 0.9 µm.The model also produces secondary maxima ('bounces') whose amplitudes and periods are in agreement with observations.

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“…Heating of the interior to temperatures high enough to support liquid water will obviously not be possible so long as pressurisation is provided solely by an external layer of non-porous water ice. As a comet continues to lose ice from the surface, however, the surface will increasingly come to consist of ice-free dust particles and concentrated higher organics photopolymerised into an intractable matrix (Wilson & Sagan 1997;Matthews & Minard 2006;Simonia 2011). Silicates have a thermal conductivity that is likely to be of order 1 Wm −1 K −1 , an order of magnitude greater than the ice conductivities used in these estimates, with a heat capacity that is likely to be somewhat lower than ice (Robinson & Haas 1983).…”

Section: Subsurface Fractionationmentioning

confidence: 99%

Evolution of mobile phases in cometary interiors

Fellows

Brown

Cooper³

et al. 2020

Publ. Astron. Soc. Aust.

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Beginning with loose aggregations of dust particles coated with heterogeneous ices under vacuum at Kuiper Belt temperatures, moving to Jupiter/Saturn distances and eventually to low-perihelion orbit, we consider the likely development of the gaseous phase within a cometary nucleus over the course of its lifetime. From the perspective of physical chemistry, we consider limits on the spatial and temporal distribution and composition of this gaseous phase. The implications of the gaseous phase for heat transfer and for the possible spatial and temporal development of liquid phases are calculated. We conclude that the likely temperatures, pressures, and compositions beneath the outer crust of typical cometary nuclei are such that fluidised phases can exist at significant depths and that these reservoirs give a coherent explanation for the high-intensity outbursts observed from cometary nuclei at large distances from perihelion.

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Nature and Source of Organic Matter in the Shoemaker–Levy 9 Jovian Impact Blemishes

Cited by 4 publications

References 45 publications

The role of Fischer‐Tropsch catalysis in solar nebula chemistry

The role of Fischer‐Tropsch catalysis in solar nebula chemistry

Models of the Shoemaker‐Levy 9 Impacts. II. Radiative‐Hydrodynamic Modeling of the Plume Splashback

Evolution of mobile phases in cometary interiors

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