High-temperature shock formation of N2 and organics on primordial Titan

McKay, Christopher P.; Scattergood, T. W.; Pollack, James B.; Borucki, W. J.; Ghyseghem, H. T. van

doi:10.1038/332520a0

Cited by 90 publications

(63 citation statements)

References 16 publications

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“…A primordial atmosphere of ammonia, or molecular nitrogen with some methane, undergoes rapid escape and enrichment of the heavier isotopes. If the nitrogen is in the form of ammonia, photochemical or impact-generated chemistry converts that molecule to molecular nitrogen (Atreya et al, 1978;McKay et al, 1988;Jones and Lewis, 1987;Atreya et al, 1978). As the atmosphere and surface cool down, the residual ammonia (much less volatile than the nitrogen) condenses on the surface leaving the molecular nitrogen behind in the gas phase.…”

Section: Titan's Early History Based On the Enrichments Of 15 N And Cmentioning

confidence: 99%

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

Lunine

Yung

Lorenz

1999

Planetary and Space Science

102

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We analyze recently published nitrogen and hydrogen isotopic data to constrain the initial volatile abundances on Saturn's giant moon Titan. The nitrogen data are interpreted in terms of a model of non-thermal escape processes that lead to enhancement in the heavier isotope. We show that these data do not, in fact, strongly constrain the abundance of nitrogen present in Titan's early atmosphere, and that a wide range of initial atmospheric masses (all larger than the present value) can yield the measured enhancement. The enrichment in deuterated methane is now much better determined than it was when Pinto et al. (1986. Nature 319, 388±390) ®rst proposed a photochemical mechanism to preferentially retain the deuterium. We develop a simple linear theory to provide a more reliable estimate of the relative dissociation rates of normal and deuterated methane. We utilize the improved data and models to compute initial methane reservoirs consistent with the observed enhancement. The result of this analysis agrees with an independent estimate for the initial methane abundance based solely on the present-day rate of photolysis and an assumption of steady state. This consistency in reservoir size is necessary but not su cient to infer that methane photolysis has proceeded steadily over the age of the solar system to produce large quantities of less volatile organics. Our analysis indicates an epoch of early atmospheric escape of nitrogen, followed by a later addition of methane by outgassing from the interior. The results also suggest that Titan's volatile inventory came in part or largely from a circum-Saturnian disk of material more reducing than the surrounding solar nebula. Many of the ambiguities inherent in the present analysis can be resolved through Cassini±Huygens data and a program of laboratory studies on isotopic and molecular exchange processes. The value of, and interest in, the Cassini±Huygens data can be greatly enhanced if such a program were undertaken prior to the prime phase of the mission. #

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Section: Titan's Early History Based On the Enrichments Of 15 N And Cmentioning

confidence: 99%

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

Lunine

Yung

Lorenz

1999

Planetary and Space Science

102

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“…Atmospheric deceleration of the downrange-moving vapor clouds controls the downrange offset of the source regions of run-out flows, and condensation from this cloud may comprise much of the run-out material [Schultz, 1992;Sugita and Schultz, 2002]. Second, shock interaction between impact vapor clouds and atmosphere may produce a large amount of thermodynamically metastable chemical compounds, such as simple organic molecules in the early Earth atmosphere [e.g., Fegley et al, 1986;McKay and Borucki, 1997], nitrogen oxides in the modern atmosphere [e.g., Zahnle, 1990], and N 2 in the Titan atmosphere [McKay et al, 1988]. Third, the expansion of high-energy impact vapor clouds on planets and satellites during the latestage heavy bombardment period has been proposed to JOURNAL OF GEOPHYSICAL RESEARCH, VOL.…”

Section: Introductionmentioning

confidence: 99%

Interactions between impact‐induced vapor clouds and the ambient atmosphere: 1. Spectroscopic observations using diatomic molecular emission

Sugita

Schultz

2003

J. Geophys. Res.

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[1] The importance of interactions between impact-induced vapor clouds and an ambient atmosphere has been widely recognized, and theoretical approaches have provided significant insights. Few experiments, however, have been done to observe directly the energy partitioning during the interactions between impact vapor clouds and the ambient atmosphere. The present study attempts to understand the difference between actual and theoretical model impact vapor clouds produced under an atmosphere. A series of hypervelocity impact experiments was conducted using a spectroscopic measurement method. Plastic (polycarbonate) impactors allowed simulating vaporization phenomena associated with natural impactors (e.g., silicates and metals) at high impact velocities into water. Water as the target material served to suppress the effect of fine-grained fragments from the target. Emission spectra of the leading part of downrange-moving impact vapor clouds were captured with high-speed spectrometers as a function of time for various ambient pressures. The emission spectra exhibit strong molecular bands from carbon compounds as well as blackbody continuum radiation. In order to estimate the temperature of the radiation source, we carried out a spectral-form inversion analysis based on diatomic emission theory. Obtained molecular radiation temperatures range from 4500 K to 5500 K with relatively high accuracy ($2%) and place a number of well-defined constraints for the radiation source. A simple theoretical model that is often assumed for an impact-induced vapor cloud, however, does not readily satisfy the constraints. This strongly suggests that real impact-induced vapor clouds may be more complex than previously thought.INDEX TERMS: 5420 Planetology: Solid Surface Planets: Impact phenomena (includes cratering); 5407 Planetology: Solid Surface Planets: Atmospheres-evolution; 5455 Planetology: Solid Surface Planets: Origin and evolution; 5494 Planetology: Solid Surface Planets: Instruments and techniques; 6022 Planetology: Comets and Small Bodies: Impact phenomena; KEYWORDS: Impact cratering, impact experiments, impact vaporization, impact flash spectroscopy, molecular emission Citation: Sugita, S., and P. H. Schultz, Interactions between impact-induced vapor clouds and the ambient atmosphere: 1.

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“…The ratio of CO to CH 4 in Titan's atmosphere (Gautier and Raulin 1997) is orders of magnitude lower than the ratio determined for the PSN (Lodders 2003), suggesting either that Titan's building blocks were initially enriched in CH 4 (Lunine 1989) or that the building blocks were rich in CO that was later converted to CH 4 through aqueous processes in the interior (Atreya et al 2006). The nitrogen could have originated as N 2 or as NH 3 that was later converted to N 2 by photochemical processing in the early atmosphere (Atreya et al 1978), impact shock heating (McKay et al 1988), or endogenic processes (Glein et al 2008).…”

Section: Titanmentioning

confidence: 95%

Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites

et al. 2015

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Comets play a dual role in understanding the formation and evolution of the solar system. First, the composition of comets provides information about the origin of the giant planets and their moons because comets formed early and their composition is not expected to have evolved significantly since formation. They, therefore serve as a record of conditions during the early stages of solar system formation. Once comets had formed, their orbits were perturbed allowing them to travel into the inner solar system and impact the planets. In this way they contributed to the volatile inventory of planetary atmospheres. We review here how knowledge of comet composition up to the time of the Rosetta mission has contributed to understanding the formation processes of the giant planets, their moons and small icy bodies in the solar system. We also discuss how comets contributed to the volatile inventories of the giant and terrestrial planets.

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High-temperature shock formation of N2 and organics on primordial Titan

Cited by 90 publications

References 16 publications

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

Interactions between impact‐induced vapor clouds and the ambient atmosphere: 1. Spectroscopic observations using diatomic molecular emission

Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites

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