Titan’s missing ethane: From the atmosphere to the subsurface

Gilliam, Ashley E.; Lerman, Abraham

doi:10.1016/j.icarus.2016.04.025

Cited by 6 publications

(5 citation statements)

References 55 publications

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“…First of all, the methane potentially stored in these reservoirs may participate significantly in the global carbon cycle of Titan (Horvath et al 2016;Faulk et al 2020). Secondly, the lack of ethane on the surface of Titan is a long-standing problem (Mousis et al 2016;Gilliam & Lerman 2016); a response to this question could consist of a chemical vertical stratification of subsurface liquids. Since ethane (molecular weight: 30 g mol −1 ) is heavier than nitrogen (28 g mol −1 ) and methane (16 g mol −1 ), ethane-enriched layers could exist in Titan's deep alkanofers.…”

Section: Introductionmentioning

confidence: 99%

Vertical compositional variations of liquid hydrocarbons in Titan’s alkanofers

Cordier

Bonhommeau

et al. 2021

A&A

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Context. According to clues left by the Cassini mission, Titan, one of the two Solar System bodies with a hydrologic cycle, may harbor liquid hydrocarbon-based analogs of our terrestrial aquifers, referred to as “alkanofers”. Aims. On the Earth, petroleum and natural gas reservoirs show a vertical gradient in chemical composition, established over geological timescales. In this work, we aim to investigate the conditions under which Titan’s processes could lead to similar situations. Methods. We built numerical models including barodiffusion and thermodiffusion (Soret’s effect) in N2+CH4+C2H6 liquid mixtures, which are relevant for Titan’s possible alkanofers. Our main assumption is the existence of reservoirs of liquids trapped in a porous matrix with low permeability. Results. Due to the small size of the molecule, nitrogen seems to be more sensitive to gravity than ethane, even if the latter has a slightly larger mass. This behavior, noticed for an isothermal crust, is reinforced by the presence of a geothermal gradient. Vertical composition gradients, formed over timescales of between a fraction of a mega-year to several tens of mega-years, are not influenced by molecular diffusion coefficients. We find that ethane does not accumulate at the bottom of the alkanofers under diffusion, leaving the question of why ethane is not observed on Titan’s surface unresolved. If the alkanofer liquid was in contact with water-ice, we checked that N2 did not, in general, impede the clathration of C2H6, except in some layers. Interestingly, we found that noble gases could easily accumulate at the bottom of an alkanofer.

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Section: Introductionmentioning

confidence: 99%

Vertical compositional variations of liquid hydrocarbons in Titan’s alkanofers

Cordier

Bonhommeau

et al. 2021

A&A

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“…26 Lightning, whcih is well-known in Earth's atmosphere, was confirmed in more planetary atmospheres. 21,27,28,35 While the occurrence of lightning on Venus is still a controversial question, 36,37 there is clear evidence of lightning in the atmospheres of the gas giants like Jupiter, Saturn, 38 and Uranus. 39−41 Lightning is also believed to take place at Neptune.…”

Section: Introductionmentioning

confidence: 99%

“…This means that even if no discharge is presented as it is known, the ions would be existing anyway. 29,33,35 The planetary scale chemical processes initiated by electrical discharge can be simulated by laboratory experiments using various discharges: corona and DBD conditions are similar to the St. Elmo's fire, spark and arc discharges are related to the lightning, and corona and glow discharge conditions are similar to the conditions in the aurora borealis. 28,34 Up to now, nearly all laboratory studies of Titan's atmosphere and the discharge initiated processes have been carried out at ambient temperature and pressure that were not fully reflecting Titan's real surface conditions.…”

Section: Introductionmentioning

confidence: 99%

“…It is assumed that the electrical discharge phenomena can play an important role in the atmospheric chemistry at lower altitudes . Lightning, whcih is well-known in Earth’s atmosphere, was confirmed in more planetary atmospheres. ,,, While the occurrence of lightning on Venus is still a controversial question, , there is clear evidence of lightning in the atmospheres of the gas giants like Jupiter, Saturn, and Uranus. − Lightning is also believed to take place at Neptune. , Moreover, it was pointed out very recently that the lightning activity in Jupiter’s atmosphere is significantly higher than was expected, and thus the same situation can be also assumed in other atmospheres . Besides the classical lightning phenomena, transient lightning events like sprites, jets, and elves were recently also confirmed in the atmospheres of Venus, Mars, and Jupiter …”

Section: Introductionmentioning

confidence: 99%

“…In general, the important role of ionic chemistry is known and broadly studied. , In addition to the ions generated by the discharge, of course, the ions formed by the radiation from the Universe, mainly at the upper atmosphere, are important or even dominant. This means that even if no discharge is presented as it is known, the ions would be existing anyway. ,, …”

Section: Introductionmentioning

confidence: 99%

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Study of Chemical Processes Initiated by Electrical Discharge in Titan-Related Atmosphere at Laboratory Temperature and Pressure

Chudják

Kozáková

Krčma

2021

ACS Earth Space Chem.

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The chemical processes initiated by electrical discharges in prebiotic atmospheres became a hot topic during the past decade due to the recent extensive discovery of exoplanets. The biggest atmospheric data collection is currently available about the atmosphere of the Saturn's moon Titan that is composed mainly of nitrogen and methane at low surface temperature of about 95 K and pressure of about 1.5 atm. The present work deals with the laboratory simulation of the chemical processes initiated by the electrical discharge in the gaseous mixture related to the Titan atmosphere under laboratory conditions. The ongoing chemical processes, the resulting stable products, and their transformation into more complex substances were studied by the in situ mass spectrometry with proton ionization (PTR-MS) of the exhausting gas. The presence of many aliphatic and some aromatic hydrocarbons was confirmed as well as many amino and cyano compounds. The increasing concentration of methane has produced more substances with higher molecular weight and less simple substances that were consumed in the formation of more complex substances.

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