Titan Tholins: Simulating Titan Organic Chemistry in the Cassini-Huygens Era

Cable, Morgan L.; Hörst, Sarah M.; Hodyss, Robert; Beauchamp, P.; Smith, Mark A.; Willis, Peter

doi:10.1021/cr200221x

Cited by 214 publications

(222 citation statements)

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“…One of the difficulties encountered when simulating the synthesis of organic aerosols is to prevent samples from air contamination when collecting them and bringing them to external analytical devices (Cable et al 2012). Without any specific precaution the analogues adsorb and react on their surface with oxygen, leading to a few percent of oxygen in their elemental composition .…”

Section: Simulation Facilities For Organic Aerosols In Planetary Atmomentioning

confidence: 99%

Earth as a Tool for Astrobiology—A European Perspective

et al. 2017

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Scientists use the Earth as a tool for astrobiology by analyzing planetary field analogues (i.e. terrestrial samples and field sites that resemble planetary bodies in our Solar System). In addition, they expose the selected planetary field analogues in simulation chambers to conditions that mimic the ones of planets, moons and Low Earth Orbit (LEO) space conditions, as well as the chemistry occurring in interstellar and cometary ices. This paper reviews the ways the Earth is used by astrobiologists: (i) by conducting planetary field analogue studies to investigate extant life from extreme environments, its metabolisms, adaptation strategies and modern biosignatures; (ii) by conducting planetary field analogue studies to investigate extinct life from the oldest rocks on our planet and its biosignatures; (iii) by exposing terrestrial samples to simulated space or planetary environments and producing a sample analogue to investigate changes in minerals, biosignatures and microorganisms. The European Space Agency (ESA) created a topical team in 2011 to investigate recent activities using the Earth as a tool for astrobiology and to formulate recommendations and scientific needs to improve ground-based astrobiological research. Space is an important tool for astrobiology (see Horneck et al. in Astrobiology, 16:201-243, 2016;Cottin et al., 2017), but access to space is limited. Complementing research on Earth provides fast access, more replications and higher sample throughput. The major conclusions of the topical team and suggestions for the future include more scientifically qualified calls for field campaigns with planetary analogy, and a centralized point of contact at ESA or the EU for the organization of a survey of such expeditions. An improvement of the coordinated logistics, infrastructures and funding system supporting the combination of field work with planetary simulation investigations, as well as an optimization of the scientific return and data processing, data storage and data distribution is also needed. Finally, a coordinated EU or ESA education and outreach program would improve the participation of the public in the astrobiological activities.

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Section: Simulation Facilities For Organic Aerosols In Planetary Atmomentioning

confidence: 99%

Earth as a Tool for Astrobiology—A European Perspective

et al. 2017

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“…Later, Vinogradoff et al (2012) confirmed the importance of methanimine in the formation of 1,3,5-triazinane (an intermediate species toward hexahydro-1,3,5-triazine formation) and polymethylenimine in non-UV exposed NH 2 CH 2 OH:HCOOH ice mixtures between 290 and 330 K. Vuitton et al (2007) suggested that a similar process could account for the missing quantitative loss process in the atmosphere of Titan, while Lavvas et al (2008a,b) went further by suggesting that polymerization of methanimine could be an important step in the formation of the haze aerosols in the Titan upper atmosphere. Indeed, there is overwhelming evidence that the aerosols, which form the haze of Titan, are composed of organic macromolecules that are very rich in nitrogen (Israel et al 2015;Imanaka & Smith 2010;Gu et al 2009;Carrasco et al 2009;Cable et al 2012). Therefore, CH 2 =NH is an excellent monomer candidate to account for the nitrogen-rich aerosols of Titan through polymerization.…”

Section: Introductionmentioning

confidence: 99%

Dimerization of methanimine and its charged species in the atmosphere of Titan and interstellar/cometary ice analogs

Skouteris

Balucani

Falcinelli

et al. 2015

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Aims. We theoretically investigated the dimerization of methanimine, CH 2 =NH, a process that has been invoked to explain the formation of haze in the atmosphere of Titan and nitrogen organic compounds in interstellar/cometary ice analogs. Methods. We used density functional theory to characterize the minima and transition states of the investigated processes, while we computed the energetics with the more accurate coupled cluster method. We then obtained rate coefficients via combination of capture theory and statistical calculations. Results. The process involving two neutral molecules is characterized by significant energy barriers and cannot occur under the low temperature conditions of Titan or interstellar/cometary ices unless an external energy source is provided. On the contrary, the processes involving one molecule of either ionized or protonated methanimine are barrierless reactions and can therefore contribute to the formation of larger ions. In particular, the reaction involving ionized methanimine can also be efficient in the very low temperature conditions of the interstellar medium, leading to products of general formula C 2 N 2 H + .Conclusions. The present work suggests that polymerization of methanimine is not an efficient process in space unless an ionization/protonation or a significant energy source is available.

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“…ice | single crystal X-ray diffraction | hydrogen bonding | hydrate inhibitors | ethane A mmonia has long been seen as a key species in extraterrestrial space, both interstellar and on outer planets, moons, and comets and the interplay of ammonia, methane, and water has been the subject of a considerable number of studies and speculation (1)(2)(3)(4)(5)(6)(7)(8). The main role assigned to ammonia has been that of an antifreeze for ice and clathrate hydrate formation, modifying the stability region of the solid ice and methane clathrate hydrate phases as a thermodynamic inhibitor (2,5,9).…”

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confidence: 99%

Ammonia clathrate hydrates as new solid phases for Titan, Enceladus, and other planetary systems

Shin

Kumar

Udachin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

129

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There is interest in the role of ammonia on Saturn's moons Titan and Enceladus as the presence of water, methane, and ammonia under temperature and pressure conditions of the surface and interior make these moons rich environments for the study of phases formed by these materials. Ammonia is known to form solid hemi-, mono-, and dihydrate crystal phases under conditions consistent with the surface of Titan and Enceladus, but has also been assigned a role as water-ice antifreeze and methane hydrate inhibitor which is thought to contribute to the outgassing of methane clathrate hydrates into these moons' atmospheres. Here we show, through direct synthesis from solution and vapor deposition experiments under conditions consistent with extraterrestrial planetary atmospheres, that ammonia forms clathrate hydrates and participates synergistically in clathrate hydrate formation in the presence of methane gas at low temperatures. The binary structure II tetrahydrofuran + ammonia, structure I ammonia, and binary structure I ammonia + methane clathrate hydrate phases synthesized have been characterized by X-ray diffraction, molecular dynamics simulation, and Raman spectroscopy methods.ice | single crystal X-ray diffraction | hydrogen bonding | hydrate inhibitors | ethane A mmonia has long been seen as a key species in extraterrestrial space, both interstellar and on outer planets, moons, and comets and the interplay of ammonia, methane, and water has been the subject of a considerable number of studies and speculation (1-8). The main role assigned to ammonia has been that of an antifreeze for ice and clathrate hydrate formation, modifying the stability region of the solid ice and methane clathrate hydrate phases as a thermodynamic inhibitor (2, 5, 9). However, ammonia is a methane-sized molecule, thus based on size alone it has the potential for being a suitable guest for clathrate hydrate cages. Issues that may have prevented ammonia from being considered as a suitable clathrate guest molecule include the notion that guest species need to be hydrophobic in order to be incorporated into clathrates, and the observation of a number of stoichiometric nonclathrate phases of ammonia and water obtained upon cooling aqueous ammonia solutions (2). Previous experimental work on the water-ammonia and water-methaneammonia systems had not shown evidence for the enclathration of ammonia (5,(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Close inspection, however, shows that the low pressure ammonia dihydrate (18) and the high pressure phase II of ammonia monohydrate (19) have structural features in common with canonical clathrate and semiclathrate structures.Recent structural analysis and molecular simulations have shown that some guest molecules which form strong hydrogen bonds with the water framework of the clathrate hydrate lattice may nonetheless produce stable phases (20-23). It is therefore reasonable to consider that ammonia has potential as a clathrate guest molecule. Furthermore, previous experimental and computational studies hav...

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Titan Tholins: Simulating Titan Organic Chemistry in the Cassini-Huygens Era

Cited by 214 publications

References 214 publications

Earth as a Tool for Astrobiology—A European Perspective

Earth as a Tool for Astrobiology—A European Perspective

Dimerization of methanimine and its charged species in the atmosphere of Titan and interstellar/cometary ice analogs

Ammonia clathrate hydrates as new solid phases for Titan, Enceladus, and other planetary systems

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