Ammonium sulfate on Titan: Possible origin and role in cryovolcanism

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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“…The sources of these methane extrusions in both moons have been related to clathrate hydrate dissociation (5,38,39).…”

Section: Discussionmentioning

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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“…These include hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides (Bryson and Goodman, 1980). Fortes et al (2007) suggest methane gas, carbon monoxide and nitrogen as possible volatile volcanic gases candidates in Titan's magma. In this study, employing a model that we named the 'CO 2 model', we suggest one more candidate -carbon dioxide.…”

Section: Modellingmentioning

confidence: 99%

Modelling of Volcanic Eruptions on Titan

Solomonidou¹,

Fortes²,

Kyriakopoulos³

2017

geosociety

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Observations by the Visual Infrared Spectrometer instrument (VIMS) aboard the Cassini mission haveindicated the possible presence of CO2 ice on the surface on Titan, in areas which exhibit highreflectance in specific spectral windows (McCord et al., 2008). Two of the bright spots of significanceare located within the Xanadu region – Tui Regio (located at 20°S, 130°W) and Hotei Regio (locatedat 26°S, 78°W), and there is a further spot situated in proximity to Omacatl Macula (Hayne et al.,2008). Explosive volcanic eruptions of a cryomagma containing H2O and CO2 are modelled forseveral potential scenarios regarding entrained CO2 clathrates. The model yielded a range of valuescorresponding to the fragmentation pressure in the lava conduit, the velocity of the explodingcryomagma, the height of the associated lava fountain and the potential distance covered by ejecta.The results show that a single vent source does not possess the force required to cover an arearesembling Hotei Regio or Tui Regio. Therefore, we consider alternative origins: the area may havebeen resurfaced by small CO2 grains resulting from multiple explosive eruptions emanating from azone of weakness (Hayne et al., 2008); the characteristics of the area are consequential of an eruptionof cryomagma with CO2 and NH3 components (McCord et al., 2008); or finally, long term seasonalwinds transferred small CO2 grains and distributed them within the limits of Tui Regio area.

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“…Possible venting mechanisms are sudden decompression of near-surface reservoirs of liquid water [33], clathrate decomposition [20], or other cryovolcanic processes [12].…”

Section: Interior and Early Evolutionmentioning

confidence: 99%

“…These data as well as remote sensing visual, infrared and radar data, will be used to assess the depth and composition of the cryomagmatic reservoir. In the case of Titan, ammonia, methane and carbon dioxide mixing ratios will help distinguish between different hypotheses about replenishing volatiles in its atmosphere [5,12,47]. Subsurface sounding and gravity measurements will also be used to identify cryomagmatic chambers below cryovolcanic edifices.…”

Section: Interior and Early Evolutionmentioning

confidence: 99%

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TandEM: Titan and Enceladus mission

et al. 2008

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International audienceTandEM was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (Montgolfière) and possibly several landing probes to be delivered through the atmospher

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Ammonium sulfate on Titan: Possible origin and role in cryovolcanism

Cited by 157 publications

References 111 publications

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

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

Modelling of Volcanic Eruptions on Titan

TandEM: Titan and Enceladus mission

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