Morphologic Evidence for Volcanic Craters Near Titan's North Polar Region

Wood, Charles A.; Radebaugh, J.

doi:10.1029/2019je006036

Cited by 9 publications

(10 citation statements)

References 76 publications

(132 reference statements)

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“…We can imagine the formation of chemical composition gradients, driven over geological timescales by diffusion, feeding the formation of some pockets of nitrogen which could, at some point, be released abruptly bringing other materials to planetary surface. This kind of mechanism may explain morphological evidence for volcanic activity in Titan's north polar regions (Wood & Radebaugh 2020).…”

Section: Contribution Of Thermal Diffusionmentioning

confidence: 94%

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: Contribution Of Thermal Diffusionmentioning

confidence: 94%

Vertical compositional variations of liquid hydrocarbons in Titan’s alkanofers

Cordier

Bonhommeau

et al. 2021

A&A

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“…In addition, day-to-night transport from the neutral atmosphere seems to be a significant source of the night side long-lived ions [75]. Titan's thermosphere shows an unexpectedly variable N 2 (Titan's main gaseous species) density that changes by more than an order of magnitude on relatively short timescales (comparable to a few or less Titan days), accompanied by large wave-like perturbations in vertical thermal structure [253,309]. Titan, similarly to Venus, possesses an atmosphere in global superrotation, which extends up to at least 1000 km with a surprisingly high wind speed of 350 m/s [146].…”

Section: Current Knowledgementioning

confidence: 99%

“…Lakes and seas strongly differ in shape [80]. The absence of well-developed fluvial networks at the 300 m-scale of the RADAR/SAR associated with the lacustrine features, in addition to the fact that they seem to grow by coalescence in areas hydraulically and topographically disconnected from the seas, suggests that a distinct scarp retreat process is responsible for the formation and evolution of the lacustrine features on Titan ( [60,62]; Hayes et al 2016Hayes et al , 2017[260]), but do allow for a volcanic collapse or explosion origin [196,310]. Among the hypotheses elaborated on to explain the formation of the lacustrine features, the thermodynamical, geological, and chemical contexts seem to favor the formation by karstic dissolution/ evaporitic processes involving chemical dissolution/crystallization of solutes (soluble molecules) in solvents (in response to the rise or lowering of ground liquids; [55,60,62]).…”

Section: Current Knowledgementioning

confidence: 99%

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Science goals and new mission concepts for future exploration of Titan’s atmosphere, geology and habitability: titan POlar scout/orbitEr and in situ lake lander and DrONe explorer (POSEIDON)

et al. 2022

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In response to ESA’s “Voyage 2050” announcement of opportunity, we propose an ambitious L-class mission to explore one of the most exciting bodies in the Solar System, Saturn’s largest moon Titan. Titan, a “world with two oceans”, is an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. Titan is also one of the few places in the Solar System with habitability potential. Titan’s remarkable nature was only partly revealed by the Cassini-Huygens mission and still holds mysteries requiring a complete exploration using a variety of vehicles and instruments. The proposed mission concept POSEIDON (Titan POlar Scout/orbitEr and In situ lake lander DrONe explorer) would perform joint orbital and in situ investigations of Titan. It is designed to build on and exceed the scope and scientific/technological accomplishments of Cassini-Huygens, exploring Titan in ways that were not previously possible, in particular through full close-up and in situ coverage over long periods of time. In the proposed mission architecture, POSEIDON consists of two major elements: a spacecraft with a large set of instruments that would orbit Titan, preferably in a low-eccentricity polar orbit, and a suite of in situ investigation components, i.e. a lake lander, a “heavy” drone (possibly amphibious) and/or a fleet of mini-drones, dedicated to the exploration of the polar regions. The ideal arrival time at Titan would be slightly before the next northern Spring equinox (2039), as equinoxes are the most active periods to monitor still largely unknown atmospheric and surface seasonal changes. The exploration of Titan’s northern latitudes with an orbiter and in situ element(s) would be highly complementary in terms of timing (with possible mission timing overlap), locations, and science goals with the upcoming NASA New Frontiers Dragonfly mission that will provide in situ exploration of Titan’s equatorial regions, in the mid-2030s.

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“…Highly porous regolith has been previously suggested by Hayes et al (2008) for many of the polar terrains of Titan. While there have been non-karstic explanations for the formation of the Titan filled and empty lakes (such as N 2 exsolution blowout or maar formation, see: Mitri et al, 2019;Wood & Radebaugh, 2020), the full range of observed terrestrial karstic morphologies, from polygonal terrains to karstic lakes and poljes, can be adapted to Titan and explained by variations of substrate permeability.…”

Section: Network Formationmentioning

confidence: 99%

Potential Caves: Inventory of Subsurface Access Points on the Surface of Titan

et al. 2022

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The organic landscape of Saturn's moon Titan has the potential to host a plethora of solution caves and other access points into the subsurface resulting from karstic dissolution. When combined with the other speleogenic processes found on icy worlds (cryovolcanism, diapirism, and fissure formation), this makes Titan one of the best places in the solar system for planetary cave exploration. For Titan, subsurface access points, or SAPs (we use this term in lieu of "cave entrance" as the latter presupposes a cave actually exists), represent potential entrances to the subsurface that permit surface organics to be transported deeper into the interior, whether as solution or as suspended insoluble materials. For the purposes of our discussion, we are using the concept of subsurface access points (SAPs) provided by Wynne, Mylroie, et al. (2022) to imply remotely sensed features, that may or may not be connected to a subsurface void or cave, and thus potentially provide access to the subsurface of a planetary body. However, dissolution and transport of fluids to the subsurface occurs at a much smaller scale than what can be resolved via current remote sensing capabilities. Fissures, cracks, joints, and interconnected pore spaces <1 cm in size may be driving these processes at the micro-scale. These "microcaverns" (see Howarth, 1983) allow both dissolved and suspended insoluble organic materials access into the subsurface, a potential first step in delivering atmospherically-derived surface organics to warmer habitable zones in the deep ice, or possibly even into the subsurface ocean tens of kilometers below. While these features would be well below the resolution limit of current imaging of Titan's surface, we can nonetheless infer the existence of SAPs based on larger-scale phenomena associated with smaller conduit structures, such as volcanic edifices and inference of closed valleys suggesting transport of fluids and materials into the subsurface. Our work will inventory the locations where features of this size and larger could exist on Titan's surface and will detail the types of secondary mineralizations that could occur within these features.Titan is an ocean world with an icy crust covered with organic molecules. The thickness of the organic coating varies from location to location, with evidence of a 500 m thick layer in some areas, while other areas have little

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Morphologic Evidence for Volcanic Craters Near Titan's North Polar Region

Cited by 9 publications

References 76 publications

Vertical compositional variations of liquid hydrocarbons in Titan’s alkanofers

Vertical compositional variations of liquid hydrocarbons in Titan’s alkanofers

Science goals and new mission concepts for future exploration of Titan’s atmosphere, geology and habitability: titan POlar scout/orbitEr and in situ lake lander and DrONe explorer (POSEIDON)

Potential Caves: Inventory of Subsurface Access Points on the Surface of Titan

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