In the Solar System, only two stars have liquid environments on their surfaces. The Earth, of course, but also TitanTitanfrozen moon SaturnSaturn. The resemblance between these two bodies, however, ends there, or almost. Because, if on Earth, it is indeed liquid water that flows, on Titan, there are rivers and lakes of methane and other hydrocarbons which adorn an icy and desert landscape where a temperature of -180°C reigns.
These lakes, where it would not be good to swim, are particularly located in the polar regions. By studying them, scientists noticed that some were nestled in small craters of around ten kilometers in diameter which are characterized by raised edges, hence their name “rampart craters”.
This morphologymorphology crater is well known on Mars in particular, where they were produced by meteorite impacts. However, scientists believe that their origin is completely different on Titan, and that it would be much more similar to certain craters observed on Earth.
Very similar craters on Earth
For around ten years, we have indeed been witnessing the formation of strange craters in the frozen plains of Siberia. If, at the beginning, the sudden formation of these gaping holes in the permafrostpermafrost asked the researchers, recent studies have revealed their origin. These would in fact be craters formed not by the fall of a meteoritemeteoritebut by an explosion of natural gas contained in the subsoil and in particular in the methane hydrate ices located at depth. THE global warmingglobal warmingby affecting the surface zone of the permafrost, would induce a destabilization of these deep frozen levels, leading to the release of methane. The increase in pressionpression within the rocks would eventually produce a violent explosion, forming a hole very similar to the rampart craters observed on the surface of Titan.
However, we know that the basement of Titan must have a significant layer of methane hydrates. Is it possible that the craters on this moon are formed following the same mechanism as on Earth?
Different possible scenarios
For researchers behind an article published in the journal Journal of Geophysical Research : Planetthis is a possibility that should not be overlooked. Until now, the rampart craters of Titan were associated either with the formation of “karst” by dissolution of a crustcrust of hydrocarbon ice by liquid hydrocarbons, or of volcanic origin, particularly during maar-type explosions which occur when water, infiltrating into the crust, encounters a reservoir of magmamagma. On Titan, the reagentsreagents would not, however, be completely the same, the magma being replaced by cryomagma aqueousaqueousand water by liquid hydrocarbons. However, these hypotheses did not completely satisfy the observations.
GE Brouwer and his colleagues at the University of Hawaii therefore carried out a series of modelingmodeling to test the two most probable hypotheses: explosions of the type butbut or an explosion by methane accumulation following destabilization of methane hydrates.
Their results reveal that depending on the composition of Titan’s crust, both of these hypotheses may be valid. The maar type explosion would be favored in the case of a crust composed solely of water ice, while the explosion by emissionemission of methane would be more plausible in the context of a crust mainly formed of organic compounds. In both scenarios, however, the quantity of methane emitted during the explosion would be sufficiently large, 1011 at 1014 kgkgto ensure the maintenance of a atmosphereatmosphere rich in methane, a particularity of Titan whose origin was until now poorly understood.
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