Titan's lakes may have been formed by underground explosions and not by erosion

In the solar system, there are only two objects with puddles of liquid supported on the surface: Earth and Titan. On Earth, we have a well-understood water cycle that keeps liquid water on the surface of our planet. On Titan, it is thought that the process is conceptually similar but that it relies on liquid methane rather than on water. There are signs that Titan has an alkanological cycle similar to the hydrological cycle of this planet. But how did Titan have his lakes remained mysterious until now. The researchers suggest that the lakes may have formed as a result of explosions and not erosion.

Most of Titan's lakes are known as "sliced ​​depressions" (SEDs). They have circular or irregular shapes that are generally not considered impact craters. On Earth, many of these types of lakes are karstic, which means that they form when a liquid (water on Earth) mine the geology located beneath an area and that it collapses, thus forming a depression that then fills up. However, there are not many substances in Titan's crust that are likely to dissolve. Organic matter that falls from Titan's atmosphere and accumulates at the poles is insufficient to create an erodible organic sedimentary layer. The researchers write:

The presence of raised ledges in the SED basins undermines the karst lake model for raised edge SEDs. According to the karstic model, lake basins on Titan should be produced as sinkholes formed by the collapse, dissolution or subsidence of the land; such processes do not produce rims. Although SEDs with raised ledges are not formed by a karstic process, their presence in a karstic environment is not excluded.

The team has another proposal on how lakes may have been formed – bombs with nitrogen. On Earth, some characteristic structures are produced by phreatic or phreatomagmatic eruptions. When seawater comes in contact with the magma, it can result in a significant steam explosion. The maars and other forms of tuff produced by this type of explosion have characteristics that correspond to the observed characteristics of the Titan lakes. We see that many Titan lakes are surrounded by ramparts made of materials, which could correspond to debris ejected from the newly formed crater as a result of a nitrogen explosion.

The theory is not perfect, because there is not as much debris around the surface of the lakes as one would expect on Earth – but that could be explained by the differences in the natural composition of Titan and its planetary evolution. One of the theories is that at a distant time, Titan's atmosphere was dominated by nitrogen, not methane, and the moon was much colder. This could have been the case if the level of methane in Titan's atmosphere was lower than it is today. As the amount of methane increased and the planet warmed up, small changes in temperature could have caused an extreme increase in pressure in the nitrogen-dominated aquifers. There may even be evidence of this kind of event occurring on Neptune's Newt during Voyager 2 flyby.

Scientists are still studying the characteristics of Titan's geology to determine if this is a plausible hypothesis, but we could learn more in the near future. NASA's Dragonfly mission to Titan is about to gather an unparalleled amount of information on this distant moon, shedding new light on its history and continued evolution.

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