Several years ago, astronomers discovered strangely shaped lakes on Saturn's moon Titan. Now scientists have put forward an intriguing version of their origin: "reservoirs" could be formed as a result of powerful explosions.
Details are described in a scientific article published in the journal Nature Geoscience.
Let us recall that Titan is the only body in the solar system, except for the Earth, on the surface of which liquid exists stably. But this is not water. It is so cold on a celestial body that the seas and lakes of the satellite are filled with liquid methane and ethane.
How were these lakes formed? Most experts believe that karst processes (dissolution of rocks in a liquid) are to blame. This is how many bodies of water appeared on Earth.
However, a few years ago, researchers discovered lakes with raised edges on Titan. Round “methane ponds” tens of kilometers in diameter are surrounded by ramparts tens and hundreds of meters high. An example is Lake Winnipeg Lacus. The ring around it reaches a height of 300 meters, while the depth of the lake itself is only about 100 meters.
This geometry cannot be explained by karst phenomena. When some of the soil dissolves into a liquid, a depression is formed, but not a hill.
In the new study, astronomers used radar data obtained during the last rendezvous of the Cassini spacecraft with Titan. This allowed scientists to study in more detail the shape of the anomalous lakes and finally make sure that the karst model does not work in this case.
But what could explode with such force on the moon of Saturn? Astronomers have a version that we are talking about the so-called steam explosions.
This phenomenon occurs when a large amount of liquid (or solid) instantly turns into steam. This hot gas creates tremendous pressure, capable of literally tearing apart any cavity from the inside in which the vaporized substance was enclosed.
On Earth, this happens when groundwater suddenly comes into contact with hot magma. And by the way, craters are formed that are extremely similar to the unusual lakes of Titan.
What could turn into steam on the moon of Saturn, cold as the heart of the former? The authors believe that it is nitrogen.
In fact, Titan is not at all as cold as it could be. Methane in its atmosphere acts as a greenhouse gas, blocking infrared radiation from the surface and preventing it from carrying heat into space.
However, scientists believe there have been periods in Titan's past when it was poor in methane gas. This substance is released into the atmosphere from the surface and is simultaneously destroyed by sunlight. These two processes cause the methane content in the satellite's gas envelope to fluctuate.
When there is little methane in the atmosphere, it gets really cold. The atmosphere is almost entirely nitrogen. Partly it turns into a liquid, accumulating in the ground. But in the event of warming, such "deposits" can quickly turn back into gas, setting up a steam explosion. According to the team's calculations, enough energy is released in this case to form a suitable funnel.