Mystery about the veil of Titan
How long can the Saturn moon keep its atmosphere?Read out
How long can the Titan keep its dense, organic atmosphere? Since Huygens' probe on Saturn's moon, it has become clear that methane is one of the driving forces behind the atmosphere. But the hydrocarbon gas has to be constantly renewed. How, planet scientists have been arguing about this for quite some time.
Saturn's moon Titan has long been regarded as a promising candidate for extraterrestrial life in our solar system. One of the reasons for this is its dense atmosphere of nitrogen, methane and various organic compounds. Due to the interaction of these compounds with the sunlight, the lunar surface is permanently covered by a dense smog shell. For example, before landing the ESA probe Huygens, it was completely unclear what was on the surface: methane ice? Lakes of hydrocarbons? Maybe even water? Meanwhile, the results of the Cassini-Huygens mission have revealed that there are likely lakes of hydrocarbons on the Titan.
"When titanium emits methane and loses its 'veil', it becomes a completely different kind of celestial body, " explains Vasili Dimitrov of the University of Tel-Aviv at the European Congress of Planetary Sciences in Potsdam. "Methane fuels chemical reactions in the atmosphere, but because it is so highly reactive and therefore short-lived, it needs to be constantly renewed. We therefore need to find out how much methane is stored in the primeval reserves inside the Moon so that it can escape over time. "
Permafrost on ice
Below the surface of Titan is a permafrost layer that sits on a liquid or semi-liquid layer of ammonia, methane and water. Underneath, a layer of ice surrounds the rocky core of the moon. Exactly this layer of ice is currently the focus of interest. Because it probably contains the methane reserves of the moon. Researchers now need to learn how the methane molecules in these reservoirs have been "packaged" to deduce their release and availability to the atmosphere. display
In the ice layer, the methane is embedded in special molecular assemblies called clathrates. In these compounds, water molecules combine to form cubic crystals, which form a kind of cage around the methane. This type of packaging is most effective when it occurs at temperatures near absolute zero. If it is warmer, an increasing number of cages will remain empty. In order to know how much methane is stored inside the Titan, the researchers have to find out how high the proportion of empty cages is.
"The conditions during the formation and development of titanium are poorly understood so far, " says Dimitrov. "So we can not say yet how many of the cages are filled and how much methane is in the reservoirs. While we can set upper and lower bounds on packing density at the moment, that does not tell us when the titanium methane stocks will start falling. "
Goodbye to a veil?
It is also unclear whether the methane trapped in this ice layer has any chance of reaching the surface. "We also have to do some laboratory experiments to find out more about the material transport between the different layers, " says Dimitrov. "With further experiments, along with the data provided by the Cassini-Huygens mission, we should soon be able to answer if and for how long this fascinating world retains its mysterious veil."
However, research on clathrates is not only exciting for planetary scientists, but also on Earth, these raw material cages are becoming more and more important. After all, the terrestrial methane stock stored in such compounds could be four times more extensive than the entire remaining oil. According to the researchers, methane could someday even become one of the main sources of human energy.
(Royal Astronomical Society (RAS), 21.08.2007 - NPO)