Titan: Case of the Missing Methane (and Ethane)
In Astrobiology Magazine this week, an article explained why the lack of methane and ethane oceans on Titan is so mysterious. Jonathan Lunine, a chemist and astrobiologist who has been studying Titan for over two decades, explained why these hydrocarbons ought to be there. Methane (CH4) is split by ultraviolet light from the sun. The hydrogen drifts off to space, leaving more carbons and fewer hydrogen atoms. These join into more complex hydrocarbons, especially ethane (C2H6) which precipitate out of the clouds and fall to the ground. Ethane and methane should both be liquid at the 95K temperatures on the surface.
Since this chemistry is irreversible, we can say that products are being made and deposited on the surface. If the chemistry on Titan has gone on in steady-state over the age of the solar system, then we would predict that a layer of ethane 300 to 600 meters thick should be deposited on the surface. That would make it the biggest hydrocarbon reservoir on any of the solid bodies in the solar system. (Emphasis added in all quotes.)
Yet even before Huygens landed (see 01/21/2005 story), it was clear the ethane was not there, and none of the expected oceans of methane were detectable. The only alternative explanations Lunine can think of are (1) there are unknown reservoirs of methane under the surface, or (2) “the chemistry is an occasional process, and we happen to be seeing Titan today at a time when chemistry is ongoing, where there is enough methane in the atmosphere.” (Generally, planetary scientists try to avoid the notion that humans are living in a special time when unusual things are happening.) (3) A third idea is that some less-dense hydrocarbon, like polyacetylene, is floating on the oceans and covering them up.
Sorry, astrobiologists, you lost the prediction (see 01/15/2005 commentary). You cannot keep multiplying ad hoc assumptions to keep your falsified tale alive.
Notice that Lunine did not even consider the possibility that Titan is young. The belief that these objects are billions of years old is sacrosanct, because the Darwin Party thought police will not tolerate thefts of the time they need to evolve molecules into men.