No biological source for Titan Methane?

[robnissen]

http://www.space.com/scienceastronomy/ap_huygens_update_050127.html<br /><br />The credibility of this article is certainly damged by this statment, however:<br /><br />"More than a week after the Huygens probe plunged through Titan's atmosphere, researchers continue to pore over data collected for clues to how the only celestial body known to have a significant atmosphere other than Earth."<br /><br />THAT IS SURE SOME THICK VACUUM AROUND VENUS (not to mention the gas giants).<br /><br />Putting the misstatements aside, I thought this statement was very interesting:<br /><br />"Based on data collected by Huygens' instruments, Sushil Atreya, a professor of planetary science at the University of Michigan in the United States, believes a hydro-geological process between water and rocks deep inside the moon could be producing the methane. <br /><br />'I think the process is quite likely in the interior of Titan,' Atreya said in a telephone interview. <br /><br />The process is called serpentinisation and is basically the reaction between water and rocks at 100 to 400 degrees Celsius (212 to 752 degrees Fahrenheit), he said."<br /><br />I wonder what evidence there is for that much of a heat source on Titan. And, with that kind of heat and liquid water, it sure would be interesting looking for microbes in Titan's interior.<br /><br />

 

[rogers_buck]

Deleted, because I don't want to take this thread on a tangent...

 

[rogers_buck]

Humm, inside Titan there is liquid water because of geothermic and tidal heating. Presumably there is plenty of things for bugs to eat. If methane was vented as a result of hydro chemical reactions with the rocks, then the organic rain on Titan's surface has been going on for a long time. If there is a transport of the large polymers on the surface to the interior, like subduction on the earth, then you would have complex organics, liquid water, and plenty to eat inside Titan. If that resulted in more complex chemistry, aka life, then you would have even more methane production from the potential bugs.<br /><br />On earth mothane gets trapped in methane ices at high pressure and low temperatures on the sea bed. On Titan it is vented and gets processed through the atmosphere and returned to the surface as complex organics. Almost a mirror image, no?<br />

 

[rogers_buck]

Sorry steve, it isn't as simple as you presume. Titan's thick methane atmosphere is verry much a topic of conjecture and is not explained by fossil methane from accretion. Read the cover story on SDC:<br /><br />http://www.space.com/scienceastronomy/ap_huygens_update_050127.html<br /><br />And you can get a better position on methane without life.

 

[earthseed]

The equilibrium in Titan's atmosphere must include a planetary source of methane, as it is destroyed by ultra-violet light. Any process that can produce a steady flow of methane for four billion years is rather interesting. The one suggested in the article involves geothermal heat sources, which has huge implications.<br /><br />I did not see a reason given why the methane source is not biological. Unfortunalely, Huygens could not measure the ¹³C/¹²C isotope ratios, which on Earth are used to determine if carbon has a biogenic origin.

 

[munkin]

I think that the isotope ratio of methane can be measured from the probe's instruments. From what I understand the ESA scientists have not figured out the ratio yet. If the CH4 isotope is predominantly 12 rather than 13 - it will be interesting how this isotope can be explained geologically. CH4 isotope 12 is produced biologically on Earth.<br /><br />If CH4 isotope 13 is found to be the predominant isotope - than the methane should be produced from within Titan geologically rather than from a biologic source.

 

[munkin]

Can you cite scientific journal sources to back up this statement:<br /><br />"Titan's atmosphere is in a thermodynamic, chemical equilibrium".<br /><br />Thanks!

 

[robnissen]

"Titan is simply too cold for any kind of living biochemical processes." <br /><br />Titan is NOT too cold, if as the article states, there are internal heat sources on Titan between "100 to 400 degrees Celsius (212 to 752 degrees Fahrenheit)." <br /><br />Now I don't believe we yet know whether Titan contains that kind of heat source, but, at the very least, such a heat source can not yet be ruled out.<br /><br />

 

[earthseed]

I found this interesting paper on The origin and nature of Titan's methane. They clam that "Titan is roughly 52% rock and 48% ice", the ice being a mixture of water, ammonia and methane. This makes for a huge "methanifer" (rather than aquifer) that continually supplies the atmosphere with methane. There is no mention of a high temperature reaction between water and rocks to produce methane, as stated in the origina article referenced in this thread.<br /><br />Here is the proposed internal structure of Titan. Note the presence of a layer of liquid ammonia-water ocean. So there is no need for biology to provide methane, it seems Titan's structure does not rule it out.

 

[earthseed]

Any description of the interior of Titan is going to be a bit hypothetical, given that we are still unsure about the interior of the Earth. I felt the article was a reasonable summary of current thinking on the subject.<br /><br />Hopefully, with the new information from Cassini and Huygens, this picture can be updated.