One more reason to lament having given up hard SF... thanks for the post, Brent!
On Mon, Jun 7, 2010 at 8:27 PM, brent wodehouse <brent_wodeho...@thefence.us > wrote: > > > > http://www.space.com/scienceastronomy/titan-life-methane-speculation-100607.html > > Strange Discovery on Titan Leads to Speculation of Alien Life > > By Charles Q. Choi > SPACE.com Contributor > > posted: 07 June 2010 > > New findings have roused a great deal of hoopla over the possibility of > life on Saturn's moon Titan, which some news reports have further hyped up > as hints of extraterrestrials. > > However, scientists also caution that aliens might have nothing to do with > these findings. > > All this excitement is rooted in analyses of chemical data returned by > NASA's Cassini spacecraft. One study suggested that hydrogen was flowing > down through Titan's atmosphere and disappearing at the surface. > Astrobiologist Chris McKay at NASA Ames Research Center speculated this > could be a tantalizing hint that hydrogen is getting consumed by life. > > "It's the obvious gas for life to consume on Titan > [ > http://www.space.com/scienceastronomy/asphalt-lake-life-on-titan-100505.html > ], > similar to the way we consume oxygen on Earth," McKay said. > > Another study investigating hydrocarbons on Titan's surface found a lack > of acetylene, a compound that could be consumed as food by life that > relies on liquid methane instead of liquid water to live. > > "If these signs do turn out to be a sign of life > [http://www.livescience.com/strangenews/070806_GM_life_universe.html], it > would be doubly exciting because it would represent a second form of life > independent from water-based life on Earth," McKay said. > > However, NASA scientists caution that aliens might not be involved at all. > > "Scientific conservatism suggests that a biological explanation should be > the last choice after all non-biological explanations are addressed," said > Mark Allen, principal investigator with the NASA Astrobiology Institute > Titan team. "We have a lot of work to do to rule out possible > non-biological explanations. It is more likely that a chemical process, > without biology, can explain these results." > > "Both results are still preliminary," McKay told SPACE.com. > > To date, methane-based life forms > [http://www.space.com/scienceastronomy/090625-am-titan-chemistry.html] are > only speculative, with McKay proposing a set of conditions necessary for > these kinds of organisms on Titan in 2005. Scientists have not yet > detected this form of life anywhere, although there are liquid-water-based > microbes on Earth that thrive on methane or produce it as a waste product. > > On Titan, where temperatures are around minus 290 degrees Fahrenheit > (minus 179 degrees Celsius), any organisms would have to use a substance > that is liquid as its medium for living processes. Water itself cannot do, > because it is frozen solid on Titan's surface. The list of liquid > candidates is very short -- liquid methane and related molecules such as > ethane. Previous studies have found Titan to have lakes of liquid methane > [http://www.space.com/scienceastronomy/091221-titan-flash-lake.html]. > > Missing hydrogen? > > The dearth of hydrogen Cassini detected is consistent with conditions that > could produce methane-based life, but do not conclusively prove its > existence, cautioned researcher Darrell Strobel, a Cassini > interdisciplinary scientist based at Johns Hopkins University in > Baltimore, Md., who authored the paper on hydrogen appearing online in the > journal Icarus. > > Strobel looked at densities of hydrogen in different parts of the > atmosphere and the surface. Previous models from scientists had predicted > that hydrogen molecules, a byproduct of ultraviolet sunlight breaking > apart acetylene and methane molecules in the upper atmosphere, should be > distributed fairly evenly throughout the atmospheric layers. > > Strobel's computer simulations suggest a hydrogen flow down to the surface > at a rate of about 10,000 trillion trillion molecules per second. > > "It's as if you have a hose and you're squirting hydrogen onto the ground, > but it's disappearing," Strobel said. "I didn't expect this result, > because molecular hydrogen is extremely chemically inert in the > atmosphere, very light and buoyant. It should 'float' to the top of the > atmosphere and escape." > > Strobel said it is not likely that hydrogen is being stored in a cave or > underground space on Titan. An unknown mineral could be acting as a > catalyst on Titan's surface to help convert hydrogen molecules and > acetylene back to methane. > > Although Allen commended Strobel, he noted "a more sophisticated model > might be needed to look into what the flow of hydrogen is." > > Consumed acetylene? > > Scientists had expected the sun's interactions with chemicals in the > atmosphere to produce acetylene that falls down to coat the Titan surface. > But Cassini mapped hydrocarbons on Titan's surface, it detected no > acetylene on the surface, findings appearing online in the Journal of > Geophysical Research. > > Instead of alien life on Titan > [http://www.space.com/scienceastronomy/090625-am-titan-chemistry.html], > Allen said one possibility is that sunlight or cosmic rays are > transforming the acetylene in icy aerosols in the atmosphere into more > complex molecules that would fall to the ground with no acetylene > signature. > > In addition, Cassini detected an absence of water ice on the Titan > surface, but loads of benzene and another as-yet-unidentified material, > which appears to be an organic compound. The researchers that a film of > organic compounds are covering the water ice that makes up Titan's > bedrock. This layer of hydrocarbons is at least a few millimeters to > centimeters thick, but possibly much deeper in some places. > > "Titan's atmospheric chemistry is cranking out organic compounds that rain > down on the surface so fast that even as streams of liquid methane and > ethane at the surface wash the organics off, the ice gets quickly covered > again," said Cassini team scientist Roger Clark based at the U.S. > Geological Survey in Denver. "All that implies Titan is a dynamic place > where organic chemistry is happening now." > > Speculation 'Jumping the Gun' > > All this speculation "is jumping the gun, in my opinion," Allen said. > > "Typically in the search for the existence of life > [ > http://www.space.com/scienceastronomy/alien-life-needs-more-than-water-100520.html > ], > one looks for the presence of evidence -- say, the methane seen in the > atmosphere of Mars, which can't be made by normal photochemical > processes," Allen added. "Here we're talking about absence of evidence > rather than presence of evidence -- missing hydrogen and acetylene -- and > often times there are many non-life processes that can explain why things > are missing." > > > -- "If all the world's a stage and we are merely players, who the bloody hell wrote the script?" -- Charles E Grant http://www.youtube.com/watch?v=fQUxw9aUVik
