The forth hypothesis supported is the recent paper on an experiment conducted over twenty years in which appropriate precursors were placed into very cold storage. It was found that interesting chemistry occurred over time in the ice fractures.
Text books imagine life been formed in a nasty looking but still hot or hotter environment. It appears much more likely that while hot will certainly exist it will be buried under a mile of water, carbon dioxide and methane ice. That makes visiting this moon a rather likely milestone in our understanding of the formation of at the least, the precursors of life.
http://www.spaceref.com/news/viewsr.html?pid=30293
The Possible Origin and Persistence of Life on Enceladus and Detection of Biomarkers in the Plume
STATUS REPORT
Date Released: Friday, January 9, 2009
The jets of icy particles and water vapor issuing from the south pole of Enceladus are evidence for activity driven by some geophysical energy source
. The vapor has also been shown to contain simple organic compounds, and the south polar terrain is bathed in excess heat coming from below. The source of the ice and vapor, and the mechanisms that accelerate the material into space, remain obscure. However, it is possible that a liquid water environment exists beneath the south polar cap, which may be conducive to life. Several theories for the origin of life on Earth would apply to Enceladus. These are (1) origin in an organic-rich mixture, (2) origin in the redox gradient of a submarine vent, and (3) panspermia. There are three microbial ecosystems on Earth that do not rely on sunlight, oxygen, or organics produced at the surface and, thus, provide analogues for possible ecologies on Enceladus. Two of these ecosystems are found deep in volcanic rock, and the primary productivity is based on the consumption by methanogens of hydrogen produced by rock reactions with water. The third ecosystem is found deep below the surface in South Africa and is based on sulfur-reducing bacteria consuming hydrogen and sulfate, both of which are ultimately produced by radioactive decay. Methane has been detected in the plume of Enceladus and may be biological in origin. An indicator of biological origin may be the ratio of non-methane hydrocarbons to methane, which is very low (0.001) for biological sources but is higher (0.1-0.01) for nonbiological sources. Thus, Cassini's instruments may detect plausible evidence for life by analysis of hydrocarbons in the plume during close encounters. Astrobiology 8, 909-919.
Astrobiology. October 2008, 8(5): 909-919.
