Photosynthesis on Europa?
I've seen a news item in several science pages about photosynthetic bacteria isolated from deep vents. The vents are so deep that surface sunlight must be negligible; instead the bacteria must be using the faint light emanating from the hot vents themselves. This electron microscope picture (from Beatty et al. )shows the light-collecting device as pale spots near the surface of the bugs.
Finding these bacteria growing in such low light suggests that the lower light limit photosynthesis organism might be very, very low. Even Jupiter's moon Europa might be bright enough. Wow.
UPDATE: Very nice writeup over at The Loom , who, in turn links to Alan Boyne at Cosmic log a MSNBC blog. (The cosmic log link is a bit dodgy; his entry is June 20. )
Seems that everyone took the scanning EM picture of the bacteria. I like the transmission EM better because it shows the antenna structures. Thinking a bit more about this, I think the amount of sunlight falling on Europa is almost besides the point. If hot vents are glowing, then photosynthetic life can be anywhere that has vulcanism and liquid water.
UPDATE#2: Oops, the way Carl and others write it, Europa is chosen as an example of buried hydrothermal vents. I'm not sure where I got the idea that sunlight levels were part of the argument... speak in haste, repent at leisure.