Thomas Green
Mon, 03 Mar 2003 13:31:49 -0800
Using armchair handwaving, I think Bruce's orginal statement stands just fine. Limit energy input and biodiversity decreases. The further you move a cave ecosystem from surface energy, the less diversity of its organisms and the more regression occurs in the organisms that manage to adapt. How many complex organisms are found in the interior of antartica? Extend this reasoning to what is currently known about Europa.
Unless Europa has gobs of seafloor vents spewing some tasty minerals (which is not currently predicted), radiation sputtering is all she has for a primary means of generating "food". To move this food from the surface to the ocean requires some efficient subduction, otherwise nutrients come in a rare meltthrough event instead of a steady trickle.
So start with a sub-par, limited energy source. Then consider the limited means to transport it to the ocean. Occam's razor relegates discussions of complex organisms being able to survive on Europa as speculation at this point; no expert in biochemistry required.
It's important to remember that despite the vast volume of Europa's ocean, it's gonna be *much* more dark and desolate than any environment here on our incredible earth.
-----Original Message-----
> That being said, it's very unlikely that Europan life has even become
> multicellular, let alone intelligent. The stumbling block seems to be
> that multicellular organisms need a concentrated energy source -- and
> so they didn't evolve on Earth until cyanobacteria had pumped enough
> free oxygen into the atmosphere. Animals, of course, need it
> directly. [snip]
This is one of the very few cases where I am going to assert that Bruce is very ill-informed. I am seated at my desk with a copy of the 6th edition of Brock and Madigan's "Biology of Microorganisms" looking at page 718 on which there is a photomicrograph of a bacteria known as Anabaena with a heterocyst in a collection of similar organisms. The heterocyst performs nitrogen fixation for its nearby bacteria in an anaerobic environoment in what is largely an aeobic environment. Bottom line -- many bacteria are aerobic. Nitrogen fixation can only occur in anaerobic environments. Bacteria will form complex (cooperative) networks to optimize the use of both aerobic and anerobic environments.