[Fyron]

There is a famous equation called the Drake Equation which mathematically sets the probability of life in the universe.

Yes, and it attempts to determine the relative number of life-supporting planets in the universe. So what? It has nothing to do with atmospheres that do or do not support life, or with gases that can be used for energy purposes in organisms.

There is a vast range of types of life on earth - plants, animals, people, viruses, bacteria, etc. Even on earth, we have microbes that exist in the polar ice caps and others in the sulfur vents of volcanoes, neither of which use oxygen and both conditions are deadly to humans.

There are molecules that can replace O2, but some organisms on Earth can use H2, H2S, S, HNO3, H2SO4, and CO2 in lieu of O2. But as I've said before, they just don't make enough energy to be useful for anything more than a bacteria, and in that case, it has to have little or no competition!

This is why I have been careful to always say "complex organisms" instead of just "organisms".

Yes, humans couldn't have evolved without O2, but we would have evolved differently in another atmosphere.

Assuming that is actually possible in the first place.

So there are lots of examples here on earth.

Yes, examples of simplistic organisms that do not need very much energy to survive. All complex earth-based organisms use O2 to get energy. Even plants use O2 to break down the glucose they make to get energy. They just make a lot more glucose than they use, which is why they put out a lot more O2 than they do CO2.

How exactly would Ammonia, Methane or Sulfur Dioxide be used to get energy for complex organisms (not monerans, not protista, not any other forms of microscopic life)?

[ February 20, 2003, 05:57: Message edited by: Imperator Fyron ]