"Life as we know it" defines how we think about habitable planets only in terms of planets that might be habitable by man or something we have here on Earth. Since we are dealing with a sample size of one, it's hard to tell what a habitable planet might be to something else. Earth could be poisonous to them. The first forms of life on Earth originated in a much different ecosphere, something we couldn't survive in. Until early life oxygenated the planet what we think of Earth life today couldn't exist.
The process of evolution of life on another planet and that life's effect on the ecosphere could produce very different results.
Go and have another beer, Grog Mod.
- Orac Zen
new motto: So many Lounge bars, so little time.
At my age you take what you can get. Or invent.