(June 19, 2011 at 7:53 pm)Moros Synackaon Wrote: It is conceptually ridiculous to think that the maintenance for life is a requirement/modus operandi for the Earth. It isn't.
Mars is evidence enough for the road not taken.
The Great Oxygenation Event was devastating to existing life back then -- in fact, it would seem to certainly be the end of the world for a great many anaerobes.
The Earth, like any other celestial object, simply is.
In addition, the timescale for the deep ocean to respond to atmospheric forcing is on the order from decades to millennia -- we don't understand why the time scale is so loose, only that we can predict certain events due to knowledge of the thermocline and rough saline distribution.
Abiogenesis and panspermia (what I can think of off the top of my head) would most likely be responsible for life forming under a set of initial conditions -- whether life adapts "fast" enough is left purely to the success and failure of any set grouping of life forms. Past that, there is little to state about a planet and it's ability to "support life". Recent papers by Dr. Christopher McKay et al have indicated that the possibility for life existing on Mars during certain timeframes is quite real -- yet no one would argue seriously that Mars is hospitable to "life as we know it" (perhaps though for life as we don't know it)
In short, life does have a noticeable effect on this planet. However, it doesn't maintain any form of homeostasis by intention.
The Great Oxygenation Event is a wonderful example of such.
I am afraid I disagree with both your interpretation of what the Gaia hypothesis is, and your opinion of what it says.
1. Gaia hypothesis is not some spiritualist mumbo jumbo assigning intention and purpose to natural systems despite how new age air heads would like to interpret it. In fact its core is so constructed as to be susceptible to scientific inquiry. It postulate mechanisms which are susceptible to observation, and makes prediction which are susceptible to verification. One might argue whether it was the most parsimonious hypothesis that can be imagined that seeks to explain what it initially sought to explain, but it is at least capable of being in the running as model of how the biosphere had worked.
2. The fact that other potential biospheres had appeared to fail does not require a special exemption under the Gaia hypothesis. In fact Gaia hypothesis, if worked out in detail, would predict that the same fate would before the earth as the biofeedback mechanism will unavoidably fail when the moderating agent of CO2 in the atmosphere will eventually be exhausted as it is sequestered by the biosphere to compensate for ever warming sun, and the biosphere would then irremediably collapse, and the ocean will evaporate, it's water dissociate, carbon sequestration then reverse, and the earth become like Venus.
