The following ideas have lived in my head for a long time and were initially invoked as a result of understanding the compelling hypothesis put forth by James Lovelock and Lynn Margulis, the so-called Gaia Hypothesis which states that the cumulative effect of the metabolic, physical and chemical properties of living systems on Earth is a cybernetic system with homeostatic tendencies, tightly coupled to the planet's physical surface properties such as atmosphere and geology.
It occurred to me that not only was the core idea of this Gaian system plausible on Earth, but it was probably a signature of a class of life that exists in potentially large numbers of other worlds in the universe. It is unfortunate that a substantial segment of the scientific community still prefers to think of life as a consequential phenomenon with the advent of biological systems being extraterrestrial in origin and the impact life has on sustained planetary habitability and evolution as insignificant. The accepted idea seems to be that life on Earth exists as a result of some cosmic "seeds" planted on Earth during the age of bombardment (early on in Earth's history it was heavily pummeled by asteroids, some presumably carriers of life's essential chemical ingredients) coupled with randomly perfect conditions for "germination".
I, and others, disagree with this notion. Life, as amazing and wonderful as it truly is, is a planetry surface property that is bound both in advent and evolution to the planet upon which it happens. By looking at life in this way (from a systems as well as planetary perspective), the possibility of finding living systems (of the same class as Earth's) throughout the galaxy is very good. In the next 5-10 years we will have the instrumentation to start searching our galaxy for "life like ours" utilizing techniques of atmospheric spectral analysis combined with new telescopes.
In earlier posts I've briefly touched on Lovelock's approach to the detection of life on other planets. Does this life really need to be like ours? If so, to what extent? I argue that there are classes of life that exhibit similar behavior, but need not be composed of similar ingredients or design (like cellular genetic systems). So, then how do you define "life like ours"? Good question.
Life like ours can be defined as an autochthonous geobiological autopoietic cybernetic system. What?
In a nutshell: life like ours is a dynamic system, an adaptive planetary surface property, originating on the planet where it is found (tied to planetary formation and evolution), provides regulatory feedback mechanisms that ensure planetary habitability, and is remotely detectable via atmospheric spectral analysis due to dynamic atmospheric chemical exchange (life like ours perturbs atmospheres as a consequence of the processes associated with the daily business of living). Our class of life is a planetary-scale system composed of sub systems (animals, plants, microbes, cells, viruses, dna) that cumulatively, some more than others, act to ensure that Earth remains habitable for life. For this class of life, the particular composition and associated behaviors of sub systems are implementation details. Again, life like ours is a planetary surface property, just like the atmosphere, land and oceans. Astronomers like to say, and correctly so, that we are made of stars. Narrowing the scope a bit, it can also be said that we are made of Earth.
Can the Earth be used as a general model for rocky planets possessing autochthonous geobiologic surface properties?
Can a planet's surface be favorable for life without supporting autochthonous life forms?
Look into the light.
