Down the bottom of that Wiki page, are several references to a major paper, (book actually), authored by the "Committee on the Limits of Organic Life in Planetary Systems, Committee on the Origins and Evolution of Life, National Research Council" its called: "The Limits of Organic Life in Planetary Systems; The National Academies Press, 2007".
All of the questions you have so far posed, Carl are covered in some way, shape, or form in this publication. Its purpose was primarily to provide guidance for NASA on the search for exo-life. The table of contents
is here.
Of particular interest is the Chapter on
"Strategies to Mitigate Anthropocentricity".
Here's a quote from that Chapter:
Quote:
Finally, the committee considered more exotic solutions to problems that must be solved to create the emergent properties that we agree characterize life. It considered a hierarchy of “weirdness”:
- Is the linear dimensionality of biological molecules essential? Or can a monomer collection or two-dimensional molecules support Darwinian evolution?
- Must a standard liquid of some kind serve as the matrix for life? Can a supercritical fluid serve as well? Can life exist in the gas phase? In solid bodies, including ice?
- Must the information content of a living system be held in a polymer? If so, must it be a standard biopolymer? Or can the information to support life be placed in a mineral form or in a matrix that is not molecularly related to Darwinian processes?
- Are Darwinian processes and their inherent struggle to the death essential for living systems? Can altruistic processes that do not require death and extinctions and their associated molecular structures support the development of complex life?
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After a hundred pages or so, and eight Chapters, the final conclusions/recommendations
are here.
It seems to me that the MSL/Curiosity Rover technologies are a direct flow-on from these recommendations.
There has been a lot of consideration of all the aspects you raise .. and then more.
The conclusions have given rise to the technologies being sent along with MSL/Curiosity.
There's very few questions left in my mind that the Mars probe is maximising the chance of detecting recognisable bio-signs, in the most probable Habitable Zone presently accessible, and known to humans.
The definitional scope of this 'experiment' is sufficiently tight to enable very specific conclusions, within the practical constraints of the mission. The instruments themselves are designed to return precise results to minimise measurement uncertainties and rule out inaccurate readings.
What the conclusions of the measurements will be, depends on the data, and the conditions under which it is gathered.
One possible outcome could quite easily be, in the case of "no-organic chemistry bio-signs detected" in this high probability HZ, that there are indeed, "no-organic chemistry bio-signs detected" in this high probability HZ, of a high probability HZ planet.
If this were to happen, I would suggest a big re-think of HZ definitions in terms of environment, biologies, search strategies, missions, and detection technologies, would be a very rational outcome.
The opposite findings, I would think, would probably be sufficient to justify a manned mission at some stage in the future.
Cheers