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Originally Posted by CraigS
.. Well, I did say, "Can you name one place on a planet" … as distinct from " in a planet" 
Clearly, the proportion of of life bearing locations on the surface of this planet, completely swamps any locations where life may be absent and this then sets the criterion for sampling the surface of Mars. |
Well, let's not get into semantics here
You can't use the Earth as a sampling criteria for another planet simply because of the differences which which each planet exhibits. That's why trying to extrapolate from one given example is dangerous, scientifically, and statistically meaningless. You get skewed and inaccurate answers. Or you get the wrong impression about what's going to occur....i.e. your theories are predicated on a set of assumptions which may or may not even be applicable in the circumstances. Nature doesn't follow the scientific method, nor does it have to follow any set of assumptions made by anyone, nor does it have to follow anyone's expectations. That's what makes this kind of exploration interesting. Don't discount anything, just because it doesn't meet your previous assumptions and expectations.
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Originally Posted by CraigS
How much is 'a good deal', and what would be ‘a statistically significant number’ of samples ... and what is the scientific basis for estimating this?
How much of the surface of a life bearing planet supports life, and what does this tell us about how much of the surface has to be searched ?
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That's about as inane as saying "how long is a piece of string"...it can be as long as you like, or not. It all depends on your definition of what a reasonable amount of coverage is going to be, based on the limitations of your study, but it would most certainly be more than one sampling location. That would tell you very little, either way. However, if you had, let say, 10 or so locations spread widely over the surface of the planet and you were getting results from all of them, either way, then you could make some conclusions from that. But the more you sample, the better your results and the stronger your conclusion can be. If you were getting ambiguous results no matter what you did, then you would have to reevaluate your previous assumptions and your theories and try another tack.
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Originally Posted by CraigS
I think I can see that you'll never be satisfied with any negative finding returned by a robotic probe. What would be your stance if it returns a ‘positive’ result and what is the scientific basis for this ?
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Robotic probes are a "suck it and see" proposition. They limited by their capacity to do only that which they're programmed to do and they can't take advantage of the unexpected or "leap over logic" to look in new and different ways. They can only do what they're designed to do and if the designers get it wrong to begin with or their assumptions about what to find are biased in any way, then the results returned will reflect this. The Viking probes were a prime example of this. They got the results they did because they didn't understand Mars and their assumptions as to what would be there and how they were going to go about testing them were faulty. They produced ambiguous results....yes/no/maybe. Even if the present mission produced positive results, I would still want hands on confirmation and study of a much wider set of samples before I was ready to make a conclusive statement either way. If I was to find irrefutable evidence for fossilised life on the planet, then the case would be closed. If I found nothing after running many tests and sampled a good proportion of the planet, then it would be the same deal. If that sampling meant hundreds of rock samples and many drill cores from a dozen sites or more, then so be it. That's what it will take.
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Originally Posted by CraigS
We can only work with the tools/technologies we currently have, and are able to send there. The framing of the mission goal is important here, because it is, for all intents and purposes, the definition of the ‘experiment’. The results and conclusions of that experiment should be expressed in terms of whatever they set out to accomplish ... as defined in the wording of those goals.
(Sounds like another post, to me .. see my next one).
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The present set of tools is inadequate for the task. All they can do is give us a few extra bits of information with which to prove up our previous assumptions a little bit better than what they are at present. They will not give us a definitive answer. You may have a friend overseas that you correspond regularly with over the internet via webcam. You may get to know them reasonably well but you'll never know what they're really like until you actually go over and meet them in person. That's when you get your definitive answer. It's the same here.
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Originally Posted by CraigS
Anyway, we should review this aspect once the thing gets there and starts producing results .. we have no idea of what will happen .. it may not even make it to the Crater, anyway.
Cheers |
Not in one piece, at least