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Hi All,
Hmmm ... all very interesting and educational. Just to set a few things straight ...
Though I am personally of the opinion that intelligent life in our galaxy is very, very rare (ie as I said in the other thread and probably <10 and tending towards very small one digit numbers) out of its 300 to 400-odd billion stars, yes of course we should be looking earnestly!
A find of any life-form (past or present) on Mars while very interesting is not particularly significant for gauging the likely extent of life elsewhere in the Milky Way. We know that it is quite possible for simple bacteria and archaea to make the journey inside rocks that have been blasted off the surface by meteor/comet impacts. I think I read somewhere that Earth receives a couple of kg of Mars every year -- and it works in reverse. Viable bacteria/archaea inside a suitable rock could survive for many tens or thousands of years to land somewhere else and colonise that place. If we found evidence of simple life on Mars, fact is, it is too easily transferred either way for us to easily conclude it arose on both bodies independently without other evidence.
The case for Jovian or Saturnian moons is substantially different. There is virtually no mechanism to transport life from Earth or Mars there or vice-versa. If evidence were found there, then that certainly raises the probability that simple life is ubiquitous in our galaxy (and therefore the Universe as a whole). Obviously this is both where and why we should look. I support the idea of searching wholeheartedly. If it is there does it affect my philosophical or world-view – no. If it isn’t there does it affect my world-view – no. If it is there does it increase the probability that intelligent life exists elsewhere – I think a little bit, but not by that much.
It almost amounts to a massive leap of faith to conclude that if we find bacteria/archaea within the oceans of Europa, that intelligent life is similarly ubiquitous. Plants and animals need a much, much, much narrower range of stable conditions to even stand a slight chance. The first bacteria/archaea arose here at about 800 million yeas after the formation of Earth -- a quite long time. It may have happened a little earlier than this but there is no evidence of it.
The bacteria/archaea of today are essentially unchanged compared to those found in the fossil record from 3.5 billion years ago. They are extremely simple creatures who are robust, hardy and can survive in a wide-range of environments – high pressure, low pressure, high/low temps, underground, underwater, chemicals etc etc. But in themselves they will never learn to mix concrete or sign complicated insurance forms.
It took nearly another 3 billion years till we reach the point where there was (merely) multi-cellular life and then another 750-odd million years before we turn up. During that time there were/are literally tens if not hundreds of millions of species and varieties that did not develop intelligence. We are the only one that has managed the trick and we should never have succeeded according to the biologists (ask Charley Lineweaver UNSW astro-biologist). If you can, take in one of his talks on astro-biology and you will come to appreciate that if we (humans) suddenly die out we won’t be replaced by super-smart kangaroos, gorillas or dolphins in a hurry, or much more likely, ever.
If the eventual development of an intelligent species given favourable conditions is common or even fait’ du complete if you start just a few viable organisms, why weren’t/ aren’t there more intelligent species on Earth? Apart from we humans, even the most advanced and “intelligent” creatures in both present day in the fossil record show no sign of becoming more “clever” during the very long stages of their existence as a species – ie the smartest kangaroos today do not have more developed brains than those from many millions of years ago.
The dinosaurs were the “master-race” of this Earth for hundreds of millions of years yet none of them managed it either. Why? On the available evidence (ie without invoking wishful-thinking or speculation that “life may be different elsewhere”) the only conclusion you could reach is that intelligence is an exceptionally rare trait among advanced multi-cellular creatures – in fact it is so rare that in 3.8 billion years of our history and 10s or 100s of millions of species only one creature made the grade – and we shouldn’t have! If you don’t call that flukey, then what is?
/cont Pt 2 ...
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