Where did we come from?

WIZE wrote: »

So where did life come from then ?

I come to the conclusion that life was on another planet that exploded some where out there and a piece of that planet ended up on earth to create life here

But as others have said then youre left with the question of where did that life start in the first place?

What I dont get though is why life in any way has not adapted its self on any of our local planets

Well we don't know. Yet. Higher life forms need fairly specific conditions over very very long periods of time to form. It seems going by the earth anyway that bacterial life needs a couple of 100 million years to kick off. Then again Earth is very unusual. For the solar system anyway. Its the only one with plate tectonics. It has a very specific chemistry because of the impact that formed the moon. It had a thick dense atmosphere very early on, but one that thinned out in the "right" way, didnt blow off into space like mars, or get hotter and denser like venus. It has liquid water on its surface. It has an active core that provides an sheild against radiation. We also have a moon. The largest moon in comparison to the home planet in the solar system. It gave us huge tidal forces in the distant past which some surmise helped certain life processes along. It's a very long list.

Now Mars could well have bacterial life or had it in the past. It is a rocky planet and did have liquid water on its surface for a time. How long that was around or how stable it was is still unknown. The majority of water carved features on mars look like flash flood features, not stable water systems. When the core died, so did mars. Too small to keep an atmosphere so most of that blew off into space. Contrary to what has been said earlier there is no liquid water on the surface of mars today and hasnt been for a very very long time. Its possible that deep under the surface highly saline water is somewhat liquid but that's conjecture.

Mars looks so familiar to us. Its the most familiar place out there discovered so far. Its got mountains and sky and wind and sunsets etc so it seems more hospitable than it actually is. If you were to stand on Mars and by magic could stand there without a spacesuit, the first thing you would notice is how dim the light is. much like dusk on earth. The second thing you would notice is the cold. Then you would feel how thin and dry the air is. You would barely feel a 200 mph wind on your skin. The solar radiation would hit next in the form of very strong UV. All in all if you wanted to design a place that was built for sterilising bacteria you could do worse than come up with mars. On the surface at least.

dvpower wrote: »

Not a good answer anyway. It only opens up the question about where the higher being came from (and so on, and so on...).

Some people will say that there was an ultimate higher being that was always here (I think they refer to it as God), but its probably better just to say that we don't know.

True. Could a God exist? I would say yes. You could imagine all sorts of different scenarios where one might. From the notion of a dumb force that brought the universe into being from "outside" through to an internal force that guided the formation. You could look at the universe as a giant information bubble, with a set of rules that govern that information. Those rules could be god. In which case physicists are better theologians than clergymen You could further argue that the complexity of this information could reach a certain point where it became conscious. Not in our sense, it would be as alien to us as we are to an ant. If you look at an organism, it's made up of individual cells reliant on the whole, but also independent organisms themselves. If a blood cell was self aware it would relaise it was an organism, that there were others around it, some the same many different, but it would likely miss the person walking to the bus that its part of. Intelligence and consciousness arises out of these structured colonies. When you regard the web of life just on this planet we may be part of a whole that we're only partially aware of. Extend that to the universe. We could be part of an infinitely more complex universal Gaia. We or others like us out there may even get to the point where we can create other universes in the lab. In which case we would be the "gods" of other universes and the reproductive system of our own.

maninasia wrote: »

Wibbs, good points.
But it must be emphasised that the vast majority of life on earth may be living within the sub-surface zone (bacteria).

Very true. Indeed single celled and very "simple" life makes up the vast majority of life on this planet. Sharks and lions and us are a teeny tiny part of the whole. Almost an afterthought.

Plate tectonics, athmosphere, low temps etc..doesn't mean anything to bacteria that evolved for conditions on Mars.

True, but lfe as we know it, based on carbon and utilising chemicals or the sun for energy need certain criteria to survive, much less evolve. And that criteria is quite narrow. One biggy is liquid water. Even in tiny amounts. Without liquid water life may survive in stasis, but won't be active life and its highly unlikely to evolve in the first place. One theory that requires our large moon, is some processes of pre life require liquid water, others require the complete absence of it. The creationists love that one, but IMHO its bollox. In the moon theory the very aggressive tides of our early world, when the moon was much closer, drowned and alternatively baked compounds on some ancient beach. If this is the case, then a planet without a large moon will be at a serious disadvantage. In the case of a water world like the conjecture about europa, no drying our is possible, so again would be less likely to kickstart life.

We must be careful to not fall into the 'Earth is just right trap'. Earth is just right, for living things that evolved on Earth. This is self evident, no?

Yes and no. The only life we know of is earths. Now it seems earth was the right place for the life we find here. But and its a big but, if life kicked off so easily as it seems to have done here, then why is all life on this planet related and appears to have had a one off event as a startpoint for all life. There are no "aliens" among us thus far discovered. If life can kick of so readily on suitable planets then one would expect it to have happened more than once here, on a planet clearly suited for it. Lots of times in fact, but it seems it didnt. This would suggest to me at least that life, certainly on earth is quite the fluke. Complex life is even more of a fluke. For longer than complex life ruled, single celled goo was the order of the day on earth and is still by a large factor the most common life here.

It would certainly not be just right for living things that evolved on Jupiter or Mars. Basing our conclusion on life on Earth is very short-sighted. We know that Earth seems to be more stable and seems to support more complex life especially above the surface but we don't know if it is any more suitable than Mars for subsurface bacterial life.

Ok lets say we engineer a bacterium to grow on mars. Make it very resistant to radiation, with the ability to utilise CO2 and other elements as fuel and with the ability to survive for long periods of time without liquid water(if there is any anywhere on mars deep down). It would be doable I imagine. That's OK, but would it spontaneously evolve on mars in the first place? With a very different set of criteria and pressures involved? I doubt it, unless mars had water for far longer than thought of and that loss of water was slow enough that said life adapted rather than died out.

TBH though we'll never know, I suspect Venus 3 billion years ago a more likely candidate. It had a very dense CO2 atmosphere, like we did at first and also likely had liquid water. It had the gravity to hold onto an atmosphere and the active core to drive it. It seems if life did kick off there it wasnt strong enough to terraform the atmosphere as it did here, or being closer to the sun the heat was just that bit too much.

BTW, the date for complex life to emerge has been put back by another few hundred million years recently with discovery of fossils in Australia
http://www.kotaku.com.au/2010/07/multicellular-life-it-might-be-older-than-you-think/

Oh I agree it did kick off very early. But while it's easy enough to say that this means its inevitable that life will start, its also equally easy enough to say that life was a fluke, that required very specific criteria to occur and its not that common out there. Until we find life, any life, beyond our planet we have an example of just one. All we can surmise is that going by current knowledge it would only happen on a planet near identical in makeup to our own. Anything else while interesting to think about is pure conjecture.