Just because the universe is vast doesn't mean you can conclude that it's impossible for there not to be aliens. I don't believe in the aliens existence because I haven't seen any reason to. If I see some evidence or an event that makes me question aliens existence then I'll reconsider my belief, but until then aliens are pure science fiction in my eyes.
Originally posted by Draco69
To BackFire:Protists and bacteria used to exist on Mars. Presumably they no longer exist.
Oh ok, in that case I did hear about that. I thought you meant advanced organisms. And when you mentioned that an event wiped them out I imagined a huge matian war going on on Mars.... too much Star Wars for me.
Life in outer space?
Probably. According to professor Michael Russell from Scottish Universities Envoronmental Research Centre life will emerge rather fast near alkaline hydrothermal smokers, if the right soup of chemicals and convection is present.
All you need – basically – is plate-tectonics.
Will it be carbon-based?
Probably. Carbon has the ability to make long STABLE molecules, and to even start making something as remarkable as DNA, you need stable molecules. Sure, there are other elements who can make long molecules, but they are far less abundant in the Universe than carbon and the molecules they make are not as STABLE.
A topic in exobiology these days is : WHAT is life? How do we draw the line between pre-biotic biochemistry and biology? Metabolism? Well, metabolism is just a special kind of chemical reaction. Autonomy. Yes, life seems to be bio-chemical reactions inside a shell of some kind.
This far the only exo-planets we’ve found are Jupiter-giants, and life probably can’t exist there. The conditions are simply too hostile for the creation of the long, complex molecules you need to make life.
But soon we’ll be able to look for Earth-like rocky planets. And look for them in the habitable zone, the region around a star where water exists as vapour, liquid and solid. You need a liquid of some kind to have elements float around and MEET and make molecules.
Try and look up Drake’s Equation.
Intelligent life? Sure, the latest Drake Equation calculation I saw said there could be some 400 intelligent civilisations in the Milkyway alone, capable of interstellar communication. Unfortunately we’re on an average far far away from each other, and the Earth is so small, they’ll have no chance of detecting us, unless they’re so close they can hear our radio/TV signals – that is only with some 80 light-years from Earth, and the Milkyway is some 100.000 lightyears across.
You can also ask: WHEN could the first intelligent civilisations arise? Right after Big Bang you only had hydrogen and helium, so the Universe had to go through a few generations of stars and supernovas before the heavier elements were formed. And life on Earth consists of a lot of different elements.
So – who knows, maybe we’re among the first intelligent life-forms to emerge.
Draco69> There is still no PROOF that life existed on Mars at some point in time. It probably did, but to say it CERTAINLY did is not true at the moment.