All living things on earth have DNA, a marvelous molecule which has produced untold millions of species which inhabit every corner of the globe.  The question of where life came from - whether it develooped on earth or came from space - is really quite silly, because we are "space" as much as space is.  Everything "out there" is also "here", and vice versa.  Organic molecules are formed naturally on Earth, but we are also showered by meteorites which carry organics.  Add to this the discovery that the Orion Nebula is an "organic-molecule factory", producing "precursors to life-enabling molecules", and you have a space broth of pre-biotics seeding other worlds.  Assuming that the Orion Nebula is no the only  organic factory out there, one can only conclude that life is common and ubiquitous.  And if this mix of conditions, over billions of years, produced the most adaptable molecule for life on Earth, why would we think that it would be otherwise on other planets?

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As far as we know DNA/RNA are the only self replicating molecules. The ingredients for DNA/RNA exist in space, in comets, asteroids and, very likely, on most planets.
If life is found on Mars or one of the moons of Saturn or Jupiter the life molecule might very well be RNA/DNA - but even more astonishing would be that it isn't.
I don't know what the current thinking is about this in the scientific community, but I personally never considered DNA to be anything but unique to this earth. I suppose there is no need to develop Ray-guns anymore - we can just use an insect repellant.
Yes, but you have to remember that no two worlds will be exactly alike, not just physically, but also speed of rotation and revolution. Life also developed in synchrony with with the phases of the moon - So, it is very doubtful that organic evolution would follow the same path on any planet. For some reason the hominin goups came out on top as far as intelligence goes - but on another planet they might not exist at all. I just think that if DNA is universal, then you could say that you're related to a Gloptoid in Quadrant III. The point is that evolution is unpredictable.
There has been speculation that carbon may not have been the only basis of life within the universe. Since I and not a bio-physicist or a scientist, I can only speculate that there may be some possibility of life forms based on, say selenium, which have a theoretical possibility of producing self-replicating molecules and thereby producing another form of life.
I think one of the things that majorly leans towards carbon is the fact that there's so much of it. It's the lowest element on the periodic table in it's category. As you move up the periodic table, each next element becomes significantly more rare than the previous one. Silicon is the next likely candidate, and it's vastly less common than carbon, thus reducing its chances of becoming the base element.
I had forgotten all about that aspect. Thanks for reminding me.
Yay! I made a contribution! :-D
I just watched that movie. Beyond predictable and we saw some Star Wars in there. George Lucas should sue.
My proposition of course is speculation, and I'm not discounting the possibility of life forms other than cabon based. But it amazes me that it's possible that we could be related by the DNA molecule to all living things in the universe
Yeah, I think one of the things that almost all of the science-fiction of the past 70 years has shown in that our species seriously lacks imagination.

Also, silicon lifeforms wouldn't necessarily be crystalline. Carbon is also mostly crystalline, outside of organic molecules. The thing about silicon lifeforms being moving rocks is just a wacky convention from somewhere back in the space sci-fi origins.
I agree. The mechanics of the universe are very predictable and familiar, yet we want something very alien in our Aliens.
Well, actually, I meant that more as a poke at the Star Wars and Star Trek thing where just about every alien race is a different colored human, maybe with some weird shaped ears or some head tails. Either they do that, which I realize is mostly because of budget issues, or they create beings that are completely improbable in the opposite direction. I recall a few alien races that are pure energy or something like that, in a couple of books.

Orson Scott Card came up with something at least reasonable, in 'Ender's Game'. Shame he kind of lost it, a few books into the series.




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