It had to evolve...it can't just keep appearing, it involves millions of years of evolution from amino acids to RNA to DNA to complex single cellular life that protects the DNA increasing survival and therefore bacteria species radiation.

I know that,but lots of them say that asteroids brought life to earth.Its not necceceraly correct but who knows,unless you have a time machine.

There are ways to determine it without needing a time machine, though it is difficult. While you can't really disprove panspermia, one way to demonstrate it's truth (if it is true) is to find an asteroid or comet or other fragment bearing life or proto-life that is basal to all life on Earth (ie, once establishing it's relation to Earth life, ruling out the possibility that it originated here).

Panspermia, while unproven, is a legitimate hypothesis as a part of the history of life on (and off) Earth, but it is not a solution to the origin of life itself.

But do asteroids really contain life? Unlikely seeing as an asteroid can't hold heat, gravity or an atmosphere. Any life we found on an asteroid would be dead from intense freezing or burnt in the collision with our atmosphere.

the bacteria are frozen in a deep sleep for thousands of years till they hit warmer land,then they start awakening,eating and finaly reproducing

Aye? This isn't Doctor Who.

Asteroids and like fragments are not nearly as hostile as some Earth environments in which life can thrive. And these extremophiles are often of the most basal strain of life, not even bacteria, but of the domain Archaea.

But even Archaens (correct me if that's not right,) must do all the seven basic functions and they still have organic material that would not survive plummeting to Earth on an asteroid...even if the asteroid was large enough not to disintegrate into something the size of the a pebble, the meteorite would likely destroy all autochthonic life in impact.

some say life is like a virus,it always adapts,mutates,and survives,many asteroids that fell,delivered bacteria that were frozen on them.Chondrites are the one type that deliver organic materials

Yeah, Evolution was a pretty cool movie.

I love the bit with the shotguns.

In the mall after they killed the dragon-spawn-loogie. Yeeeaahh.

Srsly though... I really hate narrow minded people who say 'No aliens exist'. They assume the word 'alien' means a grey thing that abducts people, despite the fact the term originates from the Latin (or was it Greek?) word 'Xeno' which, most of you will assume, means 'foreign' or 'stranger'.

But more or less, life somewhere in the galaxy, or/and the universe, must be teeming with life, be it animalistic or sentient. Only time will tell...

By the way...try checking out Alien Planet. It's a fictious documentary about finding life on an extrasolar planet. It's on YouTube, if you're interested.

MEXICANS?

I think Darwin IV was a fantastic concept, Wayne Barlowe did a good job making his book so believable.

And I'm not saying there's no alien life, just that no alien life came from any meteorites, then again, ablation dictates that if the outer layers are stripped away and the innards are still cool, perhaps just maybe some extreme life form might survive the impact. But this would only work if the meteorite's resultant explosive impact didn't destroy everything in the vicinity.

there are some bacteria that can survive tremendous heats,just like they found those worms that live underground where miners bearly survive,a perfect example is a cocroach,a nuke cant stop em,heat cant stop them,starving cant stop them,only the human foot can stop em...there are organic materials on asteroids and meteorites,go around wikipedia and search about it.

Erm yes, a nuke will kill a cockroach, in fact a concentration just six times that of the human limit will kill most cockroaches this is because cells only become cancerous from radiation in division and cockroaches cells divide every few weeks when they molt, a world submerged in fallout would still have a terrible effect on our poor little insect friends. In further addition, as a living creature, they still require oxygen to survive and temperatures that don't exceed 150 degrees. Organic materials don't = life as well. There are organic compounds such as amino acids on Titan, (At least this is what scientists speculate) however Titan isn't too far off absolute zero the chances of life, at least on the surface, are small.

an asteroid has a cold surface,but the inside of it doesnt have to be like that,there is water on asteroids equaling that there is O an that means that there might be life on asteroids,just like some planets that were slingshooted off of their star system.

And how would any part of an asteroid stay warm in deep space?

I don't know just how that comes into the equation of things WoF but I suppose if you're just generally asking a hypothetical warm asteroid could get very close to the sun, or have a molten core through immense pressure but then, I would have thought that this was impossible for an 'asteroid.'

Where are you getting all this ground breaking information from? An asteroid is cold well done, as is the vast majority of the vacuum of space. So why would the inside be warmer? What would significantly warm up the inside of an asteroid? Remembering of course that most asteroids are no larger than a brick and only 1100 asteroids known to man in our solar system bigger than 30km in diameter. Also yes there are sometimes trace amount of water on some asteroids...we expect, that doesn't equate to life, otherwise there would be microbes on the moon and almost every other planet we know of. Firstly, yes having water does mean that there is oxygen but then it would be locked up in freezing cold ice...trace amounts of ice, we're talking a few bonded atoms here not puddles.

they are warming up,thats why if a meteor is coming near earth or something bigger,you see a trail,if you use high tech telescopes you can see trails of water,that is melting from the meteors core.Meteors and asteroids that have water and carbon,from that with organic building materials life started to thrive.

If we ever develop a galactic empire, I'd like people to go round dropping 75 cokroaches on every uninhabited planet and see how long they survive. You could take bets! And then end up with a race of super-cockroach-people a few billion years later.

eew,we would have to invent some kind of super anti bug spray if those things were to steal supplies from us

I think we are misunderstanding by your use of terms, do you mean a meteorite warms up? As in meteorite, an asteroid that has entered out atmosphere? If so then yes they do heat up obviously, but how does this explain autochthonic life? Most asteroids are iron rich or silicon compound based, as for the trails of water that follow in the tail of a meteorite, I would expect that these are trace amounts as I previously stated, not enough to give life a kick start.

We must remember our argument, 'that supposedly life could start from an asteroid collision,' [paraph.] I say to you that this is nigh on impossible because any organic compound, amino acid or even RNA living on an asteroid body would cease to exist post impact, even in the initial burn up.

I must admit I kind of like the Idea that we came on the very asteroid that killed the dinosoars, however scrabtrapman seems to be right on this as any frozen life on an asteroid would either burn up or die on impact, unless bullet magnet comes and gives a scientific explanation of how it is possable for life to both exist on an asteroid and survive coming to an atmosphere than I'll have to go with scrabtrapman on this one.

Thank you, I would like to reinforce my point by suggesting that any life so well equipped to the cold, airless void would be ill suited to a sudden burst in oxygen levels and temperature.

That's not the same as being warm. Meteors approaching the sun will be warmer than when they're further away, yes, but that doesn't allow them to be warm all the time, even when they're a long distance away.

Also, you're confusing meteors with comets. Comets have large amounts of ice, whereas meteors are mostly rock. A comet's tail is not caused by the ice melting away, it is because the solar wind blows past the comet and strips ice crystals from the surface.


Scrabtrapman (and others); you're confusing the situation. Meteors don't need to be warm and any hypothetical lifeforms don't need to be pursuing active, motive, life. They could be in deep freeze until they crash land in to a warmer environment.

Ok so he meant comets, right fair enough that's sorted.

But I'm going to say something one last time, any autochthonic life on an asteroid, comet, whatever, will not survive the impact with Earth or even the burn up unless the asteroid is fantastically huge and not all of it even explodes upon impact with Terra Firma.

All that needs to survive is one single bacterium (or whatever the hypothetical lifeforms are). Given that many meteorites have remained freezing cold even after passing through the atmosphere and crashing in to the earth, I don't see it as all that unlikely.

Perhaps, but then the bacterium has to contest with the immediate onslaught of an unnatural environment and competing bacteria. I suppose you would have to factor where this hypothetical meteorite has landed as well.

Nate's right. Touching a freshly landed meteorite with bare skin will give you severe freezer burn. Wait till it warms up.

And bacterial life can survive such a journey. You know why you should not refreeze food? Bacteria which settled on it once defrost are frozen with it, and spring back to life during the second defrost and multiply.

Such journeys may have already taken place. Earth and Mars exchange material all the time. Fragments blown off of one by large impacts drift through the solar system for some time, before falling onto the other. These, and indeed, all meteorites, are most easily found in Antarctica, where they stand out in the ice. This is how all Martian rocks in human possession have been acquired, since none have been returned from Mars.

It's unlikely that alien life transported in this way would survive long, especially if it shares no common ancestry and has different biochemistry (though obviously specific details would need to be known to assert this). The same way artificial life would fare poorly against native flora, and similar to the reason that no second genesis of life has occurred. But on a suitable lifeless world, which is what we usually imagine for Panspermia, a foothold is possible.

For a more terrestrial origin of life, the role of comets and meteorites is that of primary or accessory contributor of the organic molecules from which life could arise.

So perhaps some cataclysmic event that caused a large fragment of Earth to crash into Mars could restart life over there? Surely it works both ways?

Large? I imagine a large fragment would be as cataclysmic to Mars as the original event was to the Earth. No, small fragments. I'm saying that bacteria have likely been seeded on Mars many times during our planets' shared history, and certainly recently with the probes and rovers. It doesn't appear to have taken, or at least, in no place we've looked.

One idea I have heard is that life may have started on Mars during its early and more idyllic phase of existence, and was since transmitted to Earth. But there's no real evidence is support of this over other explanations, as with all panspermia hypotheses.

I just think it's to good to be true, there would be so much life across the stars if this was the case and much of it would have to originate from somewhere. I think life started on Earth in some hot pool like in Yellowstone by simple RNA and from there it evolved.

I don't think that would be the case. Mainly because the universe is just that large, and so few places in it are even potentially habitable even to bacteria.

I'm not supporting panspermia as the actual explanation for Earth, but as a phenomenon it is entirely plausible.

Fair enough. I'm far more interested in how RNA and then DNA came about, also how chloroplasts became symbiotic with plants, did they evolve separately? Who knows.

Like mitochondria, chloroplasts have their own DNA and reproduce by themselves in the cell. And like mitochondria, they very closely resemble some prokaryotes, reproducing by binary fission and having various "cell" chemistry almost identical to bacteria and unlike the equivalents in the rest of the cell. Both appear to have descended from either blundering or adventurous prokaryotes that invaded or were eaten by the ancestral eukaryotic cell, and both cells found a way to adapt to that state. Many of the smaller cell's genes migrated into the nucleus leaving only a skeleton genome behind, and now neither can survive without the other.

Interestingly, there are several living species of single-celled organisms that represent actual intermediate steps in this process, including one that has to catch and retain cyanobacteria to serve as its chloroplasts.

This is called endosymbiotic theory, and a similar one (viral eukaryogenesis) postulates that the nucleus is derived from a large DNA virus that invaded an archaean cell and assumed total control.

You'd be so awesome as a biology teacher for sixth form!

So when someone catches a virus, it's really just the viruses taking a return on their evolutionary investment...

I'm pretty sure flagallae were another little wriggly organism that got subsumed into early prokaryotes.

a flagellum is likely to be an evolutionary accident rather than a 'fusion of two bacterium' because that doesn't make very much sense. These little cells were better at swimming than their counterparts and thus survived better.

i have heard that mars and venus were also having some early life with our planet,but venus got global warming and it went wild,and mars went cold,a rover found something looking like a petrified wood,so there was life on there probably.

I doubt it found a whole petrified wood, also trees have taken many millions of years to evolve, anything still there would be buried under sediment, however shallow.