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Fraser
2007-Aug-09, 05:34 PM
One of most intriguing, and controversial, theories astrobiology is the concept of Panspermia. This idea proposes that life on Earth might have began on another planet, or maybe even out in interstellar space. ...

Read the full blog entry (http://www.universetoday.com/2007/08/09/an-experiment-to-test-panspermia/)

thothicabob
2007-Aug-10, 01:56 AM
Well, the thing is, too, that even if it IS shown that life can survive such conditions AND it can survive the 100's of thousands to millions (or bllions?) of years in space, that still doesn't prove that life DIDN'T originate on earth (or any other planet).

It is an interesting idea though, and one can also wonder what can happen when an indigenous and "foreign" lifeform interact in a planet's environment. Would the native one be better adapted to survive such an encounter, or be vulnerable to the new characteristics of such introduced life? Would they necessarily compete with each other for resources, or would they be able to (or even as a matter of course) find their own niches and co-exist?

3rdvogon
2007-Aug-10, 07:45 AM
Well, the thing is, too, that even if it IS shown that life can survive such conditions AND it can survive the 100's of thousands to millions (or bllions?) of years in space, that still doesn't prove that life DIDN'T originate on earth (or any other planet).


Speaking as one who is highly sceptical about Pansermia I still think the experiment is worth trying out. Though I feel it is something that may need to be repeated several times with different types of rock.

If the bugs survive the Panspermia advocates will say it proves their case. Where in reality all it proves is that microbes can survive being shot into space and re-entering if contained in a particular type of rock. That will then open up a new debate as to how common that sort of rock is on other exoplanets. Also one success does not prove that it will work every time. As most Panspermia sceptics (like me) point out just because intelligent life happened here it does not make it common across the universe - it just proves it happened here and we might be the one in a billion lucky planet.

Therefore this experiment would need to be repeated dozens of times in order to get an accurate estimate as to how often microbes can survive this sort of adventure and if a wide or narrow range of rock types are suitable as carriers.

Sorry if that sounds both tiresome and expensive but if you are going to do Proper Science, then you cannot take short-cuts and make grand assumptions based upon small data samples

Ronald Brak
2007-Aug-10, 09:41 AM
We can stick rocks in a vacuum chamber with a sun lamp and some radioactive material in it here on earth. This may be a little cheaper than shooting rocks into space, although a little less authentic. We have examined plenty of rocks that have fallen from space so we know what reentry conditions are typically like and gravity is an insignificant force when you're a microbe.

But I'll mention that we sort of already know what will happen to bacteria typically found in a rock under such conditions. They die. But then, technically only one single celled life form need survive to colonize another planet.

transreality
2007-Aug-10, 02:05 PM
launch by rocket is going to by relatively gentle ride compared to something launched by bolide impact, still it will be interesting to see the results.

Ronald Brak
2007-Aug-10, 02:19 PM
A bacterium is a punching bag. It's constantly being smacked around all the time by surrounding molecules. If you look at one under a microscope you'll see the little thing can't stay still. That's because it's constantly being beaten up by water molecules or the molecules of what ever medium it's in as they slam into it. If you smack a rock against a wall as hard as you can, a bacterium inside won't even notice. Now a fast enough acceleration will destroy a bacterium, but it would have to be one heck of an acceleration. Since crystal structures inside meteroites (including mars and lunar ones) have apparently survived huge accelerations, I imagine an endospore (bacteria spore) could survive the acceleration as well without a problem.

Drbuzz0
2007-Aug-14, 07:13 AM
The idea is interesting, but I fail to see how saying it is possible for microbes to, in theory, survive the ride, would make it "proven" beyond "Well, it could have maybe possibly happened."

Basically what this would seem to claim is that rather than arising on its own on earth, life emerged somewhere else, or perhaps had existed somewhere else for a great deal of time, and then was blown out into space, presumably by a massive impact. It survived the impact which somehow did not melt the entire thing, and then floated through space for a long long time, only to, by sheer chance, end up hitting earth, surviving the reentry, surviving the impact, and being either suited to, or adaptable to, the conditions of earth.

Seems like a long shot. Even if it could be proven "not impossible."


And if so, where did these microbes come from? Did they first arise on mars? or venus? or in some chemical reaction on a comet? Or did they arise far outside the solar system and travel for billions and billions of years, through interstellar dust and cosmic radiation...

Looking to the solar system, it seems to me that the place which probably had the best conditions for complex organics and eventually life to arise is earth... not somewhere else.

And remote as it is that it could have arisen somewhere else and continue there now, it is even more remote that it traveled there from earth in some major impact event.

Doesn't mean it didn't happen... just seems a long shot. But how could it ever be more than a hypothysis? I see no way it could be proven beyond "not entirely impossible" not to the point of "it probably actually happened"

thothicabob
2007-Aug-14, 04:07 PM
Hmm. I see your point, but at last count, there are at least 5 environments in the solar system where life could concievably have arisen on its own either currently or in the past. It's not unreasonable to expect microbes sufficiently protected to survive 10's of thousands of years in space, hence the theory does have SOME merit; such a microbe finding it self suddenly in a very accomodating environment could really thrive.

Of course, it's just as possible that the new environment would be toxic to it, however the simpler the organism, i think the less sensitive it would be to variations in certain environmental conditions as well, so one could argue that there's a bigger chance that, if very primitive life (or even replicating molecules) made it to earth from somewhere else, it's quite likely they'd be able to thrive and evolve, adapting to the local environment much more easily than more complex forms of life (if we tossed Hillary into the ocean under Europa's surface, she'd likely not last long; we toss an equivalent mass of microbes from there (Europa) into the East River in NYC, many would likely have a better chance at surviving, despite all the other fun ingredients to be found there).

My problem with the theory of panspermia has more to do with my ignorance in the physics of interplanetary travel - I doubt material from an impact on Mars sufficient to eject large chunks of Mars out of its own gravitational influence would find its way to earth in a mere few 10's of thousands of years. I'd expect it would be hundreds, if not millions, of years. While possible, I think the numbers in terms of volume and movement are just 'so great' that the odds are pretty long in terms of such things happening, and if that is the case, how long COULD such microbes or even replicating molecules survive in a functional state in such condition?

[Note: I am not saying it doesn't happen - we 'know' material from Mars makes its way here, or at least we are pretty sure. But the time it takes to get here is the question for me.]

GBendt
2007-Aug-23, 08:20 PM
If life came from space, sheltered inside pieces of rock that came from other places, we should be able to find it in these rocks even today. Perhaps the number of weird species should be rising, if this were the case.

The experiment to be carried seems not very reasonable to me, as various pieces of rock that came from Mars and the Moon were detected on earth, and from their structure we know the temperature they had inside while they descended through our atmosphere: Bacteria would have survived that temperature with ease.
This Orkney piece of rock contains earthly bacteria that will be found thriving in it as soon as the rock is recovered and secured, but what real news can it provide?

Bacteria from earth have survived for years inside the surveyor probe´s video camera that was recovered from the moon by the apollo 12 crew. These bacteria survived the vacuum on the moon´s surface, heated in the sun up to 140°C for a fortnight, and cooled down to -140°C for another fortnight, and all again and again, within the intense radiation from space, for many, many months.

Regards,

Günther

ZaphodBeeblebrox
2007-Aug-23, 10:47 PM
If life came from space, sheltered inside pieces of rock that came from other places, we should be able to find it in these rocks even today. Perhaps the number of weird species should be rising, if this were the case.

The experiment to be carried seems not very reasonable to me, as various pieces of rock that came from Mars and the Moon were detected on earth, and from their structure we know the temperature they had inside while they descended through our atmosphere: Bacteria would have survived that temperature with ease.
This Orkney piece of rock contains earthly bacteria that will be found thriving in it as soon as the rock is recovered and secured, but what real news can it provide?

Bacteria from earth have survived for years inside the surveyor probe´s video camera that was recovered from the moon by the apollo 12 crew. These bacteria survived the vacuum on the moon´s surface, heated in the sun up to 140°C for a fortnight, and cooled down to -140°C for another fortnight, and all again and again, within the intense radiation from space, for many, many months.

Regards,

Günther
ONE Bacterium ...

And it Wasn't in Vacuum, it Was Immersed in a Siingle Drop of Water ...

Sorry, Juust Had to Nip that Lil' Sciience Urban Legend Before it Got Loose in Cyber-Space, Again!

tony873004
2007-Aug-29, 10:37 PM
As far as something travelling from interstellar space and hitting Earth, the numbers are pretty much against it. We've never observed anything exosolar travelling through our solar system. And millions of exosolar things would need to travel through for every 1 that hits Earth.

Just because a rock gets blasted off the surface of a planet and travels 4 or 5 light years doesn't mean it encounters another planetary system. Aim is very important. It probably needs to travel several million light years on average before whizzing through another planetary region, taking a millions-to-one chance that it will collide with anything in this rare encounter.

Cougar
2007-Aug-30, 02:59 PM
There are certainly organic molecules floating around in interstellar space, not just on other massive bodies. Life on Earth seems to have emerged as soon as the surface cooled enough to allow it... or possibly sooner [see thermophiles] (http://en.wikipedia.org/wiki/Thermophile). But it's not like the early Earth needed space-borne organic molecules. It had plenty already. (That's where it came from, after all.)

But all life on earth appears to be related, with a common original "ancestor". Of course, the DNA difference between humans and chimps is only a percent or two. At the same time, the DNA similarity between animals and plants (http://www.madsci.org/posts/archives/2000-11/974689192.Ge.r.html) is striking. So go ahead, hug a tree. They're our cousins. :surprised