Talk:Panspermia

Contents

1 Day of the Triffids 2 Raelism 3 Evidence and mechanisms 4 Arrhenius and Panspermia 5 anthropic principle 6 Panspermia and Big Splash Theory 7 Glycine 8 Faulty Evidence 9 A Touch Optimistic? 10 Late Heavy Bombardment 11 Direct Evidence of Extraterrestrial Life 12 Changes

Day of the Triffids

Citing Day of the Triffids as an example looks wrong to me. As far as I can recall the plot, the triffid seeds were a product of Soviet biotechnology that were accidentally released in the stratosphere. -- Alan Peakall 17:36 2 Jun 2003 (UTC)

In the movie adaptation they were from space.

Raelism

"One cannot help but notice the similarities between this hypothesis, and quasi-religious movements based on extraterrestial beings starting life on Earth, such as Raelism."

You should name some of these similarities, or it is just an opinion. - Omegatron 04:56, Jul 30, 2004 (UTC)

I think the Raelism connections and some of the other references in the SF section are probably wrong. Panspermia is a narrower theory than 'life on Earth originated from outer space'. Specifically it is not the same as intentional colonisation by aliens. Rather panspermia is the hypothesis that the building blocks of life are common and uniform throughout space and that they take root when they land on a planet with suitable conditions. Directed panspermia, is that modification that the reason the building blocks are common would be due to the actions of a past alien civilisation. -- Solipsist 05:23, 30 Jul 2004 (UTC)

The two ideas are very similar, with some differences of course. Both advocate an external intelligent force behind the start of life, and transfer the problem of how life started (creator or not) somewhere else. Directed Panspermia make it random, and only providing seeds. Raelism says it is human only, and targeted to earth. Raelism relies on religious revelation for proof. Panspermia is a hypothesis that is so far unproven. We do not even know if intelligent extraterrestial life exists to begin with, let alone they actually did send the seeds of life. Raelism is advocated by someone who is considered fringe, and based on blind belief mostly. Panspermia is proposed by respected scientists. Other than these differences, you can see that they are pretty similar. Right? Can you see the similarity (and differences) now? Can we agree on a comment that can go back in the article? -- KB 19:07, 2004 Jul 30 (UTC)

Not really. I can see where you are coming from, but the word panspermia is created from the Greek : pan- "all" + sperma, "seed". If Raelism doesn't involve the idea of spreading the seeds of life uniformly throughout the universe it isn't panspermia, but alien colonisation. Panspermia is a serious scientific idea, even if it is not often taken seriously. The most important aspect about panspermia is its uniformity, implying that Earth is in no way special and if the hypothesis is true we would expect to frequently find the seeds of life on other planets, including the other planets of our solar system where DNA is not likely to be destroyed. In many ways it is an extension of the cosmological principle, and Fred Hoyle was so keen on removing the Earth from any special position in the universe that he never abandoned his Steady state theory because the big bang implies that we live at a special time in the history of the universe. -- Solipsist 19:36, 30 Jul 2004 (UTC)

If we were talking about mere panspermia, then we can agree. I agree that there are differences in what Raelism says and what Crick says. But Crick also talks about DIRECTED panspermia, which hypothesizes that some intelligent civilization INTENTIONALLY spread life throughout the universe. The existence of such intelligent civilzation, though quite plausible, has no proof whatsover. So how are we supposed to accept something scientifically that builds on something that has no scientific proof? I see that the scientific community applies double standards here, one for those inside it (e.g. Crick), and one to the outsiders (e.g. Raelians). I also see a problem with both the the directed panspermia hypothesis, and the Raelian approach (and other Alien Religions), because neither can be tested nor is reproducible to others. If one is not science, then the other is not. We have to be fair. -- KB 15:50, 2004 Aug 8 (UTC)

Yes you are right, there really is little evidence or proof in support of panspermia at the moment - its just an idea. Which is largely why it is a hypothesis rather than a theory and also why most of the scientific community isn't very interested in it. However, panspermia and directed panspermia would have specific consequences about the expected distribution of DNA or amino acids in the solar system and we are getting to the point where we can look for these. The Mars Exploration Rover Mission isn't equipped to look for organic molecules but future missions probably will. Raelism also makes predictions, specifically that once their embassy is constructed, Earth will be visited by extra-terrestrials and they will be about four feet in height. -- Solipsist 08:02, 9 Aug 2004 (UTC)

I'm no expert on Raelism. But from the article on it, it appears to be too intentional to be connected to directed panspermia. Directed panspermia is envisaged a last gasp effort from a civilisation facing extinction. If it is not cost efficient to launch a colonisation attempt, directed panspermia is a strategy to spread DNA in the hope that it will take root somewhere. -- Solipsist 19:01, 30 Jul 2004 (UTC)

I don't think so either. They both involve space and the origins of life on earth, but so do a lot of things. - Omegatron 19:51, Jul 30, 2004 (UTC)

I am now wondering whether we shouldn't have a section making the differences between panspermia and other ideas like Raelism more explicit. -- Solipsist 08:02, 9 Aug 2004 (UTC)

As I noted in the article, the word panspermia is starting to be used colloquially for any origin of life from outer space, which should properly be termed exogenesis. Exogenesis redirects to here, though, so maybe he has a point about the Raelism stuff being related. But only maybe. - Omegatron 01:33, Jan 10, 2005 (UTC)

Evidence and mechanisms

We should also include some "evidence against" bullets. - Omegatron 19:55, Jul 30, 2004 (UTC)

Agreed, but I am not sure there is any yet. As more of a hypothesis than a theory, panspermia is not easily falsifiable. I guess failing to find any evidence of microbial life on Mars, or Europa after extensive searches, would weaken the hypothesis. But that isn't going to happen any time soon. Theories or experiments which bridge the gap between the Urey-Miller experiment and self replicating DNA/RNA might shead new light on the origin of life and invalidate panspermia. -- Solipsist 10:21, 5 Aug 2004 (UTC)

Arrhenius and Panspermia

Astronomer Sir Fred Hoyle and his collaborator N. Chandra Wickramasinghe have built on the modern concept of panspermia set out by the 19th century chemist Svante Arrhenius.

Yes it looks like Arrhenius' theory on spores should be mentioned. This web site (http://www.iscid.org/encyclopedia/Panspermia) suggests several other proponents between Anaxagoras and Hoyle too, with the bibliography to back them up here (http://web.mit.edu/afs/athena.mit.edu/user/r/e/redingtn/www/netadv/bioast/clash/arrhenius.html). -- Solipsist 15:01, 5 Aug 2004 (UTC)

anthropic principle

" (not so unlikely under the anthropic principle), "

are you sure about that? the amount of time original life took to develop really doesn't have any bearing on the eventual existence of humans and wondering about their origins... so if it took dramatically faster than would be expected by chance, that is still a valid observation. - Omegatron 16:02, Dec 23, 2004 (UTC)

Panspermia and Big Splash Theory

Has anyone considered that life came from that Mars like planet that crashed into Earth to form the Moon around 4 billion years ago ?

I dont think its ever been properly explained where that Mars like planet came from. So i suppose its possible to suggest that little green men shot it at just the right angle and velocity to impact earth in just the right way without destroying it, as part of directed Panspermia to create M class planets and seed it with humanoids just like them.

And uh, i think Panspermia is part of the plot in the X files end of season where Mulder was taken.

Ps- if its not already obvious, im not a scientist. Just someone who watches too much tv. *smiles*

Is it widely accepted that Giant impact theory happened? Maybe it was a Generation ship. :-) - Omegatron 18:44, Jan 9, 2005 (UTC)

Yes and no - getting away from X-files speculation and the like, Giant impact theory is fairly credible for the formation of the moon and fits in with the general accretion picture for the formation of the solar system. On the other hand it is the sort of thing which is parallel to, or independent of any theory for the origin of life. Highly energetic events like this can be expected to destroy life if it had already started. Giant impact theory posits that the moon forming impact would have happened during the earliest stages of the formation of the solar system some 4.5 billion years ago. The earlist evidence of life on Earth is several million years after that. Panspermia would suggest that the seeds of life would already be around in the proto-solar system at that time. It may have taken hold on the early Earth, or the Mars size body that impacted it. Life could have be preserved or more likely destroyed, but in any case there would be enough organic material around in the early solar system that it would have reseeded the planets as soon as they had cooled enough for life to take root. -- 22:43, 9 Jan 2005 (UTC)

"e 4.5 billion years ago. The earlist evidence of life on Earth is several million years after that."

I am learning the actual numbers lately, and I think life is supposed to have originated 2 billion ago. - Omegatron 01:33, Jan 10, 2005 (UTC)

Is the data changing on this? Last I heard, the oldest evidence of life on Earth was Stromatolite fossils, dated at about 3.5 billion years old (for example [1] (http://www.ucmp.berkeley.edu/bacteria/cyanofr.html)). -- Solipsist 22:30, 21 Jan 2005 (UTC)

I have no idea. - Omegatron (NOT A GEOLOGY EXPERT. DON'T LISTEN TO HIM.)

Glycine

> In 2002, the discovery of glycine (the simplest amino acid) in interstellar clouds lends additional support.

This reference is in a contradiction with the glycine article, which states that Yi-Jehng Kuan did not made such discovery.

Well actually the glycine article says the Yi-Jehng Kuan result is being contradicted in a yet to be published paper by Lewis Snyder et al. As such it is probably too early to say either way. But if the Yi-Jehng Kuan result is potentially in doubt, the statement should be qualified in this article too. -- Solipsist 22:22, 21 Jan 2005 (UTC)

Faulty Evidence

The glycine bullet was indeed in contradiction with the glycine article. In addition, the ALH84001 bullet was in contradiction with the ALH84001 article and the red rain bullet has been refuted by further scientific investigation. I have edited the page accordingly. Given that these instances of "evidence" for panspermia have been debunked, it might be more appropriate to use them as examples discounting panspermia in the objections section or to at least move them out of the direct evidence category. At present the objections section is pretty weak given that the theory of panspermia is a contentious issue in the scientific community with no true direct evidence. I would suggest that contributers do more thorough fact checking before making posts on issues of this sort. Wikipedia does not need to be labeled as a host to pseudoscience. I find the cryptozoology articles much more balanced in this respect. -- Mark 20:58, 27 Feb 2005 (UTC)

Thanks for fixing it. That's the whole point. - Omegatron 04:48, Feb 28, 2005 (UTC)

A Touch Optimistic?

(Original talk page comments in bold italics)

I think this article needs to be a lot more skeptical regarding the issues at hand. The evidence isn't really evidence: the conditions that allow for panspmeria are described, but it's actually having occured on Earth is nowhere supported. It isn't emphasized that panspmeria is quite a minority opinion and objections to the idea are not seriously raised. Marskell

We should also include some "evidence against" bullets. - Omegatron 19:55, Jul 30, 2004 (UTC)

Agreed, but I am not sure there is any yet. As more of a hypothesis than a theory, panspermia is not easily falsifiable.

The most obvious evidence against is the enormous time it requires for ejecta from bodies outside the solar system to reach Earth and the extremely slim chance of any micro-biotic criters surviving. Imagine a comet flying in from Alpha Centauri at 1% light speed (a generous estimate): 400 hundred plus years to get here and then, of course, the body must find it's way to Earth and anything still alive must survive Earth-entry and subsequently propogate. Marskell

If circumstantial evidence that allows panspermia "isn't really evidence", then your evidence that disallows it isn't really evidence, either. Besides, these things are addressed in the article. - Omegatron 18:35, Apr 11, 2005 (UTC)

A second objection is based on Occam's Razor, which states that when multiple explanations are available for a phenomenon, the simplest version is preferred. It is not so clear that geogenesis is to be preferred over exogenesis under this rule.

Really?! I’ll assume I was born of the woman who raised me until I find evidence to the contrary! ;) Marskell

I don't see how this is a good analogy. - Omegatron 18:35, Apr 11, 2005 (UTC)

The former eliminates the step of transferring life across space, but requires a lot to happen in a relatively short time frame. If that short time frame is typical and not an aberration, life in general (including intelligent life) should be common in the universe, raising the Fermi paradox: Where are they?

First, as a matter of basic common sense Occam’s Razor dictates geogensis ahead of exogensis. The latter requires two steps: origin off Earth and subsequent transmission, while the former requires only one—in a short time fine, but 700 million to 1 billion years is longer, even in geologic terms, than this article makes out (about 5% of the universe’s overall age, which ain’t bad).

Secondly, panspmeria and exogensis foreground Fermi’s Paradox more strongly than geogensis. If Earth-life was seeded off Earth, after all, we should expect to find quite a lot of extraterrestrial activity. Marskell 17:47, 11 Apr 2005 (UTC)

How would we measure this activity? - Omegatron 18:35, Apr 11, 2005 (UTC)

I'm not sure it is worth arguing the points individually, but Marskell's basic comment that the article doesn't make it clear that Pansermia is _not_ a mainstream theory is valid. In reality, Panspermia is an interesting idea that is waiting in the wings for more corroborating evidence. Its stock would rise significantly if evidence of life was found somewhere else in the solar system, or (less likely) if hard limits were placed on the spontaneous creation of life which made it very unlikely to have first occured on Earth.

It would be worth updating the opening para to make this clear. -- Solipsist 19:36, 11 Apr 2005 (UTC)

Late Heavy Bombardment

I've changed this section somewhat.

• It is very unlikely the Earth was not affected to a similar or greater extent to the Moon, as they are very close and the Earth's greater gravitational field would likely attract more impactors. Also there is further evidence that the event was felt throughout the inner Solar System (Kring & Cohen 2002, although I could get hold of the full article).

• The likelihood is that the LHB was so intense that the surface was sterilised. Cohen (2000) suggests 100x impact rate. The situation for hydrothermal vents is not so clear cut, but possible these were sterilised too. If not, this may expand the window for a hydrothermal origin.

The upshot is a much shorter window for life to emerge. I've noted several alternatives, the upper of which is really rock-solid (formation of earth => first stromatolites). The Isua 13-C signal is under doubt because the rocks have been metamorphosed, and the signal is somewhat different to later rocks.

I'm not sure though that you can really count this as an argument - even circumstantial - for exogenesis when we know so little of the mechanisms behind the emergence of life. Maybe life doesn't take very long to emerge in the right conditions, and even 100Ma is plenty. If we *knew* that life took a long time to emerge, then the short time frame would be circumstantial evidence for exogenesis, but as we don't - does it really tell us anything? I suggest this entire section (i.e. narrow time window for geogenesis) go into Origin of Life as it is really more relevant there. It could still be mentioned here as a tenuously circumstantial pointer to exogenesis. What do you think?

Tonderai 16:48, 15 Apr 2005 (UTC)

I don't think you want to move timing arguments out of this page. As I understand it, whether it is relevant or not, the rapid appearance of life on Earth was one of the main impulses behind speculating about Panspermia. It is true, that Panspermia conjectures that the spontaneous creation of life is difficult and therefore rare. However this is a big unknown. The gap between the Miller-Urey experiment producing amino-acids and the development of RNA is a big chasm. But in time theoretical molecular biology might show that it is a chasm that is easy to cross. If so then the spontaneous creation of life is easy and Panspermia become largely irrelevant.

If it turns out that the chasm is difficult to cross, yet the evidence for primordial life is common throughout the solar system, then Panspermia becomes plausible. Conversely, if Earth is the only planet to show evidence of life, then Panspermia is largely invalidated.

The fact that life appears on Earth very shortly after it become possible to support it, is surprising. It suggests that either life is easy to get going, or something like Panspermia seeds every planet that is physically able to support life. -- Solipsist 20:53, 15 Apr 2005 (UTC)

You are right that amino-acids to life seems a huge chasm especially when you don't know how it happened. And it becomes even more surprising if you accept the LHB as a steriliser and the Isua C-13 fractionation - only 100Ma possibly! This seems a very short period of time for life to emerge, especially considering the several billion years before multicellular organsisms appeared. So you're right, a shorter window makes exogenesis more plausible unless we can show the process can happen very rapidly.

I think we await more evidence here, when you are dealing with plausibilities almost anything can go :)

Tonderai 22:23, Apr 15, 2005 (UTC)

This idea definitely needs a lot more evidence and is depends on a lot of unknowns, just like the origin of life. It should be presented as such, but shouldn't be dismissed or have parts removed because of this. - Omegatron 23:51, Apr 15, 2005 (UTC)

Direct Evidence of Extraterrestrial Life

There is as yet no definitive direct evidence of extraterrestrial life - this should be made clear.

• Two of the Viking biology experiments gave positive results. However the third showed there were no organic molecules in the Martian soil (organic molecules are widespread in similar terrestrial environments such as Antarctica). Subsequent experiments showed that the other two 'positives' could be reproduced using terrestrial clays. The results are generally accepted as being abiotically produced. To say 'official NASA stance' is rather conspiracy-theory-esque, in fact this is the general scientific consensus.

• Red rain point should be removed if it has been debunked.

• High altitude bacteria may show mixing from lower atmosphere or from space, but either supports panspermia as it shows either bacteria are present in space or can leave the lower atmosphere from Earth towards space. Keep this.

• Although the Glycine claim has been debunked, there are indeed a wide variety of organic molecules in interstellar space. This is significant for prebiotic chemistry, but not so for panspermia which requires viable lifeforms that are distinct from simple organics such as amino acids.

Btw thanks Omegatron for the spelling corrections! Tonderai 22:57, Apr 18, 2005 (UTC)

Changes

The introductory changes are very good--it reads much more critically now.

Omegatron, you're right to underscore my speculating after criticizing the article for being too speculative! I only used the example of a body coming from Alpha Centauri to put things in perspective. Life coming from Mars to Earth or vice versa could "hang-on" for the journey, but coming from another solar system (with a minimum window of a few centuries) it would need to reproduce and remain viable on the meteor itself. In terms of time frames a more realistic example is the voyager probes. Voyager 2 (still humming along at 3+ AU/year) will take 300 000 years to reach the neighbourhood of Sirius!

As for my analogy to motherhood I think you get the point: if I'm speculating about origins I'll assume the obvious unless other evidence jumps out at me. Marskell 04:06, 20 Apr 2005 (UTC)