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Astrobiologists Find Ancient Fossils in Meteorite Fragments (technologyreview.com)
252 points by uptown on Mar 11, 2013 | hide | past | web | favorite | 86 comments

"This is an idea put forward by Fred Hoyle and Chandra Wickramasinghe, the latter being a member of the team who has carried out this analysis."

Chandra Wickramasinghe is currently the MAIN guy promoting the idea discussed in the article kindly submitted here (as Hoyle has died). Hacker News participants can gain perspective on this idea by reading "Diatoms…iiiiin spaaaaaaaaaaace!"



"Chandra Wickramasinghe replies…and fails hard"


to see comments by a biologist on why the evidence here is completely inadequate for Wickramasinghe's latest claim. Wickramasinghe has been around the block with claims like this before, and he is the editor of the main "journal" that promotes this idea, but none of his specific claims of finding extraterrestrial life have ever been backed up by convincing evidence.

EDIT: I should add the link to a critique of the extraordinary claim here by an astronomer


(this was linked in the links I put in this comment earlier), so you can see his comments on the new claim directly.

While there seem to be serious issues with the research, it's hard to be won over by an article that starts with "You all know that the Journal of Cosmology is complete crap, right? In addition to some of the worst web design ever — it looks like a drunk clown puked up his fruit loops onto a grid of 1990s-style tables — the content is ridiculous, predictable, and credulous," and continues with "That’s the kind of rigorous scientific thinking we’re dealing with here." Admittedly I've never liked Myers style since he always has seemed to be an obnoxious advocate of a certain brand of orthodoxy, rather than giving any sense of nuanced or rigorous (scientific or otherwise) thinking.

You leave out the part where the Journal of Cosmology photoshopped Myers' head onto a picture of a plump woman in negligee.

By their fruits you shall know them. Sometimes it's appropriate to use a heavy touch. I would agree Myers relies on it much too much, but it's not inherently bad.

Though, as a minor point, Myers' site itself could use some better design chops...

>rather than giving any sense of nuanced or rigorous (scientific or otherwise) thinking.

Have you read his blog posts that aren't about atheism, or debunking, but are just about what he researches and teaches? Here's an example from today: http://scienceblogs.com/pharyngula/2013/03/11/what-i-taught-...

Especially since I know many solid scientific websites with horrible design (especially professors' personal sites), so it's almost a show of ignorance to try and connect "rigorous scientific thinking" with proper web design.

Personal websites, yes. Academic journals tend to look professional - which doesn't always mean great web design, but it definitely doesn't mean what you see at journalofcosmology.com. If you had solid evidence for the biggest biological claim of the century, you'd take it to the top journals - Nature or Science.

You're right, so it's good that Myers wasn't anywhere close to connecting those things, which you'd know if you read the blog post.

Some things are so obviously bullshit, they deserve no serious treatment. This is one of them.

The identified structures look no more nor less "lifelike" than other random bits found in the rock (image is here [1]).

As far as I can tell, this evidence doesn't even begin to scratch at the surface of information needed to demonstrate or even really suggest that these were ever living organisms.

The nail in the coffin, for me, is the fact that this is set to be published in the Journal of Cosmology, a publication of questionable repute [2].

[1] https://www.technologyreview.com/sites/default/files/images/...

[2] https://en.wikipedia.org/wiki/Journal_of_Cosmology

Absolutely. It would be great it was true, but it's almost certainly not.

Images like this are effectively Rorschach tests. Sure, they may look like xenofossils to astrobiologists, but there are no doubt people to whom they look like their grandmother lying in a pool of blood...

It would be great it was true

Extraterrestrial life would be great? I'm not sure. I think the 2 most likely scenarios are: 1. ET would be far less evolved 2. ET would be far more evolved

#1 wouldn't be terribly interesting. So what about #2. What would that be like?

Well, we have some relevant experience from planet earth.

How do humans view/treat organisms that are far less evolved ... like bugs?

How do humans view/treat organisms that are far less evolved ... like bugs?

Any time someone says something like this, that's proof that they don't actually understand evolution.

Bugs have been evolving for exactly as long as we have. Bugs outnumber us, outweigh us, and there are ridiculously more types of them than there are of all kinds of vertebrate life.

We have been able to achieve an undue impact on our environment. But bugs are not less evolved than we are.

Let me add to the surprises. Most fish are evolved from air breathing animals. Our eyes contain a trivial design mistakes that an octopus does not. And we are more closely related to a goldfish than either is to a shark.

If any of this comes as a surprise, then you have confirmed my comment that you don't actually understand evolution.

Edit: Originally I said "land-dwelling" instead of "air-breathing". I do not know of direct evidence about land dwelling, however the swim bladder is believed to be evolved from a lung.

>Bugs have been evolving for exactly as long as we have.

Even more importantly, bugs have been through many more generations than we have. If anything it is the bugs that are "more evolved".

It turns out that evolutionary change doesn't so much depend on how many generations there have been (because things tend to be well enough adapted to their environment that obvious changes don't help much), but rather on how much their environment has changed around them.

That said, the amazing diversity of beetles suggests that some types of bugs have indeed been changing rapidly.

Of course. Number of generations is merely one step less irrelevant than the amount of time that has passed.

As with most things there is a nearly tower of progressively more accurate statements that could be made.

I think it may be more accurate to say, life has been evolving for the same amount of time. Since bugs predate anything even resembling a human by a colossal amount of millennia.

I feel you have been given some misinformation. Most aquatic mammals evolved from land based mammals, but the fishes have been evolving from fishes for as long as we have a fossil record for. The Osteichthyes or bony fished (Tuna, Salmon) evolved from Chondrichthyes cartilaginous fishes(Sharks, Rays), but none of these evolved from land based animals.

See edit.

I believe you still have that backwards.

Most fish are evolved from land-dwelling animals

I wanted to check your source for this proposition, because after I upvoted your comment on other grounds, I wasn't completely sure that this squares with what I have read about evolution.

For example, this link


is to the contrary, suggesting that most fish living today had ancestors that were aquatic.

AFTER EDIT: To acknowledge your kind reply, I wondered if that was what you were getting at. To me, "land dwelling" implies, among other key behaviors, breeding and laying eggs on land. By contrast, "air breathing" would be a term unambiguous for what you meant, and still surprising to most readers.

The swim bladder is a modified lung: http://en.wikipedia.org/wiki/Swim_bladder#Evolution

Wikipedia claims that this is thought to have evolved as a survival method in oxygen poor water. My understanding had been that this was because their ancestors, however briefly, were adapted to survive out of the water. If only as well as today's lungfish.

My understanding may be wrong. But still, most fishes today are descended from air-breathing ancestors.

I think you're nitpicking. The good kind (good information in there) but still nitting. Developed, intellectually, culturally and so on is clearly what he meant.

Reading the wiki link, it looks like sharks do not have this feature since there was a divergence prior to this. What this says to me is they probably were water dwelling but for some reason developed lungs (a short stint on land and went on to find their true calling in the water)? Or they could have started out mostly in shallow water or spent a lot of time near the surface.

>>>> EDIT More searching suggests that the picture is quite murky.

The swim bladder and lungs of aquatic and terrestrial organisms arose independently from a common primordial “respiratory pharynx” but not from each other...If there is commonality among these diverse respiratory processes, it is that all levels of organization, from molecular signaling to structure to function, co-evolve progressively, and optimize an existing gas-exchange framework.



Also, surprise is trivially true given unknown data even if it properly fits one's model since no one follows all deductions of a model to generate all data. Plus, the brain tends to compartmentalize.

And if he would like an overview of evolution An Ancestor's Tale would be a great book to pickup. www.amazon.com/gp/aw/d/061861916X/ref=redir_mdp_mobile/185-0865240-1556308

Any time someone says something like this, that's proof that they don't actually understand evolution.

I won't be snarky. I'll just point out that evolution has multiple meanings and I think that it's obvious from context that in this case I'm using 'evolved' as shorthand for more intelligent/advanced/sophisticated.

> I'll just point out that evolution has multiple meanings and I think that it's obvious from context that in this case I'm using 'evolved' as shorthand for more intelligent/advanced/sophisticated.

Yes, but that's not what evolution means. Natural selection chooses the fittest genotype, not the "more advanced". The idea that evolution progresses from simple to complex is a myth -- a persistent myth, but a myth nevertheless.

Evolution isn't a program with a specific outcome, it's a blind algorithm that chooses the fittest genotype at every turn. If the "fittest" genotype is a cockroach, for example after a nuclear war, that's the outcome. Evolution doesn't care about our tastes because nature doesn't care about our tastes.

that's not what evolution means.

Biological evolution is only one of many meanings of the word evolution. (I promise, I'm aware that bugs have been biologically evolving for longer than humans.)


1. any process of formation or growth; development: the evolution of a language; the evolution of the airplane.

2.a product of such development; something evolved: The exploration of space is the evolution of decades of research.

3.Biology . change in the gene pool of a population from generation to generation by such processes as mutation, natural selection, and genetic drift.

4. a process of gradual, peaceful, progressive change or development, as in social or economic structure or institutions.

5.a motion incomplete in itself, but combining with coordinated motions to produce a single action, as in a machine.

Just do a google search for 'spiritually evolved', 'evolved beings', 'evolved man' ... you'll see what I mean.

as I said, thought it was clear from context.

Whoa, hold on, In a technical or scientific discussion, you don't want to rely on a dictionary. Dictionaries, contrary to common belief, do not define words -- instead, they dispassionately describe how people choose to use words. If a word use makes no sense, that doesn't matter as long as the use is widespread. This is why "literally" and "figuratively" are ... wait for it ... synonyms.


1. : in a literal sense or manner : actually <took the remark literally> <was literally insane>

2. : in effect : virtually <will literally turn the world upside down to combat cruelty or injustice — Norman Cousins>

Read more here: http://arachnoid.com/wrong/index.html#Dictionary

> ... as I said, thought it was clear from context.

Not in any kind of serious discussion, with pretensions of accuracy.

it never occurred to me that a discussion on an internet bulletin board about whether space aliens are likely to be hostile was a 'technical or scientific discussion'.

Yes, but it did establish a context for use of the word "evolution" -- the biological one.

Isn't that exactly the problem? The relationship between intelligence and duration-of-evolution is not direct and linear.

In response to your assertion, it seems to me that with our advances in medicine it doesn't look likely that we're going to evolve greater intelligence. I would expect any species that evolves our level of intelligence will take an interest in medicine and arrive at basically the same steady state. So I'm going to make a completely unsupportable and useless from-first-principles prediction that intelligent life elsewhere in the cosmos will be approximately as intelligent as us.

The belief that humans have arrived at a plateau and no longer are subject to evolution is also evidence that you do not understand evolution.

I assure you, homo sapiens is under great evolutionary pressure to evolve an effective response to birth control.

It is also worth noting that it is suspected that our large brains mostly reached their present size to enable us to be more effective in interacting with each other. As long as we would prefer to not wind up alone on Saturday night, we'll be under pressure to better figure out how to get other humans to do what we want them to do. There is no upper limit to how much intelligence could be brought to bear on that problem.

(Though in practice I believe that we'll build machines smarter than us, which will improve far more rapidly than we could ever hope to.)

So, your counterargument is that birth control and Saturday Night Fever will have a bigger effect on the evolutionary process than enabling people with congenital diseases to reproduce, and that, moreover, this will somehow continue to produce increases in intelligence at the same rate as we experienced going from ape to human?

I'm not claiming evolution is finished. I'm claiming it is affected and I don't see compelling pressure to select for ever-greater intelligence. Even if I found your argument compelling, you're hardly talking about the same kind of intelligence as the GP. Intelligence is one of those squishy things that resists good formal definition.

I am not trying to predict the future. I am merely saying that evolution isn't done, and the presence of medicine and a high quality of life doesn't change the basic equation of "survival of the fittest".

And intelligence is selected for for reasons that are not addressed by modern medicine.

"design mistake"

there is no design[er]

Down voted for this??? I thought the hn community was smarte than that. Hands up then that disagrees with the scientific community??? Ok, now please leave this forum. Or at least prefix your username with something like creationist_<user> so I can know whom to ignore :) wake up, it's the 21st century, the era of superstition and myth has passed and unless we want to return to the dark ages we need to foster forward thinking philosophies and not mire ourselves in the flat earth era of thinking.

Comparing amounts of evolution isn't really valid. This implies that evolution has a directional trend, but it does not. Humanity wasn't the goal of evolution. Given a different climate 10 or 15 thousand year ago, things could have been a lot different. Neanderthals could have won out, or both our species could have gone extinct.

I think a better, and similar, comparison would be of intelligence. We treat less intelligent animals quite poorly for the most part. Hopefully the correlation between empathy and intelligence is universal and not just a trend among humans.

> Hopefully the correlation between empathy and intelligence is universal and not just a trend among humans.

I hate to rain on your parade, but empathy and intelligence are selected only insofar as it supports survival and procreation -- only to the degree that it supports natural selection.

Empathy and intelligence are just neutral terms in a complex equation by which natural selection chooses the fittest genotype. They have no special standing, and a fair reading of human and natural history shows that, overall, they're not correlated with the survival of the species that possesses it.

Evidence? Count the number, or the biomass if you prefer, of the species that survive in a brainless, ruthless manner. Compare to those whose fitness is enhanced by empathy and intelligence. And remember that overall we can't be included in the intelligent, empathic column, at least not when we're doing our best to survive.

The best-informed speculation of today says that within the last 150,000 years (different methods give different dates, the Toba supervolcano is often fingered as a culprit) we went through a population bottleneck with as few as a thousand people alive.

This evolutionary episode would have been a period of rapid adaptation, and amusingly is suspected to have been when our ancestors acquired a tendency towards religious belief. (We are the only known hominid with things like burial rites.)

You are assuming that a highly evolved lifeform would act like us humans, barely out of the trees socially and spiritually. You may be right. However there are many people I know that wouldn't hurt a bug.

Tangentially, #1 would be incredibly interesting to many people. We (the general public) have no definite indications that we /aren't/ on the only rock in the Universe with life, and #1 would hold great consequences.

Agreed, #1 would still be earth-shaking. At the moment, we're the only life we know of. Finding evidence of extraterrestial microbes in the same solar system would suggest a much higher probability for life all over the galaxy.

> #1 wouldn't be terribly interesting.

The scary implication of #1 is that it updates our probability for long-term survival and becoming a technologically advanced, space-faring species: by _lowering_ it. That's because it pushes the potential Great Filter [1] closer to our present condition and increasing the odds that it's actually somewhere in our future.

[1] http://en.wikipedia.org/wiki/Great_filter

Though, statistically, if you push the "the great filter" closer to our present condition, don't you actually push the bulk of the probable filter events to before our present condition, events which are evidently not true in our case, and actually _raise_ our probability of long-term survival?

Remember that you still need to explain the Fermi paradox [1]. If you apply the above logic to life & civilizations in general, you conclude that it's actually quite likely for them to survive long enough and become widespread. Yet, our experience contradicts that assertion, for we don't know any other race at even comparable level of technical development

Of course, this (i.e. civilization quickly become extinct) is just one possible resolution to the paradox, but the arguably simplest one. If the actual reason(s) we don't see advanced life are different, the Great filter hypothesis holds less water. We don't know that yet, though.

[1] http://en.wikipedia.org/wiki/Fermi_paradox

I've always thought the fact that the vast open spaces in the universe is really quite sufficient to explain the fermi paradox

I don't know. We actually seem to have a pretty strong affinity for other forms of life. I can't imagine any other animal on earth preserving dumber animals they could potentially eat. We like other animals - especially those with faces and discernible intelligence.

Now you might say that this is irrelevant. Just because we like other animals doesn't mean the aliens will. This is a good point, except that it completely invalidates the premise put forth of "experience from planet earth."

I have to believe that any organism sophisticated enough to find us would be amazed. They may be far more advanced, but seeing the lifelessness of space and the complexity of our civilization, anything with a shred of intelligence would be at least intrigued. Speculating on their nature and disposition is meaningless and arbitrary at this point.

Bugs are going to eat us all, one day.

My whole family was in Buenos Aires

I don't think many will get this reference to Starship Troopers, a rather good film in spite of its reliance on endless gore.

A good book also, despite its senselessly piled on militarism. Strangely quite the opposite of the film in that regard.

"The nail in the coffin, for me, is the fact that this is set to be published in the Journal of Cosmology, a publication of questionable repute [2]."

So it's ok to go Ad Hominem against anything that contradicts our current knowledge? Ok, got it

No, it's that an extraordinary claim that would revolutionize our understanding of the universe would be likely to be published in a high-impact journal, if it is backed up by enough evidence to survive review in that journal. When the principal investigator of a study is someone who has to publish in his own journal,


(Wickramasinghe is "Executive Editor, Astrobiology" for the Journal of Cosmology)

then you can see for yourself a bad sign about the strength of evidence for the paper.



for more details on identifying reliable sources.


The group blog Retraction Watch


is an excellent glimpse into the world of scientific publishing, and shows how many low-ranking journals there are that are hard up for content. I think I learned about this interesting blog from another HN participant a year or two ago.

The article should stand (or not) on its merits, regardless of the journal of publication (or other medium)

Of course I trust Nature more than, let's say "Bob's Journal about science stuff"

But sometimes even articles in Nature have been printed elsewhere first, (like a 'beta test' for the article - peer review nevertheless), usually in journals specific from the field (clarification below)

The "Identifying reliable sources" page is a Wikipedia policy, it has some good insights, but it is biased towards Wikipedia, see for example "Articles should rely on secondary sources whenever possible. For example, a review article, monograph, or textbook is better than a primary research paper"

Edit: Yes, journals usually don't accept content published elsewhere, my bad.

What happens is that, yes, you can't republish something 100% equal to something published elsewhere. (eg: http://www.ieee.org/documents/top10faq.pdf ) but while the research progresses you provide more detailed papers or focus on different areas of research

> But sometimes even articles in Nature have been printed elsewhere first, (like a 'beta test' for the article - peer review nevertheless), usually in journals specific from the field.

Not true. Republishing already-published work is specifically disallowed by Nature and most high impact journals. Doing so merits a retraction.

> So it's ok to go Ad Hominem against anything that contradicts our current knowledge? Ok, got it

The whole point of scientific journals is to change our current knowledge, so that's not really a fair criticism of my dismissal.

Read even just the Wikipedia article and you'll see that this journal has several issues: (1) the quality of its peer review is questionable; (2) it appears to promote fringe views; (3) it has been widely criticized by the scientific community.

So yes, after criticizing the research itself, I also dug around and discovered problems with the journal it was being published in. I don't see anything wrong with doing so. Had the data looked less bogus I probably wouldn't have been suspicious enough to investigate the source.

"So yes, after criticizing the research itself"

Your point was that these features look as similar as other features and hence they should be the same.

Now, the given article really reads like a press release more than anything, but I don't remember if the original article had something else on the picture.

What I would think is that (but I am not sure) since these are electron microscope pictures, you can get a composition analysis of the sample from the microscope, hence being able to differentiate the features.

And no, I'm not taking this research too seriously as well, I just find it funny that some people jump at it and seem to dismiss it at first sight.

Their previous paper[1], and will only take about five to ten minutes to read, and gives you a pretty good idea what the level of this "journal" is.

Phil Plaitt also has a pretty good critique[2], but if you have the background, reading that paper should be enough to at least make you squint hard at their "science". There's a reason that people don't take the group seriously, and it's not fear from the establishment or whatever nonsense.

[1] http://journalofcosmology.com/JOC21/PolonnaruwaRRRR.pdf

[2] http://www.slate.com/blogs/bad_astronomy/2013/01/15/life_in_...

It's not an ad hominem to suggest that a piece of unconventional research is unlikely to be correct because it is published in a disreputable journal. Academia is all about reputation, and the standing of various journals.

If they had sufficient evidence to back up their claims then they would be on the cover of Nature. Unfortunately for them, actual Science requires peer-reviewed evidence. Publishing in your own journal does not count. It's a huge red flag.

If you are not an expert in the field, it will be very hard if not impossible for you to judge a scientific article on its merits.

In that light, looking at where something was published makes total sense. It’s a completely valid mechanism for non-experts to separate the crap from the good stuff. (Even experts, given all the stuff that is published all the time, have no time to read and evaluate everything on its merits. Increasing efficiency by centralizing that task and not forcing every scientist to do it all the time is more or less the purpose of journals.)

No, that's only a comment on the care taken with the norms of scientific discipline. Anyone can get an astrology paper published, just not in a reputable, refereed journal.

It doesn't have the same reputation as New Scientist, but I'm taking it with some cautious optimism. I'm still reading the original report to filter through any embellishments etc... While structures alone may not provide conclusive evidence, perhaps the composition will.

The name Anil Samaranayake caught my eye, since he's the the director of the Colombo Medical Research Institute.

> published in the Journal of Cosmology, a publication of questionable repute [2].

Well, at least their publications are not behind a paywall, free for download:


so anyone can check the believability of this research themselves!

I think the biggest thing for me is that it hasn't been verified by multiple studies... I tend to look for a broader acceptance than in one place. Then it's really a debate, this is just a cool finding that needs to be peer reviewed.

So I'd say it's too early to pull out the nails or the coffin, it is just an unverified theory right now. Those are a dime a dozen.

There are some serious problems with this claim:

1. "In total, Jamie Wallis at Cardiff University and a few buddies received 628 stone fragments collected from rice fields in the region. However, they were able to clearly identify only three as possible meteorites."

In other words, the researchers weren't in on the collection activity, and may not possess the expertise to distinguish meteoritic material from ordinary earthly rocks (that determination is not easy).

2. "One stone, for example, had a density of less than 1 gram per cubic centimetre, less than all known carbonaceous meteorites."

And it didn't occur to these people that it wasn't a meteorite? Low-density meteors don't normally get to the ground -- they are much more likely to vaporize in the atmosphere. A low-density sample like this is immediately suspect.

Conclusion: Three identifications out of 628 samples, one of the three is not likely to be a real meteorite, terrestrial contamination cannot really be ruled out, and this work is neither refereed AFAIK nor published in a normal scientific journal. I call shenanigans.

Reference: http://arxiv.org/abs/1303.1845

This has come up before. Although this paper is considerably better presented than the previous one, the conclusions are still the same - the author is biased and the evidence is weak.



Previously: http://news.ycombinator.com/item?id=5055227

General HN comment consensus is that the article is terribly poor science, published in a crank journal.

Note: It was about a different analysis of the same event, by almost the same authors.

Its probably worth reading the last two paragraphs first:

"There are other explanations, of course. One is that the fireball was of terrestrial origin, a remnant of one of the many asteroid impacts in Earth’s history that that have ejected billions of tonnes of rock and water into space, presumably with biological material inside. Another is that the structures are not biological and have a different explanation.

Either way, considerably more work will have to be done before the claims from this team can be broadly accepted. Exciting times ahead!"

Please, please stop voting pseudo-science up so much. Look at the comments in the post. The second one pretty much explains why this "paper" has no credibility what-so-ever.

Been there, done that:


From the wiki article: '[T]he scientific consensus is that "morphology alone cannot be used unambiguously as a tool for primitive life detection."'

But let me know when they find a skeleton fossil in a meteorite.

Why is this article receiving so many upvotes given the rather apparent consensus that it is overhyped and/or untrustworthy analysis presented in a disreputable journal?

It's curious the MIT article tries to downplay the role of Wickramasinghe behind this research finding. NC Wickramasinghe may be a brilliant scientist, but any news regarding possible extra-terrestrial life-form and his name appearing together instantly raises alarm bells all over the place. Wickramasinghe is the von Däniken of astrobiology.

Let's all keep in mind that this paper was published by physicists, in non-peer reviewed journals.

There is a lot of jumping the gun in these articles, especially when it's the lead authors first and only paper. Here is a link to the actual paper:


Here is a slate article that has already proven that the data mined by the "Astrobiologists" is faulty and biased:


I wouldn't call this clear evidence. Is it not possible the a large asteroid struck earth, kicking up debri from earth which happened to contain micro organisms. These organisms then died and fossilized in the space later returning...

Could they not carbon date the fossils to see if they correspond with the existence of similar lifeforms on Earth?

I do not think this would work on organisms that did not live and die in our atmosphere because the ratio of C12 and C14 is local to our atmosphere and might be very different where they come from.

Carbon dating is only good for about 50,000 years back. There are other radiometric dating methods, but none as useful for dating lifeforms.

that apparently wouldn't work on extra-terrestrial stuff as it seems to depend on "the ratio of 14C to 12C in the atmosphere" and works for "up to about 58,000 to 62,000 years"[1]

[1] http://en.wikipedia.org/wiki/Radiocarbon_dating

Right, so if it turned out to come from the future or 10 billion years ago on that scale, then it's likely extraterrestrial.

As you say though, it's not good in the billions.

You're not getting it. You can't date anything non-biological using carbon dating. It's not that you get the wrong answer. You get no answer, since you don't know a-priori what the ratio of C12 to C14 was when the sample was formed. The equations are under-constrained.

You can still use radiological dating with other elements (e.g. Uranium).

>if it turned out to come from the future

I don't even…

Difficult to get what was not said in the comment I'm replying to. So fine, I don't know my dating techniques. Uranium radiological dating sounds fine. Why not that?

>> if it turned out to come from the future

> I don't even…

have a sense of humor? It is certainly possible if we had a extra-terrestrial organic matter (which we don't) that it could test as coming from the future based on carbon ratios, though obviously it would not actually be from the future - thus "on that scale".

I'm not sure if the same applies to Uranium radiological dating.

But we don't know future carbon ratios.

"Extraordinary claims require extraordinary evidence" - Carl Sagan

When you find a fossilised rabbit in the meteorite, call me.

Why does it always have to be Cardiff that gets all the aliens?

Their city is built on a rift in the time space continuom. The energy it gives off can be harnessed to recharge the TARDIS.

It seems questionable but...

Even if it was true, couldn't it have been organisms from earth ejected into orbit after a meteor strike and, thousands of years later or more, falling back to earth?

Now if we find a definitive proof of panspermia it would be the biggest discovery ever made by mankind so far...

>couldn't it have been organisms from earth ejected into orbit after a meteor strike and, thousands of years later or more, falling back to earth?

That would still be a hugely significant result.

We expect a higher density of biologically contaminated samples near the Earth. This is perfectly compatible with (but does not prove) panspermia.

The key question isn't whether space is sterile, but whether space is aseptic. That's harder to demonstrate.

To illustrate the difference, imagine a doctor scrubbing for surgery. It's impossible to scrub your hands until there's a population of zero pathogens, but fortunately that is unnecessary. You just need to reduce the population enough that the few organisms that remain just can't get a foot-hold.

We're in the back waters of the galaxy in a mature star system. Even if panspermia were rampant in the galaxy, we probably wouldn't see it. Stellar clusters, nebulae, Bok globules, and young star systems are where you would expect this kind of action.

Mechanically speaking panspemia is just diffusion, except instead of Brownian motion you have impact ejecta and gravitational evaporation. Each of these events has a probability curve. You could even construct your own "Panspermia Drake Equation", something like:

  P  = N_seed * R_ejection * Pop_specific * f_survival_ejection * f_escape
     * 2^-(T_encounter / t_1/2_cruise)
     * f_habitable * f_survival_reentry * f_germination
  P =                  rate of panspermia in a given volume of space
  N_seed =             number of seed (life-bearing) bodies in that volume
  R_ejection =         average rate at which mass is ejected from each
                         seed body (kg/yr)
  Pop_specific =       average specific population ('von Neumann'
                         individuals/kg) of ejected material
  f_survive_ejection = fraction of population that survives ejection
  f_escape =           fraction of ejected material that eventually escapes from
                         the stellar system, either due to initial velocity
                         or long-term orbital perturbations
  T_encounter =        average length of time before an escaped
                         object encounters another body
  t_1/2_cruise =       half-life of population exposed to interstellar conditions
  f_habitable =        fraction of encountered bodies that are habitable
  f_survive_reentry =  fraction of population that survives reentry
  f_germination =      fraction of the population that actually germinates
Looking at this equation it's not hard to see why dense regions with young star systems are preferred. Young systems have higher ejection and escape rates. Survival rates for ejection and re-entry are a function of energy, so having many less massive bodies is preferred. Young, single-cell-only ecosystems increase the specific population.

Of course, The number of seed bodies (N_seed) is the interesting part. This allows the equation to feed back on itself. Waaaaaaay out here in the Solar neighborhood, everything's so far apart that T_encounter rate limits that feedback to effectively zero, but in stellar clusters and nebulae you can find regions with dozens of stars per cubic light-year. As stars move within the galaxy they might experience different rates of panspermia – perhaps long lifeless intervals punctuated by "bursts" of bombardment, or maybe just once (in the conditions of the stellar nursery) and then never again.

When it comes to panspermia as an origin theory (aka exogenesis) I consider myself a "weak atheist", if you will. The meager evidence we have seems to suggest that life on Earth originated in abiogenesis, not panspermia. That doesn't mean that panspermia does not occur.

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