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STARS MOVE! STARS MOVE! STARS MOVE!
james_nicoll
Transfer of Life-Bearing Meteorites from Earth to Other Planets
Tetsuya Hara, Kazuma Takagi, Daigo Kajiura
(Submitted on 8 Apr 2012)

The probability is investigated that the meteorites originating on Earth are transferred to other planets in our Solar System and to extra solar planets.
We take the collisional Chicxulub crater event, and material that was ejected as an example of Earth-origin meteors.
If we assume the appropriate size of the meteorites as 1cm in diameter, the number of meteorites to reach the exoplanet system (further than 20 ly) would be much greater than one. We have followed the ejection and capture rates estimated by Melosh (2003) and the discussion by Wallis and Wickramasinghe (2004). If we consider the possibility that the fragmented ejecta (smaller than 1cm) are accreted to comets and other icy bodies, then buried fertile material could make the interstellar journey throughout Galaxy. If life forms inside remain viable, this would be evidence of life from Earth seeding other planets.
We also estimate the transfer velocity of the micro-organisms in the interstellar space. In some assumptions, it could be estimated that, if life has originated $10^{10}$\ years ago anywhere in our Galaxy as theorized by Joseph and Schild (2010a, b), it will have since propagated throughout our Galaxy and could have arrived on Earth by 4.6 billion years ago. Organisms disperse.


I am not sure how many $10^{10}$\ is as I am unfamiliar with the $\ system of measuring stuff.

Dear authors of this paper and in particular this sentence:

"As the distance to Gl 581 is 20 light years,"

Not 65 million years ago it wasn't. GL 581's radial velocity is about 10 km/s or 1/30,000 times the speed of light. That means over sixty-five million years, it has moved almost 2200 light years from our perspective (As well, the Milky Way has rotated about one quarter since the dinosaurs got killed: Sol and GL 581 were both about 40,000 ly anti-spinward from where they are now).

Also posted at Dreamwidth, where there are comment count unavailable comment(s); comment here or there.

Well, yes, but something else would have been 20 LY away then.

But the bigger problem is that reaching another star system is not even remotely the same as reaching another planet.

Life bearing meteorites only arrive when the stars are right?

I am not sure how many $10^{10}$\ is as I am unfamiliar with the $\ system of measuring stuff.


Looks like a mark-up in TeX or something for an exponent that hasn't been properly HTMLed.

As to the stars moving, it's impossible to tell from the abstract, but I feel likely that they're using GL581 as an example of a typical target for their calculations, and not as an actual target. Though the mixing of stars should probably affect the propagation somehow.


Yes, that's TeXlike, equal to ten billion. The $s set it off from regular text as a math expression, the {} means "do this to all the stuff inside the {}, not just the next character", ^ is exponentiation, and the {\ } is a space after the expression in case TeX wanted to space it differently somehow.

--Dave

Well, yeah, stars move and millions of years ago Gl 581 wan't near the Sun in interstellar terms. But the context makes pretty clear what the authors need is an estimate of how far matter would have to travel to get from one life-tolerable system to another, and they're making the guess that the present distance to the apparently nearest life-tolerable system is typical. They need some estimate of how far the particles have to transfer; what's a better estimate?

The $10^{10}$ is LaTeX code to typeset the enclosed neat and pretty as a ten with a ten superscript. The \ following I believe is a stray bit of LaTeX meant to ensure there'll be a space after the number, but I can't swear to that offhand since I prefer the \( ... \) format instead and don't worry about ensuring spaces after math inserts.

They should make it clear they mean a star like GL 581 because otherwise some SF writer is going to read this paper and not only use it as the basis of a very badly thought-out panspermia book in which protosimians were blasted across interstellar space 65 million ago, they will also think Alpha Centauri has been nailed in place 4 LY from us for the last four billion years. I'm only protecting the genre here.

Do you really think that the kind of author who would make that kind of mistake would read deeply enough to avoid it even if the authors put a flashing, scrolling banner in the abstract?

I'm thinking of Dan Simmons putting Epsilon Indi and Epsilon Eridani about a half light-year from each other in one of the Endymion books on the basis of some list of the nearest stars' distance from Sol.

Hey, they're both in the Epsilon system, right?

The journal is also quite dodgy. I would not recommend submitting a paper there.

Ah. Yes. Rather like quoting Medical Hypotheses.

Oh, wait. Wickramsinghe. This is more of Hoyle's "The Big Bang is too religious for me, therefore it didn't happen" steady-statism, isn't it.

(for the uninitiated: steady-staters have a vested interest in proving the universe must have an infinite age. As they have no evidence in favor of this assertion, they have developed a fascination with attempting to demonstrate this indirectly, by attempting to prove life is too complex for abiogenesis ever to have taken place. As they have no evidence in favor of this assertion either, they have developed a fascination with attempting to demonstrate this indirectly, by attempting to find a theoretical framework for claiming a possible extraterrestrial origin of early life.)

It seems to me this will not be fully sufficient. Abiogenesis on Earth might be fine, but just saying life dropped in from elsewhere doesn't solve anything; it just moves the question elsewhere.

To avoid the problem there should be no abiogenesis event at all. Perhaps one of these notional bacteria-laden meteors should take a timelike trajectory past a large black hole, emerging vastly earlier in the history of the galaxy? If one invokes a closed time loop, there need be no beginning found anywhere.

Panspermia does serve to deflate the argument that there's unlikely to be life elsewhere in the galaxy, though. It could be that life starting is unlikely, but that once it does, it spreads across the galaxy. So the anthropic argument would be that we're in a lifebearing galaxy due to the anthropic selection effect, not that we'd be on a lone lifebearing planet.

BTW, I suspect it's easiest to propagate life to a just-forming stellar system, when there's still enough gas around to help capture passing rocks/dust. So we'd expect in most cases planetary systems would be seeded right at the start, if they are seeded at all.

No, agreed - it's certainly not sufficent. The argument goes "abiogenesis is impossible, therefore life is only possible if it is infinitely old (or the result of a time loop, but let's not get too wacky)." A plausible panspermic model would be a step in their direction - not enough to conclude anything on its own, but it would at least be a straw at which to grasp.

I take the trouble to know about this only because Hoyle - for whom the Big Bang was unacceptable because of its perceived religious notions of a First Cause - has gotten himself used by creationists in their attempt to declare evolution invalid through assertion that abiogenesis was impossible; he was the go-to "see, we have a scientist who agrees with us, when the light is dim and you squint" for out-of-context quotes for a while.

Serves him right. Evidence leads where it leads.

From what I can tell, the lead author's main work in the past has been on cosmic strings in otherwise standard (Big Bang) cosmologies, plus a few more recent preprints about black hole entropy. So I don't think this paper is necessarily coming from a steady-state perspective. (Though, yes, Wickramasinghe was a longtime collaborator of Hoyle's, and he is a steady-state advocate.)

Actually, the big bang is consistent with a kind of version of steady state. See "Eternal Inflation". The unending expansion would occur in a very early epoch of the universe during which conditions would be totally unsuitable for life (or even atoms) to exist.

BTW, did you get that link from the Technology Review's arxiv blog? The previous entry is also interesting.

http://www.technologyreview.com/blog/arxiv/27715/

Some of the estimates there make me think that interactions with dark matter may make relativistic interstellar travel impossible.

You're just saying that because you're jealous of my dark-matter Bussard ramjet.

Are there racist implications to that?

Well, the dark matter is in the majority, while the light matter is the minority....

But note that a dark-matter ramjet allows one to have stealthy space rockets!

--Dave, you know we do this just to see you flinch, James