Comets spread Earth-life around galaxy, say scientists

Cardiff University ^ | 10 February 2004 | Staff

[PatrickHenry]

If comets hitting the Earth could cause ecological disasters, including extinctions of species and climate change, they could also disperse Earth-life to the most distant parts of the Galaxy.

The "splash-back" from a large comet impact could throw material containing micro-organisms out of the planet’s atmosphere, suggest scientists from Cardiff University Centre for Astrobiology.

Although some of this outflowing material might become sterilised by heat and radiation, they believe that a significant fraction would survive. As the Earth and the Solar system go round the centre of the galaxy every 240 million years, this viable bacterial outflow would infect hundreds of millions of nascent planetary systems on the way. Hence, they suggest, the transfer of Earth life across the galaxy is inevitable.

These ideas are discussed in detail in two papers appearing in the current issue of the Monthly Notices of the Royal Astronomical Society.

The authors of the two papers are Professor Chandra Wickramasinghe and Dr Max Wallis, of the Cardiff Centre for Astrobiology, and Professor Bill Napier, an astronomer at Armagh Observatory and an Honorary Professor at Cardiff University.

Interstellar routes for transmission of micro-organisms supports the view that life may not have originated on Earth but arrived from elsewhere, strengthening the "panspermia theory" that Professor Wickramasinghe and the late Sir Fred Hoyle had been developing since 1974.

It is known that boulders and other debris may be thrown from the Earth into interplanetary space. Professor Napier finds that collisions with interplanetary dust will quickly erode the ejected boulders to much smaller fragments and that these tiny, life-bearing fragments may be driven out of the solar system by the pressure of sunlight in a few years.

The solar system could, therefore, be surrounded by an expanding `biodisc’, 30 or more light years across, of dormant microbes preserved inside tiny rock fragments. In the course of Earth history there may have been a few dozen close encounters with star-forming nebulae, during which microbes might be injected directly into young planetary systems.

If planets capable of sustaining life are sufficiently common in the Galaxy, the Cardiff based scientists conclude that this mechanism could have infected over 10,000 million of them during the lifetime of our Galaxy.

Dr Wallis and Professor Wickramasinghe have also identified another potential delivery route. They point out that fertile Earth ejecta would, on impact, bury themselves in the radiation-shielded surface layers of frozen comets. A belt of such comets, the Edgeworth-Kuiper belt, lies beyond the planetary system. This belt gradually leaks comets into interstellar space, some of which will eventually reach proto-planetary discs and star-forming nebulae. There they are destroyed by collisions and erosion, releasing any trapped micro-organisms and seeding the formative planetary systems.

[PatrickHenry]

Bold font added by your humble poster. Everybody be nice. Remember, we are all citizens of the "biodisc."

[PatrickHenry]

PING. [This ping list is for the evolution side of evolution threads, and sometimes for other science topics. FReepmail me to be added or dropped.]

[Seruzawa]

Unless it's life from somewhere else that settled here.

[VadeRetro]

Although some of this outflowing material might become sterilised by heat and radiation, they believe that a significant fraction would survive.

I think here's the crux. We obviously exchange some matter with interstellar space. Whether anything could survive the pulverizing impacts, the radiation, the long times involved, etc. is another question.

[PatrickHenry]

The article mentions that. Sometimes, you gotta read it all the way through.

[js1138]

Unless it's life from somewhere else that settled here.

That possibility is addressed in the article (if you know what to look for).

[PatrickHenry]

Whether anything could survive ...

Most won't. The fittest will. We are the descendants of the toughest spores in the galaxy.

[Shryke]

Very interesting article. It would kind of underwhelm me, though, to discover that other life forms on other planets look just like us*. "Space Humans from Andromeda" sounds sorta hokey.

*Yes, I know, there is no reason why, given common microbial DNA sources, other planets wouldn't produce newer life forms. It just leaves the possibility of a human-type life form that much more possible.

[Seruzawa]

Okay, got it, thanks.

Need coffee. More coffee. MMmmmmmmmmm.....

[VadeRetro]

We are the descendants of the toughest spores in the galaxy.

You know how you look at some people and say, "It's hard to believe he beat out 2 million other sperm?" We are the degenerate, gone-soft, unworthy descendants of the toughest spores in the galaxy.

[American_Centurion]

Here is a list of stars within 50 light years of us.

I don't expect that during the millions of years there has been life on earth, especially considering that during at least half of that time the "bio-disc" would have only expanded to reach the 26 nearest stars that we would have passed near enough within the period of life to "infect 10,000 million" systems.

[PatrickHenry]

It would kind of underwhelm me, though, to discover that other life forms on other planets look just like us.

They probably won't look just like us. Everything on earth presumably got going from the same start, and we don't look like fish, or spiders, etc. However, it's comforting to know that even if they don't look like us, they should be edible. (And vice versa, of course.)

[American_Centurion]

I would like to correct something from my previous.

The article estimated the "bio-disc" to be maybe 30 LY accross so that would mean that only stars within 25 LY of us now would be able to contact it, which would mean half-way back though the period of life the bio-disc would be less than 7.5 LY accross or less, making half of the 26 nearest stars unreachable for half the period of life meaning my math was off by several orders of magnitude. But you get the picture right?

[American_Centurion]

Need proof reading leassons.

25LY should be 15LY.

[Sabertooth]

Bold font added by your humble poster. Everybody be nice. Remember, we are all citizens of the "biodisc."

Try it this way:

"If planets capable of sustaining life are sufficiently common in the Galaxy, the Cardiff based scientists conclude that this mechanism could have infected over 10,000 million of them during the lifetime of our Galaxy."

Now, try this:

"At the rate we're finding If planets capable of sustaining life are sufficiently common in the Galaxy, the Cardiff based scientists conclude ...."

"10,000 million" of them is as scientific a statement as the fold-ins on the back cover of a Mad Magazine.

[American_Centurion]

leassons --- ok, I give up!

[Verginius Rufus]

This is all George W. Bush's fault for tossing out the Kyoto Protocols.

They claim that some meteorites found in Antarctica came from Mars, so this latest claim doesn't sound all that far-fetched.

[sgtbono2002]

Sounds like a pretty far flung idea to me, ( pun intended)

[AndrewC]

Mars is a bit closer than most stars, I believe. It should be literally coated with bacterial slime from Earth if this hooter of a theory is true.

[Gefreiter]

Great article, but it leaves me wondering who Jesse Jackson can sue over the lack of biodiversity in the galaxy.