I don’t remember when I first heard the theory that life could have evolved on Mars and traveled to Earth by way of meteorite, a theory which a commenter on my livejournal points out is called panspermia. I’ve always thought panspermia was pretty far-fetched, but apparently it’s close-enough fetched that scientists are testing its viability.
Scientists at the University of Aberdeen are investigating whether life can travel between planets via meteorite, including whether or not it could have traveled from Mars to Earth. Investigating the later claim, they sculpted a slab of rock into a particular shape, and are attached it to an unmanned Russian craft.
Further details of the experiments are to be revealed later, but the scientists already have some theories about what a meteorite that could carry life would have to look like:
Prof Parnell said primitive life could not survive a meteorite of small size because of the heat, but believed it could survive inside the centre of a larger one measuring tens of centimetres.
UPDATE: In comments, Robert and Ron try to correct my ignorance on the issue. Robert writes:
It’s a numbers game. Simplifying assumption: the transport mechanism is viable, widespread, and easy/automatic – impacts on planetary surfaces that carry life-bearing rock out into deep space is pretty good as far as those go.
With that assumption in place, then life can start anywhere in the universe and spread through the transport mechanism. The initial “invention” of life remains very unlikely, but you have trillions of potential places for it, instead of just one. “It happened somewhere else and then drifted here” is much more likely than “it happened here”.
The analogy I like to use is rock music. Is there rock music in your town? Sure. Was it invented there? No, it was invented in (a hundred) other places, and CAME there. It’s a more likely scenario that you live in a place that has bands who were inspired from some outside source, than it is that you have bands who invented it themselves.
There was an article about this in Scientific American a while back – I’ll have to look through my back issues. Scientists have found (and still find) meteorites whose origin is Martian in Antartica – black rocks stand out on white ice. The consensus is that it’s definitely possible that microbes (especially bacterial spores) could withstand the trip.
Also: the various current Mars missions have revealed that there was definitely running water on Mars’ surface in it’s history. There is also growing suspicion that there is liquid water below Mars’ surface right now. If so, there could be microscopic life (at least) in Mars right now.
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Ron,
That’s what I’d understood. I just don’t know why panspermia as an origin theory is any more plausible than life starting on earth. It reminds me of those arguments about how God was created. “If it’s not clear how we generated, so there must be a God, then how was God generated?” I’d rather keep the impossibility close to home instead of flinging it a couple iterations of impossibility away. Call it occam’s razor of creation theory.
I love the water thing. Edgar Rice Burroughs for the win.
I just don’t know why panspermia as an origin theory is any more plausible than life starting on earth.
It’s a numbers game. Simplifying assumption: the transport mechanism is viable, widespread, and easy/automatic – impacts on planetary surfaces that carry life-bearing rock out into deep space is pretty good as far as those go.
With that assumption in place, then life can start anywhere in the universe and spread through the transport mechanism. The initial “invention” of life remains very unlikely, but you have trillions of potential places for it, instead of just one. “It happened somewhere else and then drifted here” is much more likely than “it happened here”.
The analogy I like to use is rock music. Is there rock music in your town? Sure. Was it invented there? No, it was invented in (a hundred) other places, and CAME there. It’s a more likely scenario that you live in a place that has bands who were inspired from some outside source, than it is that you have bands who invented it themselves.
All right, that’s a fair explanation. Thanks!
(I think I’ll update the post with it.)
Viewed from the opposite direction, it greatly increases the chance that there is life out there somewhere. The chance that there is life here is 1 out of 1, and the chance that a place where there is life will be a place where life has evolved (given no other mechanism) is 1 out of 1, but if the chance of life evolving on a given rock is very very small, then the chance of there being lots of life elsewhere is very very small. However, if life can spread between systems when it is still in the bacterial stage rather than in the post-human stage then that increases the chance that there are lots of other worlds that were seeded and had a chance to produce intelligent life.
I don’t know about that. Unless we find life elsewhere its unnecessary. If it didn’t happen here then we would not be around to say “gee life is so rare its unlikely that it happened here.” Its kind of a derivative of the anthropic principle.
Charles,
I’ve always gotten that end of the argument, which is I suppose why I’ve viewed the theory as far-fetched optomism. Nice, yes. But “I want aliens” is not necessarily a good argument for why something is likely.
Though, really. I do want aliens.
I do want aliens.
Even if they show up to proselytize?
It’s not part of the panspermia theory proper, but there is a subset of the idea called directed panspermia – there’s the random stuff happening, but there’s also some aliens out there deliberately seeding rocks and shooting them out into interstellar space.
Such an effort would be very resource-intensive, I would think. And – assuming that it’s not the equivalent of an intergalactic Safeway sending out seeds for later harvesting of biomass – one of the better rationales for such activities would be religious. As in, “God wants us to fill up the universe with life, so let’s get cracking on these bioasteroids.”
“There is also growing suspicion that there is liquid water below Mars’ surface right now. If so, there could be microscopic life (at least) in Mars right now.”
The same is actually true of Europa, one of Jupiter’s moons, which very likely hosts an ocean of liquid water underneath its surface of ice. An interesting thing about it is that if there is life on Europa – which I hope there is, because the universe can get so lonely sometimes – it will have been heated not by the Sun, but by gravity. (The push-pull effects between Jupiter’s gravitational pull and that of its nearby but less massive fellow moons oscillates Europa’s barycenter, creating seismic waves. The friction heats the moon.)
This opens up the possibility that life may leapfrog from the outside of a star system toward the inside, following the inward migration of asteroids.