I’ve always found the idea of panspermia oddly comforting. Growing out of the work of Swedish chemist and Nobel Prize winner Svante Arrhenius, panspermia assumes that life can move between worlds by natural means, and implies that planets with the right conditions will wind up with living things on them. That idea of all but universal life, and the weird notion that we might all be in some way ‘related,’ was exhilarating to thinkers like Fred Hoyle and Chandra Wickramasinghe, who went on to suggest that the influx of life from space triggers continuing changes on Earth today, which might involve epidemics and new diseases.
Now comes a variant called lithopanspermia, which questions whether rocks blasted off a planetary surface by impacts might not be the transfer vehicles for microorganisms that travel between planets and perhaps further. After all, we have found Martian meteorites in Antarctica, forty or so to date, so the real question becomes the survival possibilities. Can a microorganism survive the impact of the original projectile into its home world and the journey through space, which in the case of Martian meteorites ranges from between one and twenty million years?
A study in the latest issue of Astrobiology makes the case that survival is possible. Endolithic cyanobacteria and epilithic lichens can withstand incredibly harsh conditions here on Earth and become prime candidates for investigating their potential passage through space. The team simulated shock pressures of the sort the organisms might have experienced when being blasted off the Martian surface, with results that support space transport at least within planetary systems. From the paper (internal references deleted for brevity):
A vital launch window for the escape from Earth’s gravity field may only be achieved by very large impact events that blow out at least part of the atmosphere… The direct ejection and escape of rocks from Earth is very difficult because of the required very high escape velocity (11 km/s) and the decelerating effect of Earth’s dense atmosphere. Therefore, “mega-impacts,” which occurred frequently only during the “early heavy bombardment phase,” i.e., before 3.75 billion years ago…, would be required to transfer sufficiently large fragments of moderately shocked rocks into space. Our results enlarge the number of potential organisms that might be able to reseed a planetary surface after “early,” very large impact events… and suggest that such a re-seeding scenario on a planetary surface is possible with diverse organisms.
Re-seeding a planetary surface is an interesting scenario in itself. It implies that a major asteroid strike might not spell complete doom for life on the planet, no matter how devastating the effects on the surface below. Rocks eventually falling back to their home world have the potential for launching life processes all over again. And, of course, the concept of life moving between entirely different planets receives another boost from this work, which gives “…further support to the hypothesis of lithopanspermia for a viable transport from Mars to Earth or from any Mars-like planet to another habitable planet in the same stellar system.”
The paper is Horneck et al., “Microbial Rock Inhabitants Survive Hypervelocity Impacts on Mars-Like Host Planets: First Phase of Lithopanspermia Experimentally Tested,” Astrobiology Vol. 8, No. 1 (2008), pp. 17-44 (available online).
Hi Folks;
The Milky way is roughly 100,000 light years in diameter. If lifeforms could propagate on average at a rate of 3 kilometers persecond throughout the galaxy starting at one end of the galaxy, in (100,000)/(100,000 EXP – 1) years or 10 billion years, life could have spread to every habitable planet within the Galaxy. Since the random relative motions of the stars tend to be considerably greater than 3 Km/ sec, the timeframe for spreading life throughout the Galaxy is considerably less.
The possibility of exotic viruses or hardy bacteria, even dangerous fungi-like organisms, occasionally being introduced to the Earths biosphere from outer space presents a certain level of danger which should not be entirely overlooked. While the Blob in the movie by that name may seem a little far fetched, other organisms that can react with or injest protein, carbohydrates, and fat could pose a danger especially if they were foriegn in nature enough so that our bodies natural defenses would not know how to recognize such lifeforms or their biochemical markers. It might be possible that very virulent micro-organisms as such exist in dormant form within blown out planetary debris originating from other star systems just floating inside the space rocks around the galaxy. If these organisms do infact exist, it is anyones guess as to how they would infect humans or Earth based animals, let alone the mortality rate of infection, and the mean duration of illness caused by such organisms.
Thanks;
Jim
Earth may have already been seeded with a cometary panspermia sort of event.
“The red rain phenomenon of Kerala and its possible extraterrestrial origin”
http://arxiv.org/abs/astro-ph/0601022
“New biology of red rain extremophiles prove cometary panspermia”
http://arxiv.org/abs/astro-ph/0312639
“Cometary panspermia explains the red rain of Kerala”
http://arxiv.org/abs/astro-ph/0310120
One wonders how small a rock could be to provide a spaceship for a germ .
That recent grab of comet dust may have brought back particles that were “armor” enough for something to survive inside the motes. Then there’s the moon rocks, and soon enough, fresh juicy Martian rocks too — not just those old ones that landed here.
But who are we kidding? Some sort of singularity is predicted for us — soon, and germs from space may be the last thing on our minds 20 years hence. Heck, we could have finally pieced together a Tyrano-Rex DNA and nudged some crocodile to birth in twenty years, and then, yep, hunting preserves, and finally “Reptiles on a plane!
The Earth has been germified since day one, therefore, so far so good — seems like 5 billion years is a good longitudinal study about the virility of alien germs — even if they killed the dinosaurs, life here found away to deal with them eventually. I’m putting my money on life!
But, as tough as life is, I’ve got bigtime doubts about it being able to hibernate across the intergalactic divides. Instead, I hold that life is, indeed, spontaneously arising almost everywhere everywhen and by every way.
Or, you know, UFO’s are tending their Earth garden, and we’re all from seed stock originally found under a rock in the outskirts of Andromeda by a kid with a bad ‘tude and a tentacle up his nose.
Edg
For some reason, India seems to be source of a number of rather dubious science stories. Perhaps they are all just part of the growing pains of becoming a world power in science and technology.
And regarding re-seeding experiments… count me out!
My question about interstellar panspermia is whether such microbes, even buried inside meteoroids, would be sufficiently shielded against the intense cosmic radiation you’d find outside a stellar magnetosphere. Presumably, the longer an interstellar journey takes, the lower the survival rate for microbes would be as more and more of them get struck by energetic cosmic rays. So if panspermia could occur, it might be on more of a “local” scale, galactically speaking — only those star systems close to a planet with the right conditions to spawn these “lithopanspermic” meteoroids (panspermoliths?) would end up being seeded. (Close during the epoch that the panspermolith production occurs, that is.) This would reduce the risk of panspermic contamination of any given world. It would also either reduce the number of life-bearing worlds galaxy-wide (if the origin of life is a rare event) or increase the number of distinct, independently originated panspermic “superkingdoms” (if life can arise fairly easily).