Meteorite experiment deals blow to 'bugs from space' theory
September 25, 2008
This NASA file image shows a 4.5 billion-year-old rock, labeled meteorite ALH84001, believed to have once been a part of Mars and to contain fossil evidence that primitive life may have existed on Mars more than 3.6 billion years ago, which was found in Allan Hills ice field, Antarctica in 1984.
A novel experiment has dealt a setback to a theory that life on Earth was kickstarted by bacteria that hitched a ride on space rocks.
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10 hours ago
Nonsense. Smearing some bacteria on the rear surface of two tiny pieces or rock has no relevance to the panspermia theory. Bacteria are found living thousands of feet below the earths surface in the interstices naturally present. When the experiment has been repeated and shows that all bacteria -or bacterial spores - have been killed in the center of a 10Km wide space rock, that would be more relevant. Bad science.
Admittedly I've never been a fan of panspermia, and quite frankly always considered it fringe science....so it may just be my bias showing through.
brakes open releasing spores microbes etc. that are very light in now thick atmosphere float slowly down alive. Providing the vacuum and hard radiation of space had not killed them.
Until then its an interesting theory that may or may not have happened.
Unfortunatly the only thing this article suggests is that small meteorites are unlikely to spread life around.For some reason i suspect funding wouldnt allow the 10km rock experiment:D
Too small and the meteor burns up in the atmosphere.
Too large and the meteorite is vaporized on impact.
I have seen photos of meteorites that range in size from softballs to basket balls that left only small (less than 1m) craters if any at all. These meteorites could be porous or have deep fissures and still be large enough to insulate the interior from the heat of passing through the atmosphere. I can envision a scenario where just such a rock lands in water, snow or ice and is rapidly cooled before the interior of the meteor was heated via conduction and said space germs are cooked. Such a thermal shock could also further fracture the rock releasing the travelers to their new environment (we must assume it's not toxic to them).
Yeah the test is not conclusive but its some result at least. They should try bigger ones with bacteria placed in the center.
Very large rocks have huge kinetic energy and are vaporised on impact - nothing will survive in those.
To me the main problem with panspermia is that it doesn't solve any problems, instead it creates new ones - the life still had to start somewhere, and on top of that it also had to make an exceedingly improbable journey to Earth.
I think the reason behind panspermia is a desire some people have for a more romantic way in which life came about as well as the fact that it is more compatible with purposeful creation (by aliens, god, AI, or whatever). No trace of such a deliberate creation on Earth can be troubling for proponents of some such theories, with panspermia they can claim the creation took place elsewhere.
Wouldn't it be cheaper to simulate in a blast furnace or something?
Or is the abrasive nature of the entry also a factor?
I realize the questions may appear novice, but I'll admit I'm no astrobiologist.
many of the points above are valid and point out that the experiment is highly flawed.
...or maybe someone just didn't wipe their feet or take off their shoes (like my wife is always telling me) when they stepped on the surface 4 billion yrs ago.
Well it has to be as close to the real thing as possible, it would be very hard to precisely recreate all aspects of reentry like proper pressure profile, changing atmospheric concentration, shockwaves, abrasion, etc.
Besides no matter how hard you tried some critics would never be convinced its good enough.
(At least I think those are the reasons I'm not astrobiologist either)
What makes it so difficult to believe that life originated on Earth instead of Mars?
if it could originate on Mars, it could ALSO originate on Earth.
in fact, it could have very well originated on Earth and being transported TO MARS aboard Earth rocks expelled from Earth due to a big impact.
You observed a meteor (in flight) from 50 to 75 feet away? Sure... right...
Right... but either way its still panspermia, at least within our solar system. If it is true that life developed on one planet and then seeded another, then wouldn't you find that rather interesting?
Anyway, *WE* are outer space from the perspective of Mars.
Unless you count the possibility that our Mars landers have already contaminated Mars with Earth grown life.
A second question, WRT this experiment, is how long did they leave the Chroococcidiopsis exposed to vacuum? Anything coming from Mars would be exposed to vacuum and solar radiation for at least 6 months (and more likely years.)
Not many people if any would expect that a rock that small would not be cooked on re-entry.
And cooking will kill bacteria.
Whether Panspermia exists or not this experiment proves nothing except that cooking does in fact kill bacteria something we already knew.
Even if Panspermia is proved as feasable it does not prove that life on Earth originated elswhere.
There is nothing on the books that says life cannot be created in more than one location.
I think it's partly because life appears to have come out of "nowhere" very soon after the Earth formed.
Pretty much everyone agrees that there have been cyanobacteria at least as long as 3.5 billion years, and some evidence seems to indicate that they have been around for 3.8 billion years. That's the time when the fiery Hadean period ended and life as we know it became possible. The problem is that cyanobacteria are actually very complex organisms and the Calvin cycle they use to release oxygen requires lots and lots of evolution. Would cyanobacteria have evolved on Hadean Earth? I wouldn't bet on it.
Here's Wikipedia's entry for Calvin Cycle:
http://en.wikiped...in_cycle
As far as I know, there are three points that would make the reverse case more likely:
1. Earth is bigger and has stronger gravity, which makes it take in more rocks from space.
2. The weaker gravity of Mars means a large meteor impact on it's surface sends more rocks to space.
3. The conditions for life on Mars apparantly became favorable before they did on Earth.
According to (sourced) wiki article on hadean period liquid water already existed on Earth as early as 4.4 billion years ago (BYA).
Cyanobacteria article says the earliest evidence for life seems to be from 3.5 BYA but it is not identified as cyanobacteria which are phototrophic, evidence shows that photosynthesis evolved before 2.5 BYA but there is no proof when exactly.
All in all there is no conflict as those dates leave enough time for evolution to do its magic.
http://en.wikiped...i/Hadean
http://en.wikiped..._history
One other thing is that today's cyanobacteria are almost certainly completely different from those which first evolved.
Just as todays combustion engines are nothing like the first steam engines, the primitive life metabolism was nothing like today's sophisticated biochemical masterpiece.
Calvin cycle should be thought of as a most recent incarnation in a series of metabolic engines of increasing complexity developed during evolution.
What makes you think so? So far it seems possible that they never became favorable on Mars.
some bacteria seem to have been built for interstellar travel: survive radiation, vaccuum and cold of space, repair its DNA, and survive millions of years in a sort of hibernation.
stupid experiment though, smearing bacteria on the back of a rock? c'mon
The Hadean period, which lasted up to billion years, was a time when there was very little crust on Earth and so the first oceans were extremely hot (estimates vary between 80C and 100C), not to mention all the other types of hazards like radiation and chemicals. That's dangerous for organisms without DNA damage repair molecules and definitely too much for the molecules behind photosynthetic reactions.
The oldest known stromatolite fossils (photosynthetic cyanobacteria) are approximately 3.5 billion years old:
http://www.ucmp.b...ofr.html
There's still no denying that oxygenic photosynthesis requires a very complex set of molecules to work.
1. What makes you state this as a "fact"?
2. Why would they be more adapted to space? This would imply an organism evolving IN space as opposed to an organism evolving on a planet and being broadcast through space.
But there are two other sillynesses to the study: 1) Life could have entered when the atmosphere was vastly thinner or thicker; 2) The study assumes that it's common for material in space to carry life. But it might be only one-in-a-million. The end result, after millions of hits, would be the same.
Todays life can exist in such conditions, early life could have been even more tolerant. As for radiation most of it would be attenuated by water.
The oxygenic photosynthesis is complex, but photosynthesis when it first appeared was most likely much simpler based on something like a bacteriorhodopsin molecule - a single protein capable of converting light energy into chemical energy (proton gradient). Oxygen only started to accumulate at the end of archean period 2.5 billion years ago.
http://en.wikiped...hodopsin
LARGER ONES PERHAPS.
THE MOST PROBABLE SOURCE WOULD BE DUST PARTICLES THAT WOULD TEND TO FLOAT OR DRIFT DOWN, THUS AVOIDING THE HEAT OF RE-ENTRY AND AVOID BEING COOKED.
SPACE DUST AND COMET DUST COULD BE SOURCES
I THINK IT IS PREMATURE TO WRITE THIS POSSIBILITY OFF ON A SINGLE 2 CM SAMPLING
FRED HOYLE AND A SRI LANKAN ASSOCIATE WROTE AN INTERESTING BOOK ON PANDEMICS AS HAVING POSSIBLE ORIGINS FROM SPACE DEBRIS OF SOME SORT. A TRIP TO ONES LIBRARY MIGHT PROVE INTERESTING
Of course there could be a god. Nahhhh, that would be too simple