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Genetic Building Blocks Found In Meteorite
FiReaNGeL writes to tell us scientists have confirmed that the components of genetic material could have originated in a place other than Earth. A recently published report explains how uracil and xanthine, two basic biological compounds, were found within a meteorite that landed in Australia. From Imperial College London:
"They tested the meteorite material to determine whether the molecules came from the solar system or were a result of contamination when the meteorite landed on Earth. The analysis shows that the nucleobases contain a heavy form of carbon which could only have been formed in space. Materials formed on Earth consist of a lighter variety of carbon."
I think they mean the carbon 13 to carbon 12 ratio is not "earth normal".
IANAB (I am not a biologist), but I think that when scientists talk about "life coming from space" they mean "complex carbon compounds that could, given the circumstances, combine into self-replicating structures that would, some time later, become living organisms". In other words, the secret ingredient needed for life to appear on Earth.
But thinking "ZOMG there were living cells in the meteorite!" is just crossing the line.
Exactly. The popular writeup was terrible, but the actual paper explains that the ratio of C-13 to C-12 was 44.5% higher than earth-normal for the uracil and 37.7% higher for the xanthine.
a meteorite that landed in Australia...
landed you say? fascinating indeed.
Of course that would be silly. The living cells trapped inside the meteorite would have been baked into the material these researchers found. It's the light fluffy life forms on the exterior of the meteorite that would have been brushed off the surface of the meteorite on first contact with the atmosphere and drift gently down to the nutrient rich sea that covers most of our planet. There these hypothetic organisms would breed and diversify until they filled every sea, covered every continent and dwelled deep within the crust.
Eventually a form would evolve, such as a lichen or mold, that bred with colonies so small and potentially electrostatically charged by sunlight that they might rise to the highest reaches of the atmosphere - to be scooped up by passing meteors on their way to the unknown depths of space. Perhaps they might by a fluke of trajectory be thrown clear of the solar system altogether. Frozen in the cold of space these breeding colonies might last millions of years. The vast majority of these would wander 'twixt the stars eternally, finding no place they might rest or fall on a hostile environment and die. Given enough of them, though -- perhaps millions an hour for a billion years -- some few might land someplace they can start anew.
It's called panspermia
Help stamp out iliturcy.
Organic material coming here on comets and meteorites is perfectly plausible. But life coming from outside the solar system seems to be quite unlikely.
There was some paper released last year showing that gene degradation when exposed to cosmic rays happens at an astonishing rate. When compared to how long it would take a piece of rock to travel from even the nearest star, it just looks to be implausible at best. Not only that, it would assume that the life would be able to survive the impact and either be compatible, or adapt from the rock/ice quickly to the earth.
Even if panspermia was a viable idea, it would only say something about where life arose. It doesn't answer the question of how life arose. But if it arose here, then it would be easier to find the how. If life arose elsewhere, then we wouldn't know
To many people the term 'skeptic' has come to mean someone who disagrees, logic and training don't come into it. However skepticisim is an integral part of science and every scientist worth their salt practices skepticisim on their OWN ideas before using it to attack the ideas of others. The term the GP was looking for is 'psuedo-skeptics', ie: a person who fails to be skeptical of what they themselves 'know' and does not entertain criticisim. The worst kind of 'skeptic' is a denier, ie: someone who is willfully ignorant.
... when awesome technological powers are in the hands of a very few, and no one representing the public interest can even grasp the issues; when the people have lost the ability to set their own agendas or knowledgeably question those in authority; when clutching our crystals and nervously consulting our horoscopes, our critical faculties in decline, unable to distinguish between what feels good and what's true, we slide, almost without noticing, back into superstitions and darkness."
Personally I am skeptical that any individual fits neatly into one category althogh I do agree fundamentalist nut jobs are an 'edge case'.
Carl Sagan's book on the subject is a great read and can speak for itself...
"Science is more than a body of knowledge; it is a way of thinking. I have a foreboding of an America in my children's or grand children's time
OTOH, a skeptic might argue that Sagan's forboding is, and always has been, the status-quo.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Actually, I'd argue that it's both rather expectable _and_ at the same time meaningless.
The basic nucleotides and aminoacids can be formed rather quickly even in a retort in the lab, given the right conditions (similar to those of primal Earth). But even that is somewhat misleading: really they just need a lot of energy. Carbon and nitrogen just tend to do that, and we're talking simple building blocks, not a whole ribosome.
What took an awfully long time is those actually becoming _life_. I.e., those assembling, by sheer chance, in a self-replicating configuration.
Really, there's nothing special about finding isolated aminoacids or nucleotides. They're not yet life, they're the Lego blocks that actual life is made of. Aminoacids are not a miracle by themselves, but in the fact that they can be assembled in proteins that can react with any chemical you wish. Or produce another chemical that reacts with it. Including assemble other proteins. Nucleotides are even more meaningless by themselves. They can form a RNA strand, which is what the first and simplest life used. But the RNA strand does nothing whatsoever by itself. It needs some proteins that (A) replicate it, and (B) translate it to other proteins, before it can count as life.
The "miracle" isn't when you have aminoacids and nucleotides. It's when you have at least some kind of RNA replicase and some kind of a ribosome.
So basically "ZOMG, we found a nucleotide on a meteorite" is simultaneously:
1. not that surprising, since really they form anywhere.
2. rather meaningless for life on Earth, in that we have plenty of proof that they formed withing minutes on Earth too, with the conditions back then. So a couple of those molecules maybe came on a meteorite too. Big deal, compared to the whole billions of tons of them forming right here.
3. rather unlikely as a source of life on Earth. Sooner or later those molecules break down. They don't last for ever. And we're not talking self-replicating life, but some building blocks which still needed to combine into a configuration that can be called "life", by sheer chance. That means lots and lots of them, and lots and lots of time. It's kinda absurd to assume that meteorites kept bringing billions of tons of them, for billions of years, until they finally recombined into some kind of ribosome.
4. it at best brings some extra insight into it all. If they're as easy to form as to even exist in meteorites, well, it just makes it easier to believe that we had a lot here too. In fact, maybe we had them earlier than we thought, as Earth itself formed out of dust which coalesced into meteorite, which coalesced into a planet. The last one captured was the one that ejected a chunk of Earth and created the Moon. So maybe we had some building blocks before Earth even formed. It also means we can expect almost any planet anywhere to have _some_ of the building blocks, and evolve life, if the conditions and timing are right.
But again, not an awful lot of insight that we didn't already have anyway.
A polar bear is a cartesian bear after a coordinate transform.
the so called hostile temperatures on earth are nothing compared to the hostility of the environment in space.
massive radiation, shockwaves, coronal mass ejections, MASSIVE extremes of heat and cold, and very importantly, the tendency for water to remain in a vaporous or solid form rather than liquid because of the lack of pressure.
Not to say the first dna fragments, amino acids, or single celled life forms could not have come from space, but they had to develop on some body with enough gravity and atmospheric pressure to host some liquid water water.
This characteristic need for liquid water is too fundamental to have simply arisen after this life came to earth.
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Whole microbes surviving in an airless, nutrientless, radiation-saturated enviornment is not unprecedented. The Apollo 12 crew found scores of living streptococcus mitus doing just fine on the Surveyor probes on the moon, which had been there for three years. While its doubtful whole cells came here and populated the planet, it also seems unlikely that the Earth alone provided all the ingredients.
I find it really, really disturbing that people labeled "scientist" continue to have a go at the outer space theories. Out of all PhD:s in science I have met and the topic has been brought up I have never met anyone who believed in actual life coming from outer space, or that extraterrestrial material in fact would have been needed on a primordial Earth in order to create life. That a US president was blatantly fooled into promoting that childish Mars rock theory from a decade ago still hurts my mind. Think Occam's Razor. Dig where you stand. Don't overdo it, son.
Yeah, I tend to think that evidence like this of organic compounds in meteorites is looked at more as proof that they are formed (and distributed) routinely throughout the universe, rather than trying to say that this was the mechanism by which they arose on Earth. This has pretty serious implications for things like the Drake Equation, or at least the likelihood of planets with habitable climates having access to the materials necessary for life to come about.
Recursive: Adj. See Recursive.