Did a Cooked Meteorite Seed Life on Earth?
Written by Ian O'Neill
Earth, four billion years ago, was a lifeless, hot and violent place. Not exactly a world where you'd expect life to form. But this was the scene where the first life-forming amino acids appeared. And how did this happen? According to new research, a lump of rock floating though space may have been irradiated by neutron star emissions, chemically altering amino acids hitching a ride on it. This rock then impacted the Earth and injected these altered chemicals into the desert wastes, possibly seeding the beginning of life on our planet… and this life was left-handed…
We've heard about this possibility before: life on Earth being seeded by some extra-terrestrial body, like a comet, meteorite or asteroid impact. In fact the prime reason for analysing comets and objects in the Oort Cloud (hovering around the outer reaches of our solar system) is to look for pre-life chemicals and organic compounds such as amino acids. Indeed, the discovery of organic compounds by the recent Cassini flyby of Saturn's moon last month is another piece in the puzzle toward understanding the extent of life-giving chemicals on planets other than Earth.
Amino acids are a type of protein found in all life forms on Earth, it seems reasonable to search for the presence of these proteins on bodies other than our planet, possibly giving us more information about how life formed and where life came from.
There are two forms of amino acids, one left-handed and one right-handed, giving an indication of the orientation of the acid. For life to be seeded, these proteins must contain only one "chirality" (i.e. either left or right), it's no good having mixed chirality.
At the 235th national meeting of the American Chemical Society, new research has been presented describing how our amino acid signature may have come from outer space. Ronald Breslow, a university professor at Columbia University points out that the vast majority of life on Earth has a "left chirality". And his reason for this? The polarized light emitted from neutron stars many billions of years ago irradiated rocky bodies, with amino acid compounds on their surface, selectively destroying most of the "right-hand" acids. Although this theory may sound outlandish, it does give a possible reason for the prevalence of left-hand proteins in amino acids on Earth.
The irradiated meteorite will have impacted the Earth carrying amino acids with a dominance of left chirality which dropped into the "primordial soup", evolving into the first forms of life. All life as we know it will have the same chirality as this soup of pre-biotic life.
"These meteorites were bringing in what I call the 'seeds of chirality' [...] If you have a universe that was just the mirror image of the one we know about, then in fact, presumably it would have right-handed amino acids. That's why I'm only half kidding when I say there is a guy on the other side of the universe with his heart on the right hand side." – Ronald Breslow.
Breslow and his team simulated the events after such a meteorite hit the surface. As the left-hand dominated amino acids from space combined with existing amino acids (of mixed chirality) on Earth, the desert-like temperatures and a dash of water amplified the left-hand proteins, giving them dominance, thus sparking the basic building blocks of life. He argues that these acids were most likely brought to Earth via meteorite, and not chemically altered by radiation in-situ, "…the evidence that these materials are being formed out there and brought to us on meteorites is overwhelming," said Breslow.
Source: Physorg.com
Filed under: Astronomy
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April 6th, 2008 at 4:59 pm
Interesting theory… I'd be keen to read more about the proposed mechanism and the reasons for its favouritism of left-handed chirality of amino acids.
April 6th, 2008 at 6:13 pm
"Amino acids are a type of protein found in all life forms on Earth"
Actually, amino acids are what make up proteins…. proteins are basically just long chains of amino acids which are folded up in specific ways.
April 6th, 2008 at 7:14 pm
Wouldn't a meteorite drifting past a neutron star be rotating in some way? Unless it is tidally locked (and unlikely to escape). If so the polarization would change as the meteorite rotates or tumbles. How could it then give rise to left handed amino precursers?
April 7th, 2008 at 4:24 am
In other words, just the right clump of rock, passed just the right neutron star, at just the right time, at just the right angle, for just the right amount of time, on just the right course, to impact Earth at just the moment it became able to host life. Then within approximately 150,000 years life becomes world wide and genetically varied. "Interesting." No stretch of creditability at all, right?
April 7th, 2008 at 5:20 am
Yes it is all a bit sketchy. Breslow maybe a professor of chemistry, but his info on the chirality of meteorite seems to be lacking basic review. A couple of examples 1- Murray CM2 – 7racemic (equal) amino's 11-non protein amino's. 2-AH 77306 – racemic. 3-Murchison (Nature230, 105-106 (mar 1971)- racemic, 70 amino's total, only 8 found in terrestial proteins. He's trying to turn a small excess into a major force.
April 7th, 2008 at 5:30 am
Interesting theory. Just because it sounds incredible, doesn't mean it's not true. BUT (and it's a big 'But'..), it'll be interesting to see if he can find a method of exprimentally determining if the theory holds up.
Simulations are one thing, actual evidence is another matter entirely.
April 7th, 2008 at 6:28 am
My comment is a question. What if right hand chirality had been dominant. Would life have been different (possibly more Republican based)? Seriously, any difference?
April 7th, 2008 at 7:11 am
Everyone has seen "The Fly" right? I read somewhere that there is another wicked transporter trick and that would be to have that transporter (by accident or by design), reverse all of your moleculars so you were R-isomer based instead of L-isomer. Then you would eat and eat and not gain an oz. Instead, you would starve to death as your body would not use the L-isomer stuff that all of our life used.
Wicked fiction – and I don't even think it was Harlen Ellison. I can remember. And thanks, Mus for beating to the animo acid faux pas.
April 7th, 2008 at 9:00 am
probably safer to do the transport trick on every other meal (like, dinner) and leave breakfast and lunch alone. A whole new market for 'weight-gain-free' food.
April 7th, 2008 at 10:35 am
Omigawd! That could led to anorexia nervorsa transportis! And think of the electric bill!
April 8th, 2008 at 12:03 am
Are all planets seeded and only a select few allow life to get a toe hold? Where did the seed come from? How did it have amino acids to begin with?
Working our way back, back, back, back to the absolute origin of life itself in any form is all I'm interested in. With so much inorganic in the universe, where did the organic come from!?!?!? It drives me crazy. I guess if I had an answer I'd be famous.
May 11th, 2008 at 5:09 pm
Delbert Freeman, you know how complex life is on this planet? the mathematical formula involved in creating you..the perfect circumstances occurring for life to take the forms it has today?..i would say the probability of the above taking place is much more favorable than life recurring to the exact specifications as on Earth.
Anyway. it's much more believable than the bible.
January 11th, 2009 at 9:32 pm
Delbert Freeman, what kind of comment is that? I suppose you will throw up some sort of "God" or "Intelligent Design" proposition (I'm not going to call those theories, they don't deserve it), if someone actually cared enough to ask for your opinion. Let me tell you one thing, the Universe is a very big and even stranger place. Shit happens. That includes really improbable shit.
April 21st, 2009 at 8:59 pm
this thing is sooooo fake dnt youu read the Bible god created the world & every thing around it so diz LIE is not worth of any onez time to read!!!!!!!!!!!!!! =[