The origins of life on earth are a hotly debated topic among scientists. One theory suggests that, even if whole organisms didn't come to earth carried by meteorites, then maybe meteorites brought some of the chemical building blocks for amino acids – the molecules that make up proteins. Now tests on a meteorite with the catchy name CR2 Grave Nunataks 95229 provide more evidence that meteorites might have brought these building blocks to earth, kickstarting the chain of events that led to the evolution of life here.
CR2 Grave Nunataks 95229 is a type of meteorite called a carbonaceous chondrite – meteorites that contain a range of organic chemicals including amino acids. Because of this, some scientists think that they might have 'seeded' earth with these chemicals when they fell from space, providing the primitive building blocks for the formation of DNA and proteins, which ultimately led to life as we know it. But studies of similar meteorites haven't come up with solid evidence for this, as the chemicals they contain are a real mix of all kinds of things – most of which couldn't easily be used to create molecules of life.
The Grave meteorite spun off from an asteroid and landed in Antartctica in 1995. Researchers, led by Sandra Pizzarello and her colleagues in the US, analysed the chemical makeup of the meteorite using high pressure water at a temperature of 300 degrees centigrade – conditions designed to mimic both the asteroid where the meteorite was made, and the conditions on the early earth.
Publishing their results in the journal PNAS this week, the team discovered that their asteroid contained surprisingly high amounts of ammonia – a chemical precursor to amino acids. These levels were much higher than might be expected on earth at the time.
Given the chemical makeup of similar meteorites, and the fact that most of these only contain compounds built of rings of carbon atoms, this is an unusual find indeed, and the first of its kind. Further analysis showed that the ammonia in the meteorite could only have come from the original asteroid it came from, and suggests that there was a lot of ammonia around in that environment.
Nitrogen, which is a key part of ammonia, is the fourth most common reactive element in the universe. Here on earth, it's a vital component of proteins, as well as DNA and RNA – the genetic information within living cells – and it's indispensible for life. Ammonia plays a key role in many chemical reactions, including the reactions that create the molecules of life.
But from what we know of the conditions on the early earth, it's been hard for scientists to figure out how this might have worked back then. For a start, evidence suggests that the early earth's atmosphere wasn't relatively rich in ammonia. And we know that sunlight can also break down the chemical, which would have been a big problem at the time.
But the discovery that meteorites can actually contain relatively large amounts of ammonia suggests an alternative route for the chemical to turn up and get involved in the chemical reactions that might have led to the generation of the molecular building blocks of life all those millions of years ago. And it adds weight to the idea that at least some of the molecules that kickstarted life on earth may have come from space.
pretty interesting, thanks for the link Blashyrk, Wed, 9th Mar 2011
This is a great theory, I have delved into the inklings that biological life may have been carried by cellestial vector objects moving through space that entered the earth's atmosphere and brought the micro-orgnisms into the "perfect" breeding grounds for life to evolve. However, the theory that instead, these vector quantity objects brought the chemical compound building blocks necessary for life to form is a much better one. It makes sense that these copounds came form the chemical make-up of these bodies rather than taking a wild ride on the surface through space where they would indeed be inhibited on frozen biological matter, they would also be exposed to all of the dangerous and destructive radiation, of which there would have been much higher volumes in the earlier stages of the universe. But then that still leaves us with the question: why did these chemical compounds form in these asteroids and other cellestial bodies and just what were the probabillities that these exact samples were to collide with this planet out of all of the satellites in the universe, and how do we know that the same thing hasn't happened elsewhere in this enigmantic cosmos and how many more times could this happen. In other words, this is an extraordinary case in which there is a lot of entorpic circumsances to consider. However, one thing is certain, and that is that entropy tends to "centre" or "even" out uniformly the more that it occurrs and that highly unlikely circumsances will happen no matter the odds. so, if this highly improbable event has occurred once, then it will tend, over time, to uniformly occurr. But on that note, there is yet another problem. That is that these occurances must occur over the entire expanse of the universe in order to be uniformly present. So, for all that we know, we could have neightbours in our visible space, or to get you thinking, in farther reachres of the universe which we cannot see but, those intelligent life forms are very familliar with or quite the opposite, in which life is new and still in the basic protein stages or even not yet there. The basic point of this all, is that yes this could in fact be the way that life was brought to this planet, but it still cannot answer why or how many more times on how many different planets this has occurred on, and even more inportant than all of that, is the question; "Why?". kvantovoi kvark, Mon, 28th Mar 2011
One could, of course, claim that the entire Earth was built out of meteorites... and thus, the planet forming meteorites in the solar system necessarily brought the building blocks of life.
What is the chemical makeup of water from a geyser or hot spring?
I can see that the question is opening up into two threads: (a) how did life begin (anywhere) and (b) did it begin on earth or somewhere else?
Researchers wanted to determine if amino acids embedded in comets could survive an impact with the Earth, so they fired a 'snowball' laced with them at very high velocity into a target. They found that the amino acids readily linked up to form peptides with considerably more than three components. If you (or anyone) wishes I shall try to locate the relevant paper. Ophiolite, Wed, 23rd Oct 2013
We are all star dust..
If you have a liposome, is it already selectively permeable, or what would also be required? Can it trap things? Or does it depend on what's already inside it? cheryl j, Thu, 7th Nov 2013
The how is getting Found, but the start is always a WHY..
No, it's a how. If you mix A and B and the product C has lower energy or more entropy, you will eventually end up with C.