Extraterrestrial Origins Of Life on Earth

The trouble is that amino acids don't often survive impact. When Bada et al investigated this by studying the Tunguska impact site for alpha-amino-isobutyric acid - which is common in interstellar space but extremely rare on earth - they didn't find any. (Here, page 12 - couldn't find a link to the research itself, sorry).Some amino acids created in space probably do reach the Earth but it is extremely unlikely that they ever did so in anywhere near the concentrations that would be necessary to explain the origin of life.Edited by Mr Jack, : Correction

The link I gave in the post has some of it. I've just been studying this as part of an OU course. We can calculate reasonably well the mass of material that fell on the earth around 4.5-4 Ga ago, although the quantities of amino acids contained in this material is more open, it's certainly not large (or we'd be detecting it in modern meteorites in large amounts), and there is good reason to believe most of it is destroyed before reaching the Earth. The oceans on the other hand, are very large, sticking the numbers (some of them guessed at) together you find that the chances of just two amino acids coming into contact mean that it would happen once every 10,000 to 100,000 years. That's simply not enough to account for the origin of life.I find hydrothermal vents a much more likely source of organic compounds needed to form life; bubble theory also seems interesting. Aye, that's me.

Interstellar dust does not fall in sufficient quantities to create a high enough concentration to acount for the origin of life.

I'm far from convinced there is a problem of chirality. Even if there is, I'm not sure how this is supposed to solve it. The most biased interstellar creation scenarios I know of only create a 60/40 bias. Compare that to selective binding to crystal faces which get a 90/10 bias.