We were one of two groups that published articles in the March 28th issue of Nature on the formation of amino acids in ice. The other letter in Nature (Munoz-Caro et al) was written by scientists from four research groups in Europe. Our results are generally quite similar. We both report having formed amino acids by shining ultraviolet light on ice at interstellar temperatures, and we agree that this suggests that some of the amino acids seen in meteorities must have formed in dense molecular clouds out in deep space.
The differences between these papers lie in the details of the amounts and types of amino acids that were formed. They saw many more amino acids, and more of them, even though we used a more sensitive technique. Actually, its not surprising at all considering that we used different starting materials at different concentrations. We used ices that were dilute, mostly water with only a few % of carbon containing molecules. They started with an ice that had more carbon molecules than water.
This makes a big difference, especially for the bigger amino acids. This is because the starting molecules have to get together to make the amino acids, and the bigger the amino acid the more of them that must come together. Since there is a lot of water in our mixture it's hard for them to get together to make a big molecule, but we still make the small ones.
Who's right, us or them? We both are, of course. We think our starting concentration is most representative of what is out there in deep space, and we back it up by referring to specific astronomical objects in our paper. In fact, we think that it's good that we don't make all of those other amino acids. After all, many of the big amino acids are not seen in meteorites, and at those concentrations, they would have been. The few that we make are the same ones in meteorites that carry deuterium, so they are the ones that seem like they come from space.