View Full Version : Space Chemistry

2013-Jul-01, 11:44 AM
I came across this piece in Nature (http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.1692.html) (Chemistry) which seems to add a tidbit to the sources of complex molecules in planetary disks. To wit:

Understanding the abundances of molecules in dense interstellar clouds requires knowledge of the rates of gas-phase reactions between uncharged species. However, because of the low temperatures within these clouds, reactions with an activation barrier were considered too slow to play an important role. Here we show that, despite the presence of a barrier, the rate coefficient for the reaction between the hydroxyl radical (OH) and methanol—one of the most abundant organic molecules in space—is almost two orders of magnitude larger at 63 K than previously measured at ∼200 K. We also observe the formation of the methoxy radical product, which was recently detected in space. These results are interpreted by the formation of a hydrogen-bonded complex that is sufficiently long-lived to undergo quantum-mechanical tunnelling to form products. We postulate that this tunnelling mechanism for the oxidation of organic molecules by OH is widespread in low-temperature interstellar environments.

Apparently they were able to form methoxy in a low temp chamber mixing OH and methanol, and show that quantum tunneling can be far more active in low temp environs, making space-based chemistry a bit more potent a source for complex molecules than previously estimated. That is, the lack of sufficient energy is overcome by quantum effects.

The chemistry of planetary systems increasingly seems to depend on a complete web of sources, many formed off-planet and deposited by bombardment, meaning that deriving the mechanisms for abiogenesis will depend on understanding not just surface conditions and local chemistry, but also on external contributions, and perhaps even iterated inter-body and "cloud"-planetary exchanges. Early planetary disks may act as life factories in a systemic fashion.

2013-Jul-01, 06:25 PM
Perhaps we have much to learn about the chemical processes that take place at low temperatures and densities which may have profound effects on our understanding of galaxies, and the formation of stars and planets. There was a interesting recent paper "A snowflake's chance in heaven" (http://arxiv.org/abs/1306.5587) that suggests a mechanism through which stable grains of frozen hydrogen can form. Currently theorists assume that it is not possible for solid hydrogen to exist in the ISM. Much of our understanding is based on extrapolations rather than experiment because such experiments are difficult.