To give you the background, glycolaldehyde is a fairly simple hydrocarbon molecule, and arguably the simplest known sugar (a “diose”). I say arguably, because if we’re to be strict about things it can’t readily cyclise, and the formal definition of a monosaccharide requires at least three carbons. But leaving aside the debate on its sugary status, glycolaldehyde is a molecule not unlike certain compounds you might find in your shampoos, pints of beer or (if you’re in the UK) sprinkle onto your chips.
Interestingly, it’s actually been known in space since 2000, discovered in our old friend the Sagittarius B2 complex using radio telescopes (specifically, the NRAO 12m telescope). Beltran et al, however, have found this chemical in a hot molecular core named G31.41+0.31. Molecular cores are dense knots of gas and dust which are in the process of condensing into stars and possibly planets. G31.41+0.31, from the sound of it, is probably closer to being a protostar. This work, then, makes the prospects of life on any future planets around it seem rather favourble.
One thing that puzzles me is exactly how they propose that glycolaldehyde could be a precursor to ribose. They talk about reacting glycolaldehyde with propenal to make ribose, but as far as I can see (unless I’m being stupid) that just won’t make ribose. It’s two hydroxyl groups short, and they make no suggestion as to where those errant atoms may come from.
EDIT– I’ve just been informed, thanks to an anonymous organic chemist, that these hydroxyl groups could be acquired from water molecules. This is probably the most feasible explanation — water, if I remember correctly, is the third most common molecule in the entire Universe (after dihydrogen and carbon monoxide).
Alternatively, reacting it with glyeraldehyde (which is the actual simplest sugar) would be the simplest synthesis route. This, however, would still leave the puzzle of where the glyceraldehyde would come from, which is a matter I don’t intend to speculate on…
Again though, all of that aside, I like the way this group present their work. On the formation of glycolaldehyde, they first dismiss radical mechanisms as too slow (seemingly a recurring theme in astrochemistry at the moment), before suggesting surface reactions as the main formation route. Molecules adsorb onto cosmic dust grains, react, and then desorb as the final molecule. Simply put, this seems to be the best way to explain the amount of glycolaldehyde they’ve observed in G31.41+0.31! It could also explain where those missing hydroxy groups came from — they could easily be stolen from a grain surface.
The thing is though, if ribose could conceivably form this way (and I’m sure there are people out there looking for it even as I type this) then how about other similar molecules? Ribose is a furanose sugar — essentially based on the structure of furan. So how about other furan derivatives?
Well, two other furan derivatives are fructose and furaneol — the two compounds which give strawberries their sweetness and taste, respectively. I conclude, somewhat whimsically, that hot molecular cores probably taste like strawberries.
Hey, given the wealth of molecules in the ISM, there’s no reason why it’s less likely than ribose!
M.T. Beltran, C. Codella, S. Viti, R. Neri, R. Cesaroni (2008). First detection of glycolaldehyde outside the Galactic Center Astrophysical Journal Letters (preprint) arXiv:0811.3821v1