Bugs and stardust

An "extinction" curve is basically a plot showing what's missing from the spectrum of the galaxy. Since stars are "black bodies", they output across the whole electromagnetic spectrum, any bits that are missing from the spectrum is because there is something between us and the source absorbing/scattering the radiation at that wavelength.

There is a particular bit missing at 2175 Å that's been typically explained by suggesting many small graphite spheres absorbing and scattering the radiation. Now researchers at the Cardiff centre for Astrobiology are saying that this band could be better explained by the organic molecules life of earth is composed of.

The experiment is wonderfully straightforward: they simply dissolved grass, algae etc. in cyclohexane and measuring the extinction curve you get from that. The result seems to agree pretty well with the mysterious peak seen in the spectrum. It's one of those experiments that is so simple that you wonder why someone else didn't do it before now?

If this is really what's out there, then that leaves the question of how it got there. That prebiotic organics show up in space isn't exactly unknown. However, the paper suggests that this really might be the remains of microbes growing in the "liquid interiors of primordial comets" that are "distributed widely throughout the galaxy". I don't know how reasonable that speculation is, but it's certainly one that won't be accepted until we actually get hold of a comet, crack it open, and find bugs living inside.