To get life, you first need organic molecules, and the easiest way to get those is from the compound methanol. Now it seems there are very specific conditions needed to create methanol and, ultimately, life... and most stars don't have them.
The organic molecules that are the basis for life here on Earth — and, presumably, elsewhere in the cosmos — aren't all that hard to make. All you need is some carbon, some oxygen, and some hydrogen to get started. The real trick is bringing those elements together and keeping them together long enough to start forming complex bonds. We have observed lots of carbon monoxide in star-forming clouds. All that's needed is some hydrogen from those newborn stars to enter the mix and organic molecules can start forming.
The easiest way for these three elements to start combining is on the surface of tiny dust grains, which are found all over the place around new stars. The idea is that carbon monoxide found on the surface of these grains can react with hydrogen at low temperatures to form methanol, which has the chemical formula CH3OH. Methanol can then serve as the basis for the formation of far more complex organic molecules and, possible, the eventual development of life itself.
Until now, we haven't really had a good handle on how much methanol there is in the galaxy, or where it's located. Researchers at the New York Center for Astrobiology at Rensselaer Polytechnic Institute set out to fix that, and they got some striking results. The amount of methanol around a new star varies wildly, from barely any at all to as much as 30% of the ice orbiting a star.
The researchers argue that there's a sweet spot in terms of the physical conditions needed to create lots of methanol. Molecules need to reach the dust grains at just the right speed so that there's a steady enough supply for the consistent formation of methanol, but if the molecules pile onto the dust grains too fast they can get trapped there without ever forming more complex molecules.
Lead researcher Douglas Whittet explains:
"If the carbon monoxide molecules build up too quickly on the surfaces of the dust grains, they don't get the opportunity to react and form more complex molecules. Instead, the molecules get buried in the ices and add up to a lot of dead weight. If the buildup is too slow, the opportunities for reaction are also much lower."
It's possible to get life without this initial supply of methanol, but the road to complex organic molecules becomes a lot trickier. Basically, solar systems that are in this methanol-producing sweet spot have a huge advantage in terms of the raw materials needed for life.
Even then, there may not be a direct linear relationship between the amount of methanol in a solar system and the chances of life forming — it's possible that only a relatively small amount is needed to get organic molecules forming, and too much methanol is (possibly quite literally) overkill. In fact, there's at least one solar system that did just fine in the life-forming department without a ton of methanol: our own.
Analysis of comets dating back to the formation of our solar system shows there wasn't a huge amount of methanol available. As Douglas Whittet explains, we may well have had to overcome some very early bad luck to get where we are today:
"This means that our solar system wasn't particularly lucky and didn't have the large amounts of methanol that we see around some other stars in the galaxy. But, it was obviously enough for us to be here."
So what if we had been lucky, and our solar system had been just bursting with methanol? Whittet thinks such solar systems are out there, and it's conceivable that the biological results are even more spectacular than all the life found in our own solar system. What that means, exactly, is something we're probably going to have to leave to our imaginations for the time being, but it's a seriously intriguing thought.