Our origins are still up in the air

First, there was alcohol. Then came hair bleach. Now, at last, we've found a tiny bit of oxygen. This is not CSI: Stringfellows. This is the effort to understand the origins of life on earth.

We have traced the history of the universe back to the Big Bang, so you might think that there's little left to discover. You'd be wrong. Even last month's breakthrough discovery - our first glimpse of oxygen molecules outside earth's atmosphere - has left astronomers puzzled: there's a lot less of it than there should be.

This matters because it could help tie together the threads of where we came from. The most abundant elements in the universe are hydrogen and helium. Our theories suggest that much of these elements should have been created in the firestorm after the Big Bang. They match our observations of how abundant these elements are in outer space almost exactly, providing support for our story of the beginning of everything.

Oxygen is the third most abundant element. There are plenty of single oxygen atoms around but there should also be a lot of the molecular variety, consisting of two atoms joined together. On 1 August, the European Space Agency announced that Herschel, its space-based telescope, had found signatures of molecular oxygen in the Orion nebula.

This is the first reliable sighting but there is much less of it than the scientists expected. That poses a problem for our theories about how earth got its water - and thus how life started.

Researchers think that earth was formed dry and water arrived on meteorites, which implies that the water formed in space. The chemistry of this involves a couple of steps. First, hydrogen binds to oxygen molecules to form hydrogen peroxide - better known as hair bleach. Then, more hydrogen and oxygen molecules come along and cannibalise the hydrogen peroxide to form water molecules.

For this to happen, all these precursors should exist in space, which is why astronomers were so excited at the beginning of July when they spotted space-borne hydrogen peroxide for the first time. It wasn't too far away: about 400 light years, to be precise, close to the star
Rho Ophiuchi.

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The apparent scarcity of molecular oxygen, although it's better than nothing, shows that there is still a piece missing from the puzzle. There is simply not enough available to account comfortably for the rest of the water-forming process.

At least we know that the raw ingredients for human life are all out there. Hydrogen, oxygen and carbon atoms make up more than 90 per cent of your body weight and space contains them in remarkable abundance in a popular form. The gas cloud Sagittarius B2 contains roughly a billion billion billion litres of alcohol at 200 per cent proof - more alcohol than human beings have distilled in their history.

Before you head off in search of a space party, however, you should know that it is very hard to tap. The alcoholic gas is so sparsely distributed that filling a single glass would entail trawling a volume roughly the size of earth. Then again, like the newly discovered oxygen, it's better than nothing.

Tags:Science