For more than 150 years, scientists have known that the most basic building blocks of life -- chains of amino acid molecules and the proteins they form -- almost always have the unusual characteristic of being overwhelmingly "left-handed." The molecules, of course, have no hands, but they are almost all asymmetrical in a way that parallels left-handedness.

But research into the question has picked up in recent years, focusing on a 200-pound chunk of rock found 40 years ago in Murchison, Australia. A meteorite that broke off an asteroid long ago, it brought to Earth a rich collection of carbon-based material from far away in the solar system.