How did life start on Earth? Science still has no definitive answer. But in the 1950s, a pair of chemists mixed a stew of poisonous gases, like you'd find at a volcano. They zapped it with electricity, mimicking lightning. And they found that they'd created a few amino acids. All life on Earth relies on these compounds to make proteins.

　　In 2007 researchers at Scripps Institute of Oceanography found sealed samples from those half-century old experiments. They re-examined the contents with today's better equipment, like liquid chromatography and mass spectrometers, and found that the electrified volcano's breath produced 23 different amino acids. The work appears online in the early edition of the Proceedings of the National Academy of Sciences.

　　The finding could mean that various building blocks of life were common in pools of water on the surface of the early Earth. What's more, the amino acids are similar to those found on certain types of meteorites, which suggests that the basic constituents of life could be widespread in the universe.

　　But how those oases of amino acids started to come together and form life? Well, the origin of life as we know it remains a mystery.