Scientists have detected additional amino acids in the original samples from the classic Miller-Urey experiment: a mixture of gases and water that Miller thought were present on early Earth was heated and zapped with electricity to mimic lightning. This created five identifiable amino acids.

But one of the two lesser-know experimental setups — a volcanic apparatus adding steam — created 22 amino acids that could be positively identified, and could offer the best clue to how life on Earth began some 4 billion years ago.