Red slime mat made up of an extremophile bacteria in hot springs in Mono Lake, California use arsenic rather than water to carry energy during photosynthesis, U.S. Geological Survey researchers have found.

By analyzing the genetic material of the microbe, the researchers have determined that this is a primitive process, going back at least three billion years. That could mean that arsenic-based photosynthesis predates the oxygen-producing variety that enables life as we know it.