Associate Professor Christopher Junium has demonstrated that ammonium—an odiferous chemical compound, often used in fertilizer—was a vital source of nitrogen for early life on Earth. Working with colleagues from the University of St. Andrews in Scotland and Royal Holloway in London, he has discovered chemical signatures of ammonium in rare 2.7 billion-year-old rock. “As long as other nutrients such as iron and phosphorous were present, ammonium in ancient oceans may have helped stimulate the production of oxygen some 400 million years before its appearance in the atmosphere,” he says.