Phosphorus is an essential element for life as we know it. But how it arrived on the early Earth is something of a mystery. Astronomers have now traced the journey of phosphorus from star-forming regions to comets using the combined powers of ALMA and the European Space Agency’s probe Rosetta. Their research shows where molecules containing phosphorus form, how this element is carried in comets, and how a particular molecule may have played a crucial role in starting life on Earth.