NASA-supported researchers have shown that ultraviolet (UV) light could have played an important role in recycling biological phosphorus on the early Earth. Previously, many scientists hypothesized that life would have experienced a ‘phosphorus famine” before the Great Oxidation Event that altered Earth’s atmosphere some 2.35 billion years ago. Theories suggested that a lack of access to phosphorus during this time would have limited the primary productivity in Earth’s oceans.

Phosphorus (P) is an essential element for life as we know it and, on the Earth today, P can be difficult for life to access in many environments. For marine life in the oceans of Earth, biological recycling of P from dead organisms is an important source of this vital element. However, many of the organisms involved in the recycling of P require oxygen to carry out this process, which is much easier to access when there are high concentrations in the atmosphere.

The new study shows that UV light can help to break down organic phosphorus (P that is bound up in the types of molecules produced by life, e.g. molecules that contain carbon). The study was carried out in conditions similar to the oceans of the Archean Earth, and the results suggest that UV-mediated recycling of organic phosphorus could have provided more than enough P to support a flourishing biosphere in Earth’s early oceans.

The study, “Archean phosphorus recycling facilitated by ultraviolet radiation,” was published in the Proceedings of the National Academy of Science.