Planetary sources of bio-essential nutrients on a prebiotic world.

Multiple bio-essential elements such as nitrogen and phosphorus are found in all forms of life discovered thus far. In addition to these major elements, many transition metals have been proposed as crucial components for prebiotic and early cellular processes. These elements must, therefore, have been available during the origin of life; however, the processes that mobilized them on the prebiotic Earth likely differed from today. We provide a review and discussion on planetary processes that influenced the availability of bio-essential elements on early Earth and propose the most likely environments to host key prebiotic reactions and perhaps primitive life, based on their supply of nitrogen, phosphorus and transition metals. In particular, terrestrial acidic hot spring systems and deep-sea hydrothermal vents may have created ideal conditions through abiotic nitrogen reduction, dissolution of reactive phosphorus species and leaching of siderophilic transition metals from igneous bedrocks. This concept has implications far beyond Hadean Earth, as similar geothermal systems once existed on the surface of Noachian Mars, providing a comparable suite of elements, suggesting that crucial steps towards an independent origin of life may have unfolded on Mars and perhaps other terrestrial planets.This article is part of the theme issue 'Origins of life: the possible and the actual'.