Iron is integral to the development of life on Earth and the possibility of life on other planets

Iron is an essential nutrient that almost all life needs to grow and thrive. The importance of iron dates back to the formation of planet Earth, where the amount of iron in the rocky mantle of the Earth was “fixed” by the conditions in which the planet formed and had major ramifications on development of life. Now, scientists at the University of Oxford have uncovered the likely mechanisms by which iron influenced the development of complex lifeforms, which can also be used to understand how likely (or unlikely) advanced lifeforms are. ) on other planets. The book was published today in PNAS.

“The initial amount of iron in Earth’s rocks is ‘defined’ by planetary accretion conditions, during which Earth’s metallic core separated from its rocky mantle,” says co-author Jon Wade. , associate professor of planetary materials in the Department of Earth. Science, University of Oxford. “Too little iron in the rocky part of the planet, like the planet Mercury, and life is unlikely. Too much, like Mars, and water may be difficult to keep on the surface for evolutionarily relevant periods of complex life.

Initially, the iron conditions on Earth would have been optimal for ensuring surface water retention. Iron would also have been soluble in seawater, making it readily available to give simple life forms a boost in development. However, oxygen levels on Earth began to rise about 2.4 billion years ago (known as the “great oxygenation event”). An increase in oxygen created a reaction with the iron, which made it insoluble. Gigatons of iron fell from sea water, where it was much less available to developing life forms.

“Life had to find new ways to get the iron it needs,” says co-author Hal Drakesmith, professor of iron biology at the MRC Weatherall Institute of Molecular Medicine, University of Oxford. “For example, infection, symbiosis, and multicellularity are behaviors that allow life to more efficiently capture and utilize this rare but vital nutrient. Embracing such characteristics would have propelled early life forms to become increasingly complex, evolving into what we see around us today.”

The need for iron as a driving force in evolution, and the consequent development of a complex organism capable of acquiring scarcely available iron, may be rare or random occurrences. This has implications for the likelihood of complex life forms being present on other planets.

“It’s unclear how common intelligent life is in the Universe,” says Professor Drakesmith. “Our concepts imply that the conditions to support the initiation of simple lifeforms are not sufficient to ensure the subsequent evolution of complex lifeforms as well. Further selection by severe environmental changes may be required, for example, how life on Earth had to find a new way to access iron. Such planetary-scale temporal shifts may be rare or random, meaning the likelihood of intelligent life may also be low.”

However, knowing now how important iron is in the development of life can help in the search for suitable planets that can develop life forms. By assessing the amount of iron in the mantle of exoplanets, it may now be possible to narrow down the search for exoplanets capable of supporting life.