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New Delhi: A team of scientists funded by NASA has explored why the reliance of life on molybdenum predates its abundance in the ocean. Three billion years ago, life relied on molybdenum, which was scarce at that time. Molybdenum helps speed up biochemical reactions within cells, and is a component of essential enzymes. The metal is important for individual organisms, as well as biogeochemical cycles that affect the entire planet, such as the nitrogen cycle. Without molybdenum, the reactions could still occur, but not at a pace sufficient to sustain life.

Timeline of history on Earth. (NASA).

Geological evidence indicates that only trace amounts of molybdenum were present in the oceans of Earth billions of years ago. About 2.45 billion years ago, with the advent of photosynthesis, there was a dramatic surge in atmospheric oxygen, known as the Great Oxidation Event. This surge had a profound effect on the evolution of life on Earth, which previous research suggesting that the increase of molybdenum in the environment around the same time paved the way for the emergence of complex life. Scientists explored if primitive life used tungsten, a chemical twin of molybdenum, at a time when the latter was scarce in the oceans of Earth.

Molybdenum was first choice for life

Tungsten behaves similar to molybdenum in cells, and is used by some organisms today, that live in extreme environments. Scientists had also previously suggested that life may have evolved to first use tungsten, then switched to molybdenum when its abundance increased. The new research suggests that this was not necessarily the case, that indicates that primitive life used both metals. The study indicates that even with a diversity of useful available in environments such as hydrothermal vents, molybdenum was the first choice for a metal catalyst. A paper describing the research has been published in Nature Communications.