Molybdenum: The Rare Metal That Powered Life 3 Billion Years Ago

Three billion years ago, Earth’s oceans were basically empty when it came to metals. But microscopic life found a way forward with molybdenum, a rare metal that was incredibly hard to find back then. Scientists have discovered that this metal became essential to early life.

The discovery, detailed in a study published in Nature Communications, opens a window into the biochemical strategies that powered the planet’s earliest organisms.

So When Did Life Actually Start Using Molybdenum?

Molybdenum sits at the catalytic center of enzymes that drive major biochemical reactions, particularly those involving carbon, nitrogen, and sulfur cycles.

“Asking when life began using molybdenum is really asking when some of the most consequential metabolic strategies became possible.” Without this metal, vital reactions in living cells would proceed far too slowly to sustain life as we know it.

Betül Kaçar, University of Wisconsin-Madison

Previous theories suggested early life might have relied on tungsten until molybdenum became more abundant. However, the research reveals that both molybdenum and tungsten-using enzyme systems trace back to the Archean period.

“Our work shows that early life likely worked with both metals rather than following a ‘tungsten first, molybdenum later’ story,” Kaçar adds.

The study’s molecular dating pushes molybdenum’s use back to the Eoarchean to Mesoarchean era, around 3.7 to 3.1 billion years ago, far earlier than previously thought. This finding suggests that molybdenum was integral to early life, not a later addition after the Great Oxidation Event.

The Underground Metal Markets

Microbes found molybdenum in extreme environments like hydrothermal vents at the seafloor, which provided trace metals including iron, zinc, copper, nickel, manganese, vanadium, molybdenum, cobalt, and tungsten. These deep-ocean chimneys may have served as crucial supply depots for ancient microbial life.

“Even if Archean seawater held little dissolved molybdenum overall, localized systems such as hydrothermal vents could still have supplied usable amounts of molybdenum and other metals.”

Betül Kaçar

Molybdenum’s scarcity didn’t diminish its appeal to early organisms. Instead, the metal’s unique catalytic properties made it worth the effort to acquire.

“Molybdenum may have been worth ‘choosing’ because it enables catalysis across a broad range of substrates and redox conditions. In other words, scarcity did not make molybdenum unimportant; its catalytic advantages may have made it worth evolving ways to acquire and use.”

Betül Kaçar

Rethinking the Search for Alien Life

By demonstrating how early life worked with scarce resources and made strategic choices about which metals to exploit, the study reshapes the search for extraterrestrial life. A checklist of “Earth-like conditions” may miss far more than it finds. Insights from space exploration tech like the ESA Space Rider highlight advanced missions probing other worlds.

“Our NASA ICAR shows that mapping the evolutionary history of bio-essential elements on Earth can help us predict what life on other worlds might use, and that different abiotic inventories could lead to different biological element choices.”

Betül Kaçar

On a planet with different oxygenation history or a different suite of available metals, life might make entirely different biochemical choices than it did on Earth.

“Life detection should be metal-aware, redox-aware, and evolution-aware. We should look not just for ‘Earth-like life now,’ but for biochemical strategies that would make sense on a planet with a different history of oxygenation and metal availability.”

Betül Kaçar