Ancient microbes appear to have used molybdenum as far back as 3.7 billion years ago, despite the metal being scarce in Earth’s early oceans.
Scientists funded by NASA have found that organisms living on Earth more than 3 billion years ago were already using molybdenum, even though the metal was extremely rare in the environment at that time. The research, in Nature Communications, is the first study to show that ancient life depended on molybdenum this early in Earth’s history.
Today, molybdenum plays a key role inside cells by helping important biochemical reactions happen faster. It forms part of essential enzymes that drive several major biological processes in living organisms. These reactions matter not only for individual forms of life, but also for planet-scale biogeochemical cycles, including the nitrogen cycle. Without molybdenum, the same reactions could still occur naturally, but far too slowly to support life.
“Molybdenum sits at the catalytic center of enzymes that run major carbon, nitrogen, and sulfur reactions,” explained Betül Kaçar, head of the Kaçar Lab at the University of Wisconsin Madison and senior author on the study. Kaçar leads MUSE, a NASA Interdisciplinary Consortia for Astrobiology Research (ICAR) at UW Madison.
“Asking when life began using molybdenum is really asking when some of the most consequential metabolic strategies became possible,” said Kaçar.
Molybdenum through history
Molybdenum is fairly widespread in the environment today, so life no longer faces a major shortage of it. Early Earth was very different.
Geological records indicate that Earth’s oceans contained only tiny amounts of molybdenum billions of years ago. Its availability rose around the time microbes began using photosynthesis, a shift that eventually caused a large increase in atmospheric oxygen (roughly 2.45 billion years ago). Known as the Great Oxidation Event, this transformation deeply influenced the evolution of life. An earlier NASA study even proposed that the increase in environmental molybdenum during this period may have been important for the emergence of complex life.
That left a major question: when did organisms first begin using molybdenum?
Since the metal was so limited on ancient Earth, astrobiologists have considered whether early life may have relied on other metals to accelerate essential reactions. Tungsten, for example, behaves in similar ways inside cells and is still used by some organisms that live in extreme environments. One idea had been that life first depended on tungsten, then later shifted toward molybdenum as it became more available. The new research suggests the story was not that simple.
To investigate, the team compiled existing evidence on how much molybdenum was available through time and reconstructed the history of its use across the tree of life. Their results show that even when molybdenum was rare, ancient microbes still managed to use it. The same pattern applies to tungsten.
“Our work shows that both molybdenum- and tungsten-using enzyme systems have Archean roots, which suggests that early life likely worked with both metals rather than following a simple “tungsten first, molybdenum later” story,” said Kaçar. “We argue that molybdenum use is far older than many models assumed, with molecular dating placing molybdenum utilization back into the Eoarchean to Mesoarchean, roughly 3.7–3.1 billion years ago, well before the Great Oxidation Event.”
Accessing molybdenum
Earlier research from the MUSE ICAR, published in 2024, pointed to specific environments where early organisms may have obtained molybdenum and other rare metals deep beneath the ocean. Hydrothermal vents on the seafloor can release trace metals such as iron, zinc, copper, nickel, manganese, vanadium, molybdenum, cobalt, and tungsten.
“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,” said Kaçar.
The new findings indicate that, even with many useful metals available, molybdenum was among the early metals life selected for catalytic chemistry.
“Molybdenum may have been worth “choosing” because it enables catalysis across a broad range of substrates and redox conditions,” said Kaçar. “In other words, scarcity did not make molybdenum unimportant; its catalytic advantages may have made it worth evolving ways to acquire and use.”
The work shows that life can evolve ways to exploit useful elements even when they are scarce. It also suggests that the search for life beyond Earth should remain open to biochemical possibilities that may not match what scientists expect from modern Earth alone.
Bio-essential elements, search for life in universe
Looking for life elsewhere in the universe is not simply a matter of checking whether another world resembles Earth today. By studying Earth’s own past and the long evolution of life, astrobiologists can examine times when our planet looked very different from the one we know now. That broader perspective helps scientists better understand what kinds of worlds may be able to support life as we know it.
“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,” said Kaçar. “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.”
Reference: “Biological use of molybdenum and tungsten stems back to 3.4 billion years ago” by Aya S. Klos, Morgan S. Sobol, Joanne S. Boden, Eva E. Stüeken, Rika E. Anderson, Kurt O. Konhauser and Betül Kaçar, 5 May 2026, Nature Communications.
DOI: 10.1038/s41467-026-72133-0
Funding support from a NASA Astrobiology Program Grant [80NSSC18KO829] (REA) and a NERC Frontiers grant (NE/V010824/1) (J.S.B. and E.E.S.)
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