Geologists have made a landmark discovery off the coast of Mayotte in the Indian Ocean, identifying chemical traces of Earth’s primordial magma ocean within lava from a recently formed underwater volcano. The volcano, named Fani Maoré, emerged following a series of seismic events in 2018, providing researchers with a rare window into the planet's earliest history.
A 4.5 Billion-Year-Old Chemical Signature
According to a study published in the journal Nature, the lava erupted by Fani Maoré contains specific neodymium isotope ratios that date back to the Hadean eon. Scientists believe that shortly after Earth's formation, a massive collision with a Mars-sized object created a global magma ocean. As this molten rock cooled and crystallized over millions of years, it formed the planet's mantle and early crust.
Using ultra-precise analytical techniques, researchers from the French National Centre for Scientific Research (CNRS) and the University of Cambridge identified a higher ratio of neodymium-142 to neodymium-144 in the Fani Maoré samples compared to surrounding volcanic rock. This signature indicates the presence of bridgmanite, a mineral thought to be among the first to crystallize from the primordial melt.
Challenging Geological Assumptions
For decades, the prevailing scientific theory held that the steady churning of Earth’s mantle over 4 billion years had effectively erased the chemical signatures of the planet's infancy. However, the presence of these isotopes suggests that pockets of the ancient mantle have remained unmixed and preserved deep underground.
"This is going to change a lot of things in earth science," said Catherine Chauvel of the CNRS. "We now have proof that materials from the very beginning of Earth’s history still exist in sufficient quantities to be sampled." The discovery allows scientists to experimentally reconstruct how the primordial ocean solidified and created the chemical diversity seen in the mantle today.
