- April 20, 2026
- By Georgia Jiang
Scientists analyzing volcanic rocks from island chains discovered chemical fingerprints dating back 4.5 billion years—evidence that parts of Earth's deep interior remained virtually untouched since our planet's earliest days, long before the cataclysmic impact that formed the moon.
The findings, published in the journal Geochimica et Cosmochimica Acta, challenge popular theories about both the source of these ancient signatures and the violence of the moon-forming collision that scientists believe reshaped Earth roughly 100 million years after its formation.
“We’re seeing chemical signatures that could have only formed really early in Earth history showing up in these comparatively young volcanic rocks,” said the study’s lead author, Val Finlayson, an assistant research scientist in the Department of Geological, Environmental, and Planetary Sciences at the University of Maryland. “It’s pretty wild that this differentiation process, or how molten rocks separate into chemically distinct layers as they cool and crystallize, may have somehow stayed preserved throughout the entirety of Earth’s history.”
The research team analyzed basalt samples from three island chains in the Pacific Ocean. The key isotope, tungsten-182, was created by radioactive decay during Earth’s first 50 to 60 million years, when a parent element called hafnium-182 was still present on the planet. Once hafnium decayed away, new tungsten-182 could not form.
These ancient chemical signatures are thought to originate from approximately 2,800 kilometers (1,739 miles) below Earth’s surface, where the base of the mantle meets the Earth’s liquid outer core. Volcanic hot spots like Hawaii and Iceland tap into this deep reservoir.
Finlayson noted that the team’s findings have implications for understanding how Earth’s moon formed. The prevailing theory suggests a Mars-sized object called Theia collided with an early version of Earth around 100-150 million years after the solar system’s formation. Many models depict this as a catastrophic event that completely vaporized and remixed Earth’s interior.
But if signatures from even earlier times survived into the present day, the impact may not have been as destructive as previously thought.