4.404-billion-year-old Jack Hills zircon matches Moon’s final crystallization, 2025 study finds
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A zircon grain from Australia’s Jack Hills has been dated to 4.404 billion years, aligning with the Moon’s final solidification, according to a 2025 study. The finding reinforces evidence for a cool early Earth with liquid water billions of years earlier than previously thought.
The Jack Hills Zircon
First identified by Simon Wilde and colleagues in 2001, the zircon was dated using uranium-lead geochronology. The age was confirmed in 2014 by John Valley’s team at the University of Wisconsin-Madison with atom-probe tomography. The crystal measures roughly 400 micrometres across and glows blue under an electron beam. Its durability allowed it to survive billions of years of erosion and heating, preserving its initial crystallization record.
The Moon’s Final Crystallization
A 2025 study determined the Moon finished solidifying approximately 4.404 billion years ago, coinciding with the zircon’s age. The Moon formed from debris after a Mars-sized body struck the early Earth around 4.5 billion years ago. While the impact was quick, the Moon’s crystallization was a prolonged process. The alignment suggests the zircon crystallized after the impact in an environment cool enough for liquid water.
Early Earth and the Hadean Eon
Oxygen isotopes in the zircon indicate formation in the presence of liquid water at low temperatures, supporting a cool early Earth. This challenges the traditional view of the Hadean eon as a molten, hostile period. Trace element evidence from Jack Hills zircons suggests crust and surface water existed within 100–200 million years of the planet’s formation. Some researchers argue this extends the earliest plausible window for life on Earth.
What's Next
Future studies may examine other Jack Hills zircons for similar alignment with lunar chronology. It remains unclear whether this coincidence carries implications for the evolution of life or merely refines the timeline of planetary cooling.
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4.404-billion-year-old Jack Hills zircon matches Moon’s final crystallization, 2025 study finds
