Moon dust, meteorites and more: How Earth got its water, scientists rewrite the story

NASA Study Finds Earth’s Water Mostly Formed, Not Delivered (Image: Canva)

A new NASA study using Apollo Moon soil samples suggests most of Earth’s water came from the planet’s original formation, not meteorite impacts. By analysing oxygen isotopes in lunar regolith, scientists found meteorites contributed only a small share. The findings also help explain water on the Moon and support future Artemis missions, offering deeper insight into the early solar system and planetary formation.

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Most of Earth’s water likely formed during planetary construction, scientists report. A NASA study using Moon samples sheds light on water origins. The research examines ancient meteorite impacts within the Earth-Moon system. Findings suggest meteorites contributed only a limited share of water.

The study was published Tuesday in the Proceedings of the National Academy of Sciences. It was led by Tony Gargano based at NASA facilities. Gargano is a postdoctoral fellow at Johnson Space Center. He is also affiliated with the Lunar Planetary Institute.

What lunar soil reveals about water sources

Scientists analysed lunar soil collected during Apollo Moon missions. The samples came from six missions over fifty years ago. All landings occurred near the Moon’s equator facing Earth. Despite limited locations, the samples continue revealing new discoveries.

Researchers identified carbon rich meteorite material mixed within lunar soil. At least one per cent of samples contained meteorite remnants. These meteorites partially vaporised during powerful impact events. Scientists estimated how much water these space rocks carried.

Earth experiences far more meteorite impacts compared with the Moon. Researchers adjusted calculations using Earth’s higher impact rate. Earth receives roughly twenty times more impacts than the Moon. Even after adjustment, meteorites supplied only a small portion.

Why oxygen isotopes matter for impact studies

The team used a new method studying lunar regolith. Regolith is fine dust and debris covering the Moon. Scientists measured triple oxygen isotopes within the samples. These isotopes remain stable even during intense meteorite impacts.

That stability allows clear identification of incoming meteorite material. Traditional methods relied on metal elements altered by impacts. Repeated collisions can change metal based chemical signatures. Oxygen isotopes provide a clearer long term impact record.

Earth cannot preserve such an ancient impact history. Tectonic movement and weather erase most surface evidence. The Moon lacks these processes, preserving billions of years. This makes lunar soil a valuable scientific archive.

Gargano said lunar regolith records neighbourhood impacts across deep time. The isotope fingerprint isolates impactor signals from altered mixtures. Those mixtures endured melting, vaporisation, and repeated reworking processes.

Why the findings matter for future Moon missions

Meteorite delivered water matters more for the Moon itself. The Moon holds water inside permanently shadowed polar regions. These regions receive no sunlight and remain extremely cold. They are among the coldest places in the solar system.

Such icy areas are important for science and exploration. They will support future NASA Artemis missions. Future lunar samples should deepen understanding of water delivery. Scientists also expect insights into early solar system history.