Lunar rocks suggest Earth's water may not have come from meteorites

A team led by Dr. Tony Gargano analyzed Apollo lunar samples with high-precision triple oxygen isotopes and concluded that meteorites since the Late Heavy Bombardment could only have supplied a small fraction of Earth's water; the paper was published in PNAS.

Researchers report that analysis of Apollo lunar rocks using high-precision triple oxygen isotopes suggests meteorite impacts since the Late Heavy Bombardment could only have supplied a small fraction of Earth's water. The work was led by Dr. Tony Gargano at the Universities Space Research Association's Lunar and Planetary Institute and the University of New Mexico. The Moon preserves a long-term impact record that Earth does not, because Earth’s tectonic activity renews its surface. The study appeared in the Proceedings of the National Academy of Sciences. Key findings: - The team measured triple oxygen-isotope compositions in a large suite of Apollo lunar soils and regolith samples. - They found at least about 1% of the lunar regolith mass is impact-related material, interpreted as partly vaporized carbonaceous (C-type) meteorite input. - From those isotope offsets the researchers set upper limits showing late meteorite delivery could only account for a small fraction of Earth's present water. - The research team included scientists from UNM, the Scripps Institution of Oceanography, NASA JPL, and NASA ARES, and the paper was published in PNAS. - A co-author, Justin Simon, is quoted saying the results do not rule out meteorite contributions but make late meteorite delivery unlikely to be the dominant source of Earth's oceans. Summary: The study uses the Moon's preserved surface as a reference to narrow possible sources of Earth's water and finds that late meteorite impacts are unlikely to supply most of the oceans. Undetermined at this time.