Overview
- A NASA-led study published in PNAS uses high-precision triple oxygen isotopes on Apollo lunar soils to separate impactor signals from impact-induced alteration.
- Measurements indicate at least about 1% of the regolith by mass is impact-derived material, likely from carbonaceous meteorites that were partially vaporized on impact.
- When scaled to Earth’s higher impact rate—roughly 20 times the Moon’s—the modeled delivery since about 4 billion years ago accounts for only a small percent of ocean water.
- The findings challenge the long-held view that late-arriving, water-rich meteorites were the dominant source of Earth’s oceans, though they do not rule out a minor contribution.
- Authors note the samples come from near-side equatorial Apollo sites, and they point to future Artemis returns from polar and far-side regions to broaden and test these constraints, including implications for lunar polar ice.