Planetary scientists examined oxygen isotopes present in lunar soil retrieved during the Apollo missions. This analysis indicated that the intense meteoroid bombardment approximately four billion years ago contributed only a minor fraction to Earth’s water supply, prompting scientists to reconsider established theories about its genesis.
The prevailing belief previously held that meteorites played a central role in delivering water to our planet during the early formation stages of the Solar System via planetary bombardment. The recent study, conducted by specialists from NASA’s Lyndon B. Johnson Space Center collaborating with the Lunar and Planetary Institute, employed refined analytical techniques applied to lunar regolith—the dust covering the Moon’s surface. The findings were published in the journal Proceedings of the National Academy of Sciences.
It was determined that, even under the most favorable estimations, meteorites impacting Earth around four billion years ago could have conveyed only a small percentage of its total water. The Moon preserves a chronicle of ancient collisions within the Earth-Moon system stretching back billions of years, whereas such evidence is erased in Earth’s active crust and atmosphere.
Regolith analysis traditionally relied on examining metallic components, which, through numerous impacts, can mix and complicate the accurate determination of the original meteoritic composition. The novel procedure utilizes triple oxygen isotopes. These act as unique “fingerprints” that remain unaltered during impacts, enabling the identification of the composition of meteoroids that struck the Earth-Moon system.
Measurements reveal that a minimum of 1% of the regolith’s mass consists of material originating from carbon-rich meteorites, some of which vaporized upon striking the Moon. Based on the known characteristics of these specific meteorite types, the researchers calculated the quantity of water they contained.
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