A team of international researchers has discovered evidence of recent water movement in meteorites that recently impacted the earth. The researchers looked at carbonaceous chondrite (CC) meteorites that impacted the surface of the planet within the past 100 years. The discovery of evidence of recent water movement is significant because many scientists believe water present on the Earth came from meteorites.
Scientists who subscribe to this theory have had difficulty proving it because meteorites recovered so far don’t contain water. Contributing to the difficulty in proving the theory is that chemical reactions that could have involved water delivered by comets occurred millions of years ago. For the new research, the team took a different approach to try to prove the theory involving the study of isotopes in meteorites that impacted the Earth over the last century.
Past research suggests that all CC meteorites formed about 4.5 billion years ago as part of larger asteroids. The team looked at uranium and thorium distribution in meteorite samples. Uranium is water-soluble, while thorium is not. Researchers supposed that if water existed in the meteorite, it would have moved as it melted. The movement would be reflected in the distribution of thorium and uranium isotopes.
Both isotopes also have short half-lives, so if their distributions in the meteorites could be found, that would have occurred relatively recently on a cosmic scale in the order of a few million years. Nine meteorites were studied by the researchers, and the team found distributions they were looking for, suggesting water had been moving due to melting likely within the past million years.
The team believes this type of meteorite could have delivered water to Earth during our planet’s formative years. The idea could be tested by sampling asteroids before they strike the Earth, such as those recently gathered by JAXA and returned to Earth.