A team of researchers from institutions in Australia, the United States and France has found evidence of relatively recent water movement in meteorites that have recently collided with Earth. In their article published in the magazine Science, the group describes its study of meteorites from carbon chondrite (CC) that landed on the Earth ̵
Many scientists believe that the Earth’s water comes from meteorites. This theory is difficult to prove because the meteorites recovered so far do not contain water and because the chemical reactions that could include comet-borne water occurred millions of years ago. In this new effort, researchers looked at the idea from another angle – they studied isotopes in meteorites that landed on Earth only in the last century.
Previous research suggests that most, if not all, of the meteorites from CC were formed about 4.5 billion years ago as part of larger asteroids. To see if recent arrivals could have evidence of water history, the researchers looked at the distribution of uranium and thorium in the samples – the former being water-soluble and the latter not. Logic suggests that if water ever existed in a meteorite, it would have to move as it melted, and that motion would be reflected in the isotope distribution of thorium and uranium. Also, both isotopes have a short half-life, which means that if their distribution in meteorites could be found, they would occur relatively recently – on the order of several million years.
In studying nine of the meteorites, the researchers found the distribution they were looking for – a finding that suggests the water was moving due to melting, probably in the last 1 million years. Researchers suggest that such meteorites could not only have supplied water to Earth during the years of planet formation; they could also do so in the much more recent past. They note that this idea can be tested by sampling asteroids before they hit Earth, as was recently done by Japanese and American spacecraft.
The study found meteoric evidence of a previously unknown asteroid
Simon Turner et al. Carbon chondrite meteorites have tested fluid over the last million years, Science (2021). DOI: 10.1126 / science.abc8116
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Quote: Evidence of water movement found in meteorites that only recently fell to Earth (2021, January 8), retrieved on January 8, 2021 from https://phys.org/news/2021-01-evidence -movement-meteorites-fell-earth.html
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