Wednesday , January 20 2021

Evidence of water movement found in meteorites that only recently fell on Earth


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A team of researchers affiliated with institutions in Australia, the US and France has found evidence of relatively recent water movement in meteorites that have only recently collided with Earth. In her paper published in the journal Science, the group describes their study of carbonaceous chondrite (CC) meteorites that landed on the earth’s surface in the past century and what they found.

Many scientists believe that the water present on Earth came from meteorites. This theory is difficult to prove because the meteorites hitherto recovered do not contain water and because chemical reactions that may have comet-dried water occurred millions of years ago. In this new effort, the researchers looked at the idea from a different angle – they studied isotopes in meteorites that landed on Earth just over the past century.

Preliminary research has suggested that most, if not all, CC meteorites formed about 4.5 billion years ago as part of larger asteroids. To find out if recent arrivals may have evidence of a water history, the researchers looked at distribution of uranium and thorium in samples – the former is water-soluble, while the latter is not. Logic suggests that if water ever existed in the meteorite, it would have to move when it melts, and that motion would be reflected in the distribution of thorium and uranium isotopes. Also, both isotopes have short half-lives, which means that if their distribution were found in meteorites, they would have occurred relatively recently – in the order of a few million years.

When studying nine of the meteorites, the researchers found the distributions they were looking for – a finding that suggested that water was moving by melting, probably over the past 1 million years. The researchers suggest that such meteorites could not only have supplied water to Earth during the planet’s formative years; they could do the same in the very recent past. She notes that this idea could be tested by sticking asteroids before hitting Earth, as was recently done by Japanese and American spacecraft.

Study finds meteoric evidence for a previously unknown asteroid

More information:
Simon Turner et al. Carbonaceous chondrite meteorites have been flowing for the past million years, Science (2021). DOI: 10.1126 / science.abc8116

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