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Astronomie - Lunar glass samples reveal Moon meteorite impacts that mirrored those happening on Earth millions of years ago

30.09.2022

The finding sheds new light on asteroid dynamics in the inner solar system.

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Chang'e-5 glass beads. Credit: Beijing SHRIMP Center, Institute of Geology, CAGS

Researchers have found the timing and frequency of meteorite impacts on the Moon millions of years ago coincides with some of the largest meteorite impacts on Earth – like the one that was responsible for hastening the extinction of the dinosaurs.

By analysing samples of lunar soil brought back to Earth by the Chang’e-5 mission the researchers were able to reconstruct the history of lunar meteorite impacts.

Their findings suggest that the frequency of meteorite impacts on the Moon may have been mirrored on Earth, and that major impact events on Earth were not stand-alone events and instead were accompanies by a series of smaller impacts.

The study has been published in Science Advances.

“We combined a wide range of microscopic analytical techniques, numerical modelling, and geological surveys to determine how these microscopic glass beads from the Moon were formed and when,” says lead author Professor Alexander Nemchin, from the Space Science and Technology Centre (SSTC) in the School of Earth and Planetary Sciences at Curtin University in Perth.

“We found that some of the age groups of the lunar glass beads coincide precisely with the ages of some of the largest terrestrial impact crater events, including the Chicxulub impact crater responsible for the dinosaur extinction event.”

“The study also found that large impact events on Earth, such as the Chicxulub crater 66 million years ago, could have been accompanied by a number of smaller impacts.”

“If this is correct, it suggests the age-frequency distributions of impacts on the Moon might provide valuable information about the impacts on the Earth or inner solar system,” says Nemchin.

The international team of researchers analysed 215 samples of microscopic silica glass beads that were found in lunar soil brought back to Earth by the Chinese National Space Agency’s Chang’e-5 Lunar mission.

The glass was created by the intense heat and pressure of meteorite impacts. So, by determining their age distributions researchers could construct a timeline of lunar bombardments. They used uranium-lead dating – a technique that involves measuring the ratio of uranium isotopes to stable lead isotopes. 

And by analysing the silicate glass’ distinctive chemical composition they could also model the impact formation and ejection that would have led to their formation.

The researchers found that the impacts that created the samples would have resulted in craters between 100 and 1,300 meters in diameter and ejecta temperatures between 827°C and 1,427 °C, potentially spewing these glasses at distances more than 150 kilometres upon impact.

Co-author of the study, Associate Professor Katarina Miljkovic from Curtin’s SSTC, says future comparative studies could give even further insight into the geological history of the Moon.

“The next step would be to compare the data gleaned from these Chang’e-5 samples with other lunar soils and crater ages to be able to uncover other significant Moon-wide impact events which might in turn reveal new evidence about what impacts may have affected life on Earth,” says Miljkovic.

Quelle: COSMOS

 

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