Curtin University scientists have discovered Earth’s oldest[-known] asteroid strike occurred at Yarrabubba, in outback Western Australia, and coincided with the end of a global deep freeze known as a Snowball Earth.
[...]Lead author Dr Timmons Erickson, from Curtin’s School of Earth and Planetary Sciences and NASA’s Johnson Space Center, together with a team including Professor Chris Kirkland, Associate Professor Nicholas Timms and Senior Research Fellow Dr Aaron Cavosie, all from Curtin’s School of Earth and Planetary Sciences, analysed the minerals zircon and monazite that were ‘shock recrystallized’ by the asteroid strike, at the base of the eroded crater to determine the exact age of Yarrabubba.
The team inferred that the impact may have occurred into an ice-covered landscape, vaporised a large volume of ice into the atmosphere, and produced a 70km diameter crater in the rocks beneath.
Professor Kirkland said the timing raised the possibility that the Earth’s oldest asteroid impact may have helped lift the planet out of a deep freeze.
[...]“The age of the Yarrabubba impact matches the demise of a series of ancient glaciations. After the impact, glacial deposits are absent in the rock record for 400 million years. This twist of fate suggests that the large meteorite impact may have influenced global climate,” Associate Professor Timms said.
“Numerical modelling further supports the connection between the effects of large impacts into ice and global climate change. Calculations indicated that an impact into an ice-covered continent could have sent half a trillion tons of water vapour – an important greenhouse gas – into the atmosphere. This finding raises the question whether this impact may have tipped the scales enough to end glacial conditions.”
The full research paper, ‘Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognized meteorite impact structure,’ can be found online here [nature.com].
Timmons M. Erickson, Christopher L. Kirkland, Nicholas E. Timms, Aaron J. Cavosie, Thomas M. Davison. Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognised meteorite impact structure. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-019-13985-7 [doi.org]