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New research finds Earth's oldest-known asteroid strike linked to 'big thaw' - News and Events:
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.
Journal Reference:
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
(Score: 4, Informative) by Coward, Anonymous on Friday February 14 2020, @10:31PM (3 children)
Water molecules in the atmosphere usually condense quickly, but they are talking about H2O reaching the upper atmosphere where the lifetime is unknown. The H2O-driven greenhouse theory seems rather speculative.
Everyone who sees big piles of snow at the end of winter notices how dirty they are. As the white snow melts, small concentrations of dirt near the surface become concentrated, and the top layer gets ever dirtier, causing it to melt faster. Dirt causes melting which exposes more dirt. A large asteroid impact would be the perfect dirt-spreading event to kick things off.
(Score: 3, Interesting) by dwilson on Friday February 14 2020, @11:37PM
Worth noting that the melting-faster effect is out-scaled by the volume of the pile of snow. In the city I lived in back in ... 2013? 2015? somewhere in that range, all the snow from the whole city got carted to and dumped in one location. Parking lots, streets, anything where snow was loaded in to a truck, for whatever reason, got dumped there and mounded up by some Caterpiller bulldozers. By the end, the pile was more of a mountain. The Cat's looked like dinky toys at the top. It was easily over 10 stories high, and you could see it from most of the city if you had a rooftop vantage point. This was a city of 100,000 people, mind.
That pile exhibited exactly the same effect you describe: The top layers got dirtier and dirtier as it melted. By the time it was a quarter it's original size, it was pretty much black. ...that was towards the end of August. Still there, still melting. It was still there when the first snows of the next winter fell.
- D
(Score: 2) by Aegis on Friday February 14 2020, @11:50PM (1 child)
Dirty until it snows again....
The asteroid is a one time event, the dust will settle. Snow happens frequently.
(Score: 2) by Coward, Anonymous on Saturday February 15 2020, @12:43AM
Even if it snows, at many latitudes the new snow vanishes every summer by melting to reexpose the dirt. Dropping a global layer of dirt on snow permanently changes the annually averaged albedo. Once the melting starts, albedo drops even further.
Besides, snowball Earth is a dry-atmosphere Earth with little precipitation.