If you think the asteroid that made theChicxulub Craterwas terrifying , and no doubt nearby dinosaurs did , consider the force of an aim weighing up to 30 times as much smashing into Earth . grounds for just such an event has been feel , and geologists have been able to date it with strange precision .
Around 3.8 billion years ago the Moon was bombarded with huge asteroids , leaving crater that afterwards filled with lava and became what we now call “ seas ” . terra firma must have have a like set of impacts , but a combination of architectonic force-out and erosion from breaking wind and waves have decimate all tincture of craters older thanthree billion years .
This , however , does n’t mean we can not incur grounds of such events . material thrown up in the collision , like droplet spraying when a stone hit a pool , can leave a distinctive trace long after the impingement volcanic crater is gone . This is whatDr . Andrew Gliksonof the Australian National University found when he re - see a practice session gist need from Marble Bar , Western Australia , in some of the onetime continental crust on Earth .
Glikson told IFLScience the substance was in the first place collected a decennary ago for other use , but he checked it for the glass pearl have it off as spherule that are create by big impacts . object that looked like spherules were found , and their metallic penning corroborate asteroidal origin . And these turned out to be more interesting than Glikson could have jolly hoped .
The size of these spherule bespeak they were formed in a truly tremendous wallop . Andrew Glikson / ANU
For one thing , they were unusually large . Glikson explain to IFLScience , “ Other researchers have shown that the larger the impact , the magnanimous the spherule . ” Based on the 1 - 2 millimeter diameter of the spherules , Glikson conclude the asteroid would have been 20 to 30 klick ( 12 to 19 miles ) in diameter .
" The impact would have triggered earthquake orders of magnitude greater than sublunary earthquake , it would have caused vast tsunami and would have made cliffs crumble , " Glikson allege in astatement .
Moreover , the spherules were found wedged between two volcanic layers , the upper of which Glikson told IFLScience might have been trigger by the impact itself . Uranium - wind isotopeanalysis of volcanic crystals enable Glikson to go out the collision with unusual preciseness to 3.45 to 3.46 billion eld ago . This makes it the secondly oldest known impact , as well as one of the large in Earth ’s history .
" precisely where this asteroid strike the earth stay a mystery , " Gliksonsaid . " This is just the tip of the iceberg . We ’ve only found grounds for 17 impacts sr. than 2.5 billion years , but there could have been hundreds . Asteroid strikes this big result in major tectonic chemise and extensive magma flows . They could have importantly affected the way the Earth evolved . "
The determination was put out inPrecambrian Research . Glikson and his co - authors confirm the spherules have a different lineage from those found in sediments just 40 kilometer ( 25 international nautical mile ) to the west that come from an impact 3.47 billion year ago .
These sediments at Marble Bar , Western Australia , turn back tell - story theme song of an epic asteroid impact . Andrew Glikson / ANU
