Impact Crater May Be Dinosaur Killer's Baby Cousin (bbc.com) 21
Researchers have discovered a second impact crater on the other side of the Atlantic that could have finished off what was left of the dinosaurs, after an asteroid known as Chicxulub slammed into what is now the Gulf of Mexico 66 million years ago. The BBC reports: Dubbed Nadir Crater, the new feature sits more than 300m below the seabed, some 400km off the coast of Guinea, west Africa. With a diameter of 8.5km, it's likely the asteroid that created it was a little under half a kilometre across. The hidden depression was identified by Dr Uisdean Nicholson from Heriot-Watt University, Edinburgh, UK. [...] "Our simulations suggest this crater was caused by the collision of a 400m-wide asteroid in 500-800m of water," explained Dr Veronica Bray from the University of Arizona, US. "This would have generated a tsunami over one kilometre high, as well as an earthquake of Magnitude 6.5 or so. "The energy released would have been around 1,000 times greater than that from the January 2022 eruption and tsunami in Tonga."
Dr Nicholson's team has to be cautious about tying the two impacts together. Nadir has been given a very similar date to Chicxulub based on an analysis of fossils of known age that were drilled from a nearby borehole. But to make a definitive statement, rocks in the crater itself would need to be pulled up and examined. This would also confirm Nadir is indeed an asteroid impact structure and not some other, unrelated feature caused by, for example, ancient volcanism. [...] Prof Sean Gulick, who co-led the recent project to drill into the Chicxulub Crater, said Nadir might have fallen to Earth on the same day. Or it might have struck the planet a million or two years either side of the Mexican cataclysm. Scientists will only know for sure when rocks from the west African crater are inspected in the lab. "A much smaller cousin, or sister, doesn't necessarily add to what we know about the dinosaurs' extinction, but it does add to our understanding of the astronomical event that was Chicxulub," the University of Texas at Austin researcher told BBC News.
Dr Nicholson's team has to be cautious about tying the two impacts together. Nadir has been given a very similar date to Chicxulub based on an analysis of fossils of known age that were drilled from a nearby borehole. But to make a definitive statement, rocks in the crater itself would need to be pulled up and examined. This would also confirm Nadir is indeed an asteroid impact structure and not some other, unrelated feature caused by, for example, ancient volcanism. [...] Prof Sean Gulick, who co-led the recent project to drill into the Chicxulub Crater, said Nadir might have fallen to Earth on the same day. Or it might have struck the planet a million or two years either side of the Mexican cataclysm. Scientists will only know for sure when rocks from the west African crater are inspected in the lab. "A much smaller cousin, or sister, doesn't necessarily add to what we know about the dinosaurs' extinction, but it does add to our understanding of the astronomical event that was Chicxulub," the University of Texas at Austin researcher told BBC News.
Very cool actually (Score:5, Interesting)
There's been a number of papers I believe where geophysicists and astronomers have theorized that this wasn't one impact but multiple impacts. The evidence is that the layer of iridium from the asteroid and ash seems to have been fanned out in a specific direction away from the Yucatan, which would be expected if the bolides hit at an angle and/or if there were multiple impacts.
So yeah, do a core sample like they did in the 70's for the Yucatan, which was the smoking gun when they tied the tektites they found to those found in the KT boundary in fossil layers the world over.
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Interesting. So if I'm parsing what you wrote correctly, why do they think multiple impacts more likely than an angled impact? I would expect an angled impact to be more likely to happen, but I bet there's something else they are basing this on, like the fan-shape is much more like multiple impacts or whatever. Just curious what it was.
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That's why I wrote "and/or". It can be both multiple impacts and multiple impacts at an angle. The different locations would be expected because if the bolides are spread out in space, there's time for the earth to turn so that the one after the Yucatan hits somewhere off africa.
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Purely speculative: I don't know if we'd have a way to verify it, but there's a chance the big-boy body had a facture from impacts on its journey and split when it hit the atmosphere, jettisoning fragments in various directions while the main body ended up being the Chicxulub impactor. Or, heck, maybe there was a collision way out there and the Earth got a nice sprinkling for a period of anywhere from a few days, to a few years either side of the Chicxulub impactor.
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Yes, impact craters in the solar system often come in multiples, indicating an object that fragments as it approaches (presumably due to tidal forces). So it's reasonable that there would be more than one crater.
Shoemaker-Levy 9's impact on Jupiter was a live view of this.
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There's some recent (2020) research [nature.com] suggesting that the Chicxulub impact was at a steep angle (around 60 degrees) and the global ejecta spread was in fact more or less symmetrical. The idea that there was more ejecta landing on North America turns out to be incorrect as the same layers have now also been found in the South. The crater itself shows asymmetry, but not as much as would be expected if the angle was much shallower.
If the suggested direction of the Chicxulub asteroid arriving from the Northeast i
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Well, it's always been considered as a possibility, because multiple impacts aren't terribly uncommon. but specific claims concerning this impact ? ... [citation required].
Energy comparison (Score:2)
"The energy released would have been around 1,000 times greater than that from the January 2022 eruption and tsunami in Tonga."
Because this is a BBC article, it's nice to see the energy comparison using something other than the Hiroshima/Nagasaki atomic blasts that past US articles used. Even the Smithsonian article on the Tonga eruption changed to reporting just straight megaton energy levels.
"This is a preliminary estimate, but we think the amount of energy released by the [January 2022 Tonga] eruption was equivalent to somewhere between 4 to 18 megatons of TNT," says Jim Garvin, chief scientist at NASA's Goddard Space Flight Center, to NASA's Earth Observatory blog. Tonga eruption was more powerful than an atomic bomb [smithsonianmag.com]
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1 megaton of TNT releases roughly the same energy as an earthquake with magnitude 7.2. The magnitude scale is logarithmic so that 1 kiloton is 5.2Mw and 1000 megatons is 9.2Mw. An increase of just 0.2Mw means doubling the energy. The article mentions a 6.5Mw earthquake resulting from the impact but it's important to realise that that would be an extremely small fraction of the total energy released. 1000 times more than the Tonga eruption could be as high as 10Mw.
Dinosaur aliens ensuring their dominance (Score:3)
They had no desire to see their descendants have to face genetically engineered Deinonychus Space Marines.
Sort of like their version of a pre-emptive "nuke them from orbit, it's the only way to be sure, but use a meteor instead in case the Galactic Council later sends investigators."
Say, that could explain our era's UFOs. The overworked Space Patrol finally investigating a possible genocide.
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I like your style. I'd buy that book.
Exciting field of asteroid relationships ... (Score:3)
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Asteroid genealogy is a very exciting field, but I'm fearful that some moron is going to start investigating asteroid astrology, and then we're all in trouble. How do you compare signs when asteroids aren't all in the same location? Does each asteroid have its own separate set of astrological signs? Or do they all share a single vantage point for signs, like, say, 1 AU from the star Sol?
Dammit! Now I've done it.
So, maybe the comet was breaking apart? (Score:2)
That would explain a lot.
Of course, neither the DoD nor Bruce Armashitty Willis will take note that this is *exactly* what would happen if you tried hitting an earth impactor with a nuke closer than, say, the Moon. Or maybe closer than L5.
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Then you can get started on Archimedes Plutonium.
Congratulate the BBC (Score:1)
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Well, it's not funded by advertising. The same reporting crew also put together a 10min slice of interviews for the "Inside Science" radio programme [bbc.co.uk], and you'll probably hear other material too over coming weeks and years.