New Blow Against Dinosaur-killing Asteroid Theory

marco_polo

Was gonna post this in the Permian Extinction Thread but I think it perhaps deserves its own. Up to you Galvasean

The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a new article. On the basis of evidence suggesting that the Chicxulub impact predates the K-T boundary by as much as 300,000 years, Geologist argue that an impact didn't lead to mass extinction 65 million years ago.

http://www.sciencedaily.com/releases/2009/04/090427010803.htm

Mena

O.o that is interesting...

sciencedaily.com wrote:

At one site at El Penon, the researchers found 52 species present in sediments below the impact spherule layer, and counted all 52 still present in layers above the spherules.

Does this rule out the impact or is there another line of thinking?

sciencedaily.com wrote:

Keller suggests that the massive volcanic eruptions at the Deccan Traps in India may be responsible for the extinction, releasing huge amounts of dust and gases that could have blocked out sunlight and brought about a significant greenhouse effect.

Would the eruptions at the Deccan Traps really cause more "havoc" than the impact of said meteor? 180Km crater would indicate something not of insignificant size and I've always been led to believe this type of impact would be an E.L.E.

marco_polo

Mena wrote: »

O.o that is interesting...



Does this rule out the impact or is there another line of thinking?



Would the eruptions at the Deccan Traps really cause more "havoc" than the impact of said meteor? 180Km crater would indicate something not of insignificant size and I've always been led to believe this type of impact would be an E.L.E.

I am no expert in either Geology or extinctions but if the dates are accurate then 300,000 years does seem quite a long time period before the KT boundary, if the dates are accurate, certainly for the impact to be the sole cause.

I believe it is not the first time this has been suggested by this research team and hotly disputed by others (on the grounds of earthquake or tsunami disturbance causing the sediment layers above the impact spherules), but this paper seems to be the team coming back with refined data to support their position.

For us laymen is probably a matter of sitting back and seeing who ultimately wins the debate.

Even if not the ultimate or sole cause it is hard to see how an impact of this size could not have had a massive effect on life at the time.

( I am not sure of the position of the researchers are as to whether it had no effect or just that the effect is overstated)

Saruman

I thought a single mass extinction was ruled out years ago. I saw on a documentary a few years back that it is more likely that it happened over thousands or millions of years and a lot of it had to do with climate change, changes in oxygen levels as well as the odd impact.

marco_polo

Saruman wrote: »

I thought a single mass extinction was ruled out years ago. I saw on a documentary a few years back that it is more likely that it happened over thousands or millions of years and a lot of it had to do with climate change, changes in oxygen levels as well as the odd impact.

Not ruled out I would say but still definately not settled.

The position of Keller is that it was not the sole cause of the extinction, her views seem to be much like you describe above (Perhaps she was involved in the documentary).

More reading here from circa 2003 or so

http://www.sciencedaily.com/releases/2003/09/030926065930.htm
http://www.princeton.edu/pr/pwb/03/0922/
http://www.geolsoc.org.uk/gsl/null/lang/en/page2519.html

marco_polo

In a similar vein:

New fossil evidence suggests some dinosaurs survived for up to half a million years after the impact in remote parts of New Mexico and Colorado. For about half a million years or so, given the similar timescales involved, it seems to lend more creedance to the paper above.

Scientists recently analyzed dinosaur bones found in the Ojo Alamo Sandstone in the San Juan Basin. Based on detailed chemical investigations of the bones, and evidence for the age of the rocks in which they are found, the researchers think some dinosaurs outlived the crash that occurred 65 million years ago and stuck around for a while.

http://www.livescience.com/animals/090428-lost-dinosaurs.html

Unusual to see two similar papers that seem to support each other in a matter of days. Perhaps the tide really is turning for good on the single impact hypothesis.

Galvasean

What an interesting taught, a few rugged dinos battling it out after the great meteor impact. Kind of heroic, like the Land Before Time, only without a happy ending.

*not counting birds of course.

marco_polo

Galvasean wrote: »

What an interesting taught, a few rugged dinos battling it out after the great meteor impact. Kind of heroic, like the Land Before Time, only without a happy ending.

*not counting birds of course.

I must say I never would have been a true believer that all dinosaurs could possibly have disappeared almost instantly off the face of the earth.* Given the vast diversity of dinosaur species if other, admittedly generally smaller animals could have survived, then I find it hard to not believe that at least some smaller dinos managed to soilder on afterwards, at least until some other change also tipped them over the edge*.

*also sans-bird.

Galvasean

Well, even if a few (non avian) dinosaurs did survive a few hundred or maybe even a few thousand years after the impact their population sizes would have most likely been quite small and their dispersal/habitats quite limited. Taking into account the odds against any/every single animal fossilizing, let alone being discovered and identified by humans millions of years later it is truly amazing that we found them at all. I had always hoped (in an outspoken sort of way) that such a find would be uncovered in my lifetime (but never hazarded much hope), if only to act as a testament to the durability of the (large) dinosaurs.

Galvasean

National Geographic have picked up the story. Apparently hadrosaurs, tyrannosaurs and ankylosaurs were among the late survivors.
http://news.nationalgeographic.com/news/2009/05/090501-dinosaur-lost-world.html

marco_polo

Galvasean wrote: »

National Geographic have picked up the story. Apparently hadrosaurs, tyrannosaurs and ankylosaurs were among the late survivors.
http://news.nationalgeographic.com/news/2009/05/090501-dinosaur-lost-world.html

Interesting. Sometimes it seems the more we discover the less we know about anything. A few years ago the KT Extinction was pretty well a closed case. I forget who said it but I certainly agree with the sentiment, it is the questions, not the answers that make science interesting.

Galvasean

That's one of the things I love about palaeontology. Every answer reveals a new question. It's like a never ending quest for knowledge.

Its weird how everything I read as a kid is now more or less wrong. Example: I recently aquired dinosaurs from over 20. Back then

- Brachiosaurus was the biggest dinosaur
- T. rex was the biggest meat eater.
- Diplodocus was the longest dinosaur.
- Spinosaurus' head was like a generic theropod.
- No dinosaurs had feathers.

Just as a few examples.

Capt'n Midnight

Galvasean wrote: »

Its weird how everything I read as a kid is now more or less wrong. /QUOTE]dinosaurs were extinct - birds
brontosarus - doesn't exist anymore

marco_polo

Galvasean wrote: »

That's one of the things I love about palaeontology. Every answer reveals a new question. It's like a never ending quest for knowledge.

Its weird how everything I read as a kid is now more or less wrong. Example: I recently aquired dinosaurs from over 20. Back then

- Brachiosaurus was the biggest dinosaur
- T. rex was the biggest meat eater.
- Diplodocus was the longest dinosaur.
- Spinosaurus' head was like a generic theropod.
- No dinosaurs had feathers.

Just as a few examples.

It seems so matter of fact now you have just reminded me what a big deal the confirmation of the first feathered dinosaur was, as before that the bird <- dino theory was a considered plausible at best if I am not mistaken.

It is only in the last year or two I have rediscovered my interest in all of this dinosaur stuff and I was amazed how much had changed from what I remembered (all the stuff you listed basically). As a younger fella I was obsessed with all this stuff. however I was also an IT nerd back in the 80s (when it was even less cool then ) so ultimately that won out (Just to clarify I am still under 30, just by the barest of margins though ).

Galvasean

New research indicates that the meteor impact caused lots of carbon monoxide to be released into the atmosphere. It goes on to suggest that this caused a spike in global temperatures whichled to the mass extinction.
However the research is hotly contested, with others pointing out that the global 'nuclear winter' generated by the impact would have more than cancelled out any increases of temperature.

Read more here:
http://www.msnbc.msn.com/id/30833535/

Michael Reilly wrote:

When a giant asteroid slammed into the Yucatan Peninsula 65 million years ago, the results were devastating: rock and ocean water vaporized, searing debris flung into outer space, and a smoldering hole in the Earth almost 75 miles wide.

Scientists debate whether the cataclysm was enough to wipe out the dinosaurs. But a new set of experiments shows the impact produced a huge amount of carbon monoxide, a compound commonly found in car exhaust. The sudden pulse of gas may have been enough to cause a large spike in global temperatures, and trigger a mass extinction.

Yasuhito Sekine of the University of Tokyo and a team of researchers simulated the impact in miniature by firing small pieces of metal into chunks of calcite, a carbon-rich mineral common in the shallow seas of the Cretaceous period. The collisions vaporized their targets, and produced about twice as much carbon monoxide (CO) as carbon dioxide (CO2).

he team's research was published this month in the journal Earth and Planetary Science Letters.

Though not a direct greenhouse gas, carbon monoxide starts a cascade of chemical reactions in the atmosphere that can have huge consequences for global climate. It also promotes the production of nitric oxide (NO), which spawns ozone (O3), a greenhouse gas and poison when abundant near Earth's surface.

"The concentrations of CO and O3 formed after the Chicxulub impact are too low to kill animals and dinosaurs directly, but would cause weak health hazards to animals," Sekine told Discovery News. "The intense increase in O3 after the impact would have caused serious damage not only on plants themselves but also the whole ecosystem at that time."

"They might have a point that carbon monoxide is released on impact," Alexander Pavlov of the National Aeronautic and Space Administration's Goddard Space Flight Center said. "The issue is not what's coming out from impact, but how does it compare to the carbon dioxide coming from forest fires?"

A layer of ash found in in several parts of the world hints that the impact touched off a global firestorm that wiped out much of the planet's forests. If so, the amount of carbon dioxide released during those fires would dwarf any emissions from the impact itself.

"Even if they're right, the warming wouldn't have had that much of an effect," Pavlov said. He argues that the firestorm, along with a subsequent nuclear winter likely dominated global climate for the first few years after the impact, and played the biggest role in the extinction.

Mickeroo

I always find the fact that life recovered at all from an impact like that completely mind boggling. Dont know if ye saw this:

https://www.youtube.com/watch?v=-zvCUmeoHpw

Galvasean

Mickeroo wrote: »

I always find the fact that life recovered at all from an impact like that completely mind boggling. Dont know if ye saw this:

https://www.youtube.com/watch?v=-zvCUmeoHpw

Luckily the meteor that hit 65 million yeas ago was only half the size of Mount Everest. The one in that video is the size of a continent!

Mickeroo

Galvasean wrote: »

Luckily the meteor that hit 65 million yeas ago was only half the size of Mount Everest. The one in that video is the size of a continent!

Yea i know! Nice video though.

Galvasean

Interesting, not only can life bounce back from the devastating effects of meteorite impacts, but it seems it can benefit too.
Also, the study would indicate that life on Earth originated 4.5 billion years ago as opposed to 3.9 as previously estimated.

http://www.sciencecentric.com/news/article.php?q=09052106-asteroid-attack-3-9-billion-years-ago-may-have-enhanced-early-life-on-earth

The bombardment of Earth nearly 4 billion years ago by asteroids as large as Kansas would not have had the firepower to extinguish potential early life on the planet and may even have given it a boost, says a new University of Colorado at Boulder study.

Impact evidence from lunar samples, meteorites and the pockmarked surfaces of the inner planets paints a picture of a violent environment in the solar system during the Hadean Eon 4.5 to 3.8 billion years ago, particularly through a cataclysmic event known as the Late Heavy Bombardment about 3.9 million years ago. Although many believe the bombardment would have sterilised Earth, the new study shows it would have melted only a fraction of Earth's crust, and that microbes could well have survived in subsurface habitats, insulated from the destruction.

'These new results push back the possible beginnings of life on Earth to well before the bombardment period 3.9 billion years ago,' said CU-Boulder Research Associate Oleg Abramov. 'It opens up the possibility that life emerged as far back as 4.4 billion years ago, about the time the first oceans are thought to have formed.'

A paper on the subject by Abramov and CU-Boulder geological sciences Professor Stephen Mojzsis appears in the 21 May issue of Nature.

Because physical evidence of Earth's early bombardment has been erased by weathering and plate tectonics over the eons, the researchers used data from Apollo moon rocks, impact records from the moon, Mars and Mercury, and previous theoretical studies to build three-dimensional computer models that replicate the bombardment. Abramov and Mojzsis plugged in asteroid size, frequency and distribution estimates into their simulations to chart the damage to the Earth during the Late Heavy Bombardment, which is thought to have lasted for 20 million to 200 million years.

The 3-D models allowed Abramov and Mojzsis to monitor temperatures beneath individual craters to assess heating and cooling of the crust following large impacts in order to evaluate habitability, said Abramov. The study indicated that less than 25 percent of Earth's crust would have melted during such a bombardment.

The CU-Boulder researchers even cranked up the intensity of the asteroid barrage in their simulations by 10-fold - an event that could have vaporised Earth's oceans. 'Even under the most extreme conditions we imposed, Earth would not have been completely sterilised by the bombardment,' said Abramov.

Instead, hydrothermal vents may have provided sanctuaries for extreme, heat-loving microbes known as 'hyperthermophilic bacteria' following bombardments, said Mojzsis. Even if life had not emerged by 3.9 billion years ago, such underground havens could still have provided a 'crucible' for life's origin on Earth, Mojzsis said.

The researchers concluded subterranean microbes living at temperatures ranging from 175 degrees to 230 degrees Fahrenheit would have flourished during the Late Heavy Bombardment. The models indicate that underground habitats for such microbes increased in volume and duration as a result of the massive impacts. Some extreme microbial species on Earth today - including so-called 'unboilable bugs' discovered in hydrothermal vents in Yellowstone National Park - thrive at 250 F.

Geologic evidence suggests that life on Earth was present at least 3.83 billion years ago, said Mojzsis. 'So it is not unreasonable to suggest there was life on Earth before 3.9 billion years ago. We know from the geochemical record that our planet was eminently habitable by that time, and this new study sews up a major problem in origins of life studies by sweeping away the necessity for multiple origins of life on Earth.'

Most planetary scientists believe a rogue planet as large as Mars smacked Earth with a glancing blow 4.5 billion years ago, vaporising itself and part of Earth. The collision would have created an immense vapour cloud from which moonlets, and later our moon, coalesced, Mojzsis said. 'That event, which preceded the Late Heavy Bombardment by at least 500 million years, would have effectively hit Earth's re-set button,' he said.

'But our results strongly suggest that no events since the moon formation were capable of destroying Earth's crust and wiping out any biosphere that was present,' Mojzsis said. 'Instead of chopping down the tree of life, our view is that the bombardment pruned it.'

The results also support the potential for microbial life on other planets like Mars and perhaps even rocky, Earth-like planets in other solar systems that may have been resurfaced by impacts, said Abramov.

'Exactly when life originated on Earth is a hotly debated topic,' says NASA's Astrobiology Discipline Scientist Michael H. New, manager of the Exobiology and Evolutionary Biology program. 'These findings are significant because they indicate life could have begun well before the LHB, during the so-called Hadean Eon of Earth's history 3.8 billion to 4.5 billion years ago.'