Dino-killing asteroid could have thrust Earth into 2 years of darkness

August 21, 2017, National Center for Atmospheric Research
Credit: CC0 Public Domain

Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.

These new details about how the climate could have dramatically changed following the impact of a 10-kilometer-wide asteroid will be published Aug. 21 in the Proceedings of the National Academy of Sciences. The study, led by the National Center for Atmospheric Research (NCAR) with support from NASA and the University of Colorado Boulder, used a world-class computer model to paint a rich picture of how Earth's conditions might have looked at the end of the Cretaceous Period, information that paleobiologists may be able to use to better understand why some species died, especially in the oceans, while others survived.

Scientists estimate that more than three-quarters of all species on Earth, including all non-avian dinosaurs, disappeared at the boundary of the Cretaceous-Paleogene periods, an event known as the K-Pg extinction. Evidence shows that the extinction occurred at the same time that a large asteroid hit Earth in what is now the Yucatán Peninsula. The collision would have triggered earthquakes, tsunamis, and even volcanic eruptions.

Scientists also calculate that the force of the impact would have launched vaporized rock high above Earth's surface, where it would have condensed into small particles known as spherules. As the spherules fell back to Earth, they would have been heated by friction to temperatures high enough to spark global fires and broil Earth's surface. A thin layer of spherules can be found worldwide in the geologic record.

"The extinction of many of the large animals on land could have been caused by the immediate aftermath of the impact, but animals that lived in the oceans or those that could burrow underground or slip underwater temporarily could have survived," said NCAR scientist Charles Bardeen, who led the study. "Our study picks up the story after the initial effects—after the earthquakes and the tsunamis and the broiling. We wanted to look at the long-term consequences of the amount of we think was created and what those consequences might have meant for the animals that were left."

Other study co-authors are Rolando Garcia and Andrew Conley, both NCAR scientists, and Owen "Brian" Toon, a researcher at the University of Colorado Boulder.

A world without photosynthesis

In past studies, researchers have estimated the amount of soot that might have been produced by global wildfires by measuring soot deposits still preserved in the geologic record. For the new study, Bardeen and his colleagues used the NCAR-based Community Earth System Model (CESM) to simulate the effect of the soot on global climate going forward. They used the most recent estimates of the amount of fine soot found in the layer of rock left after the impact (15,000 million tons), as well as larger and smaller amounts, to quantify the climate's sensitivity to more or less extensive fires.

In the simulations, soot heated by the Sun was lofted higher and higher into the atmosphere, eventually forming a global barrier that blocked the vast majority of sunlight from reaching Earth's surface. "At first it would have been about as dark as a moonlit night," Toon said.

While the skies would have gradually brightened, photosynthesis would have been impossible for more than a year and a half, according to the simulations. Because many of the plants on land would have already been incinerated in the fires, the darkness would likely have had its greatest impact on phytoplankton, which underpin the ocean food chain. The loss of these tiny organisms would have had a ripple effect through the ocean, eventually devastating many species of marine life.

The research team also found that photosynthesis would have been temporarily blocked even at much lower levels of soot. For example, in a simulation using only 5,000 million tons of soot—about a third of the best estimate from measurements—photosynthesis would still have been impossible for an entire year.

In the simulations, the loss of sunlight caused a steep decline in average temperatures at Earth's surface, with a drop of 50 degrees Fahrenheit (28 degrees Celsius) over land and 20 degrees Fahrenheit (11 degrees Celsius) over the oceans.

While Earth's surface cooled in the study scenarios, the atmosphere higher up in the stratosphere actually became much warmer as the soot absorbed light from the Sun. The warmer temperatures caused ozone destruction and allowed for large quantities of water vapor to be stored in the . The water vapor then chemically reacted in the stratosphere to produce hydrogen compounds that led to further ozone destruction. The resulting ozone loss would have allowed damaging doses of ultraviolet light to reach Earth's surface after the soot cleared.

The large reservoir of water in the upper atmosphere formed in the simulations also caused the layer of sunlight-blocking soot to be removed abruptly after lingering for years, a finding that surprised the research team. As the soot began to settle out of the stratosphere, the air began to cool. This cooling, in turn, caused to condense into ice particles, which washed even more soot out of the atmosphere. As a result of this feedback loop—cooling causing precipitation that caused more cooling—the thinning soot layer disappeared in just a few months.

Challenging the model

While the scientists think the new study gives a robust picture of how large injections of soot into the atmosphere can affect the climate, they also caution that the study has limitations.

For example, the simulations were run in a model of modern-day Earth, not a model representing what Earth looked like during the Cretaceous Period, when the continents were in slightly different locations. The atmosphere 66 million years ago also contained somewhat different concentrations of gases, including higher levels of carbon dioxide.

Additionally, the simulations did not try to account for volcanic eruptions or sulfur released from the Earth's crust at the site of the asteroid impact, which would have resulted in an increase in light-reflecting sulfate aerosols in the atmosphere.

The study also challenged the limits of the computer model's atmospheric component, known as the Whole Atmosphere Community Climate Model (WACCM).

"An asteroid collision is a very large perturbation—not something you would normally see when modeling future climate scenarios," Bardeen said. "So the model was not designed to handle this and, as we went along, we had to adjust the model so it could handle some of the event's impacts, such as warming of the stratosphere by over 200 degrees Celsius."

These improvements to WACCM could be useful for other types of studies, including modeling a "nuclear winter" scenario. Like global wildfires millions of years ago, the explosion of nuclear weapons could also inject large amounts of soot into the atmosphere, which could lead to a temporary global cooling.

"The amount of soot created by nuclear warfare would be much less than we saw during the K-Pg extinction," Bardeen said. "But the soot would still alter the climate in similar ways, cooling the surface and heating the upper atmosphere, with potentially devastating effects."

Explore further: Unique model tagging technique identifies soot's pollution source over China

More information: Charles G. Bardeen el al., "On transient climate change at the Cretaceous−Paleogene boundary due to atmospheric soot injections," PNAS (2017). www.pnas.org/cgi/doi/10.1073/pnas.1708980114

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Shootist
1.3 / 5 (6) Aug 21, 2017
Dino-killing asteroid could have thrust Earth into 2 years of darkness


or not.

There are two 300 km astroblemes in Australia, another 300 km astrobleme in Wilkesland, Antarctica and another 300-400 km meteor impact basin near the Falkland Islands. All four are tentatively dated to the 300 to 250 Mya. Each of these four craters is ~300km in diameter. End Permian dates to 252 Mya and is attributed to the Siberian Traps (a large outpouring of Basaltic Lava), not meteor impacts.

Chicxulub crater is ~180km in diameter.

https://www.nyu.e...est.html

AGreatWhopper
5 / 5 (7) Aug 21, 2017
The chicxulub meteor wasn't just another impactor, it hit in shallow seas and that made a huge difference in the spherules that started the fires. All those Permian impacts were deep water, and there was only one continent, populated with tougher, more naturally fringe living organisms, so, as usual, you're just spouting semi-validated data points, stringing them together, working backward from your a priori conclusion...only demonstrating that you're an objectionable, dotty old fart.
IronhorseA
5 / 5 (2) Aug 21, 2017
"End Permian dates to 252 Mya and is attributed to the Siberian Traps (a large outpouring of Basaltic Lava), not meteor impacts. "

There is a potential crater under the ice in Antarctica, detected using radar, that is also much larger than the Chicxulub crater, but is also on the opposite side of the world from where the Siberian traps were located at that time. The shock wave of impact would have gone through the earth and been concentrated at the Traps, potentially causing weakness in the crust that allowed the Traps to form in the first place. This was mentioned on an episode of 'What On Earth' on the Science channel.
torbjorn_b_g_larsson
5 / 5 (6) Aug 21, 2017
Interesting article on impacts of impacts.

@Shootist; Ironhorse: Yes, none of the 5 major mass extinctions have been unarguably attributed. But impact events is considered minor plausibility in the others - including the through Earth refraction model, which is even fringe as far as I know - and specifically the end-Permian Siberian Trap correlation is increasingly robust. There was a recent paper that modeled the trap event phases to the dating of geological stages very precisely, for example.
Caliban
5 / 5 (7) Aug 21, 2017
Dino-killing asteroid could have thrust Earth into 2 years of darkness


or not.

There are two 300 km astroblemes in Australia, another 300 km astrobleme in Wilkesland, Antarctica and another 300-400 km[...]these four craters is ~300km in diameter. End Permian dates to 252 Mya and is attributed to the Siberian Traps (a large outpouring of Basaltic Lava), not meteor impacts.

Chicxulub crater is ~180km in diameter.


So what is your point, Shooty?

I don't even need to dispute or confirm any of your statements, as they are --every last one of them-- IRRELEVANT.

Chicxulub occurred ~66MYA, and wouldn't have been in any way affected by any effects of any of your precursors, the most recent of which --from your own comment-- occurred ~250MYA.

Incidentally, Siberian Traps also entrained the burning of vast amounts of hydrocarbons, which would have resulted in the creation of quite a bit of soot, much as they propose for the Chicxulub impact.
omegatalon
not rated yet Aug 21, 2017
One would think a nuclear winter would kill off all life on the planet instead of being to pick and choose what lives as this is what fuels the folks on the History Channel's Ancient Aliens.
richk
1.8 / 5 (5) Aug 21, 2017
what/mammals/would/survive/impact/damage/plus/two/years/darkness?and/how?
BendBob
4.3 / 5 (6) Aug 21, 2017
Hey richk, I wonder...do any mammals live underground? You asked how, maybe that would help, ya think?
Ojorf
4.3 / 5 (6) Aug 21, 2017
Hey richk, do you think any insects could have survived?
Fish maybe, crustaceans, how about molluscs or amphibians?
Are there any mammals that might eat some of the above?
Must have been a lot of dino carrion about and I imagine some flies and a bad smell.
Whydening Gyre
5 / 5 (4) Aug 21, 2017
Hey richk, do you think any insects could have survived?
Fish maybe, crustaceans, how about molluscs or amphibians?
Are there any mammals that might eat some of the above?
Must have been a lot of dino carrion about and I imagine some flies and a bad smell.

Think about all the fungus that must have flourished....
Ojorf
4 / 5 (4) Aug 21, 2017
Fungusss, yum!
Ojorf
5 / 5 (3) Aug 21, 2017
Must have been a rotten time to have lived through for our ancestors.
rrrander
1 / 5 (7) Aug 22, 2017
Sure it wasn't due to man-made global warming?
FM79
2.6 / 5 (5) Aug 22, 2017
Sure it wasn't due to man-made global warming?

Scientists say Trump caused the extinction of the dinosaurs :D
bschott
1 / 5 (3) Aug 22, 2017
Hey richk, I wonder...do any mammals live underground? You asked how, maybe that would help, ya think?

It sure would! However wouldn't be very hospitable for ANY other ones. Did we all make it here because of moles, groundhogs and trap door spiders? Then there is that whole ectothermic part of reptilian nature...yet here we are with several species of them alive and well....
IOW, a valid question RichK. Not a lot of thought put into the answers though....
Two years of darkness would have extincted all ectotherms....that we have them still kinda blows a whole in the 2 years of darkness theory.
Da Schneib
5 / 5 (4) Aug 22, 2017
@FM97, Trumpoids say scientists caused the extinction of the dinosaurs by discovering global warming.

There, fixed it for you.
Caliban
5 / 5 (5) Aug 22, 2017
Hey richk, I wonder...do any mammals live underground? You asked how, maybe that would help, ya think?


It sure would! However wouldn't be very hospitable for ANY other ones. Did we all make it here because of moles[...]
Two years of darkness would have extincted all ectotherms....that we have them still kinda blows a whole in the 2 years of darkness theory.


Well, biscuit, every school child knows --or should know-- that our mammalian ancestors were rodent-like, and only recently evolved late in the age of the dinosaurs, so that pretty much deals with that part of your comment.

No one has ever said that this period of darkness was complete, or that its effect was entirely uniform on a global scale, so that should settle the second and third parts of your comment.

Needless to say, it would only have taken a few survivors to then recolonize a planet full of now uncontested food resources following the proposed period of relative darkness.
Ojorf
5 / 5 (3) Aug 22, 2017
Imagine fiery rain falling from the skies, back in the days.

Could an animal like a house cat survive this?

They don't swim that much, or go very deep when forced to, not really known for digging holes, burrows, they eat mostly meat, not big on fungi.

What do you think?
bschott
3 / 5 (2) Aug 23, 2017
LMAO...Oh man, the guy who never reads is back....first line of the article:
Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis,

His way of handling the comment without reading the article:
No one has ever said that this period of darkness was complete, or that its effect was entirely uniform on a global scale, so that should settle the second and third parts of your comment.

Perhaps you can find the words partial, regional or intermittent in the article then. Because "shutting down photosynthesis"...indicates a planetary scale.Way to go funnelcake...another "win" for ya.

If you also want to go ahead and link us all to the evolutionary EVIDENCE transitioning subterranean rodentia to homosapiens that would be great...yeah...
bschott
1 / 5 (3) Aug 23, 2017
No one has ever said that this period of darkness was complete, or that its effect was entirely uniform on a global scale, so that should settle the second and third parts of your comment.

A couple more quotes from the article for the illiterate or just plain lazy:
In the simulations, soot heated by the Sun was lofted higher and higher into the atmosphere, eventually forming a global barrier....

And
the simulations, the loss of sunlight caused a steep decline in average temperatures at Earth's surface, with a drop of 50 degrees Fahrenheit (28 degrees Celsius) over land and 20 degrees Fahrenheit (11 degrees Celsius) over the oceans.

Note the terminology funnelcake...not "parts of the oceans" and "parts of the land"...or "parts of the earths surface".
P.S.....
uncontested food resources

LMAO....awww funnelcake....

Caliban
4 / 5 (4) Aug 24, 2017
Well, there you go again, biscuit, interpreting to suit yourself. Nowhere in the article do they say that the effects were uniform, globally.

Are you aware of the meaning of the word average? or "could have"?

Do you think that if they meant global shut down of photosynthesis, that they would say so, instead of leaving it up to readers to interpret? Do you really think that there would be any marine plants in the ocean today if there had been a 100%, global shut down of photosynthesis? Do you mean to suggest that all marine plants extant have evolved since this impact occurred?

Do you question on what basis they claim global wildfires?

I don't suppose it matters. I made the unfortunate mistake of failing to qualify my assertion by adding that "no one(previously engaged in researching this event) said..." and
compounded the error by thinking you might possess any background understanding of this event.

Anyway, glad to have provided you with a fun time.
bschott
not rated yet Aug 24, 2017
Well, there you go again, biscuit, interpreting to suit yourself.

Um...what do you think you're doing funnelcake?
Are you aware of the meaning of the word average? or "could have"?

Yes...are you aware that my agreement with RichK's post, the one you originally responded to, was that there is no way the earth experienced 2 years of darkness if we are here right now? And that there is no way photosynthesis shut down if we are here right now?
Do you question on what basis they claim global wildfires?

I question the basis of the conclusion that the earth was dark for 2 years. You are both trying to say I am wrong while simultaneously providing my stance with ammunition.
But what can one expect from a guy who just said there were uncontested food resources in the environment they paint here....perhaps you may have forgot that, in their scenario all the food died....again, why I am disagreeing with the article.
Thanks for the laughs Funnelcake.
Caliban
not rated yet Aug 24, 2017
Well, then biscuit, thanks for clarifying that you were disagreeing with the article.

Also, you are, as I stated earlier, welcome for the fun.

Please allow me to return the favor, by providing you the answer to your earlier inquiry,

If you also want to go ahead and link us all to the evolutionary EVIDENCE transitioning subterranean rodentia to homosapiens that would be great...yeah...


While I don't recall making any claim regarding "subterranean", nevertheless, there's (Wiki, I know) this:

https://en.wikipe..._mammals

Indeed biscuit, all mammals --including Humans-- are descended from a small rodent-like progenitor.
bschott
not rated yet Aug 24, 2017
While I don't recall making any claim regarding "subterranean", nevertheless, there's (Wiki, I know) this:

You didn't. Again, in the context of the article they would have been the only survivors. And unlike a lot of people here I don't mind links to Wiki...although I have read the one you provided a few times in the past for various references. I only referenced "subterranean" because the post of mine that you responded to had the quote from Bendbob about mammals that live underground.
Cheers
Caliban
not rated yet Aug 24, 2017
While I don't recall making any claim regarding "subterranean", nevertheless, there's (Wiki, I know) this:

You didn't. Again, in the context of the article they would have been the only survivors. And unlike a lot of people here I don't mind links to Wiki...although I have read the one you provided a few times in the past for various references. I only referenced "subterranean" because the post of mine that you responded to had the quote from Bendbob about mammals that live underground.
Cheers


Hahaha!

Poor biscuit, reduced to a pathetic attempt to walkback an overstep.

No worries, biscuit.

I can certainly understand how, in your haste to ridicule, you took that one step too many.

Jeers!

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