The Survivors! New Theories About the Chicxulub Asteroid Impact 65 Million Years Ago
Follow the Daily Galaxy
Add Daily Galaxy to igoogle page AddThis Feed Button Join The Daily Galaxy Group on Facebook Follow The Daily Galaxy Group on twitter
 

« Snowfall on Ancient Mars? | Main | Quasars' Awesome Power Found to Extend to Outer Limits of Galaxies »

July 24, 2013

The Survivors! New Theories About the Chicxulub Asteroid Impact 65 Million Years Ago

 

           Chicxulub_sharpton_big

 

Evolution will adapt a given population more accurately to contain the knowledge needed to survive. A new study proposes that the biological adaptations some organisms evolved to deal with the challenges of living in freshwater environments also helped shield them from the months of frigid darkness that followed the impact of the large asteroid that crashed into present-day Chicxulub, Mexico, likely triggering a global firestorm and hurled huge amounts of vaporized rock high above the atmosphere 65.5 million years ago, killing off the dinosaurs.

The six-mile-in-diameter asteroid is thought to have hit Chicxulub in the Yucatan, striking with the energy of 100 million megatons of TNT, said chief author and Researcher Doug Robertson of the department of geological sciences and the Cooperative Institute for Research in Environmental Sciences.

In 1990, dramatic support for this theory came from cosmochemist Alan Hildebrand's revelation of a 65 million year old, 112 mile wide ring structure shown in the image above that is still detectable under layers of sediment in the Yucatan Peninsula region of Mexico. The outlines of the structure, called the Chicxulub crater (named for a local village), are visible in the above representation of gravity and magnetic field data from the region. In addition to having the right age, the crater is consistent with the impact of an asteroid of sufficient size (6 to 12 miles wide) to cause the global disruptions. Regardless of the true cause of the K-T event, it is fortunate that such impacts are presently believed to happen only about once every 100 million years. 

The "heat pulse" caused by re-entering ejected matter would have reached around the globe, igniting fires and burning up all terrestrial organisms not sheltered in burrows or in water, he said.  "The kinetic energy of the ejected matter would have dissipated as heat in the upper atmosphere during re-entry, enough heat to make the normally blue sky turn red-hot for hours," said Robertson.

Scientists have speculated for more than a decade that the entire surface of the Earth below would have been baked by the equivalent of a global oven set on broil. The evidence of terrestrial ruin is compelling, said Robertson, noting that tiny spheres of melted rock are found in the Cretaceous-Tertiary, or KT, boundary around the globe.

The spheres in the clay are remnants of the rocky masses that were vaporized and ejected into sub-orbital trajectories by the impact. A nearly worldwide clay layer laced with soot and extra-terrestrial iridium also records the impact and global firestorm that followed the impact. The spheres, the heat pulse and the soot all have been known for some time, but their implications for survival of organisms on land have not been explained well, said Robertson. Many scientists have been curious about how any animal species such as primitive birds, mammals and amphibians managed to survive the global disaster that killed off all the existing dinosaurs.

"[Freshwater] organisms are adapted to physical and chemical changes that go well beyond what marine organisms need to be adapted for," said William Lewis, a freshwater scientist at the University of Colorado. Many freshwater creatures are adapted to annual freeze-thaw cycles and periods of low oxygen when many of them go dormant by burying themselves or their eggs in the mud. "We do see some dormancy in the marine environment," Lewis added, "but it's unusual because it's not necessary for most organisms."

"I think before that most people had concentrated on the collapse of the food chain to explain why certain groups went extinct," said Alison Murray, a paleontologist at the University of Alberta in Canada.

"In this current paper, published online in the Journal of Geophysical Research—Biogeosciences, the authors are developing that food chain collapse, but in a more detailed manner, examining different groups and determining which might survive a prolonged period without light and the corresponding loss of the photosynthetic organisms," Murray, who did not participate in the research, said in an email.

In his earlier work, Robertson, showed that when the impact debris fell back to Earth a few hours later, it would have then reentered the atmosphere so fast that the heat of its descent would have caused the sky to glow red and tinder on the ground to burst into flames. "The radiation and fires would have been fatal within hours to everything that was not sheltered underground or underwater," Robertson said. "Dinosaurs all died within a few hours of the impact." The dust and ash still in the air would have darkened the sky and plunged the planet into an "impact winter" lasting months to years killing off plants and other organisms that relied on the sun's light for energy quickly died.

According to this model, the oceans were largely shielded from the initial burst of heat and fire, but soon after, entire groups of organisms, including the giant marine reptiles known as plesiosaurs and shelled, squid-like creatures called ammonites, became extinct when marine food chains collapsed.

About 20 years ago, scientists began to notice that the extinction levels among freshwater creatures were more subdued: Whereas marine environments lost as much as half of their groups of creatures, the freshwater extinction rate was only about 10 to 20 percent. Meanwhile, Fastovsky and Peter Sheehan, a paleontologist at the Milwaukee Public Museum and a co-author on the new study, observed that freshwater organisms are more accustomed to feeding off detritus, or dead organic matter. During the impact winter, freshwater environments would have received a steady influx of dissolved organic matter that was regularly washed into rivers and streams from dead plants and animals on land. Those same flowing water sources would have also kept freshwater ecosystems well oxygenated. However, the ability to enter dormancy in freshwater was probably more critical to survival, Robertson added.

The challenge now for paleontologists will be to figure out ways to test the hypotheses outlined in the paper. "That's the bugaboo," Fastovsky said.

Robertson belives that thinks the collapse occurred on similar timescales in both freshwater and marine environments, but that lakes and rivers recovered faster—but agreed that testing the model would not be easy because the evidence for the survival of freshwater ecosystems comes entirely from the fossil record found in a small area in Montana. "It will be both important and difficult to find similar evidence elsewhere on the planet," he concluded.

The Daily Galaxy via http://solarsystem.nasa.gov/news/display.cfm?News_ID=8396 and National Geographic

Image credit: courtesy V.L. Sharpton, LPI

Comments

Its pretty obvious, IMO, that the impact was a marine impact that caused global rainstorms, tsunamis, and a super greenhouse effect.

Sure there may have been substantial fire storms, especially around the regions where the impact occurred. But coastal tsunami flooding and torrential rainstorms probably quickly put most fires out.


Rainstorms would have also quickly washed out any dust in the atmosphere from the impact.

The fact that tropical animals like birds, crocodiles, turtles, and primates survived the extinction event pretty much tells you that there was no nuclear winter.

Marcel F. Williams

"The radiation and fires would have been fatal within hours to everything that was not sheltered underground or underwater," Robertson said.
My simple question is - were the birds underground or underwater? Maybe all birds died off, too, but the new generation came out many months or years later from the surived eggs.

This was a fascinating read! I did some more research afterwards and found out the explosion was equivalent of 100 millions of TNT. That can't be even comprehended by the human brain.

Interesting theory about freshwater vs sea creatures too.

I have a problem with the article saying the dinosaurs died off in a short time. They didn't. It was a sudden die off for some, slow for others, millions of years slow in fact. So not all of them died at once. I agree with the horrific effects the impact had overall not to mention quakes and tsunamis world wide from the ground and water effects, both but a world wide fire storm somehow doesn't seem "right".

The article does uphold the sudden uprise in mammal population and evolution since they burrowed underground and therefore were more likely to survive in more or less areas which weren't affected as much. If only a few mammal species survived it would have spawned evolution of many subsequent species.

Insects and spiders also would have survived in some places for both lay eggs which are more resistant than adult organisms and some eggs were underground as well. Larvas of insects underground would have had a greater chance of survival than the adult counterparts above ground as would anything underground including seeds and spores of numerous plants.

I can see where fresh water organisms could survive better than marine.

Remember however this article is about a PAPER written, not necessarily an overall proof sponsored by various research efforts over a period of time. It's an interesting article with interesting proofs alright and that's where science advances...out of the box thinking. Hats off to the researchers for daring to offer new material concerning the KT event.

The PT event article I just finished here also inoculated some thought on microbial cause for mass extinctions...caused by a "various scenerios" happening close enought together to create environmental changes which were not survivable by many species...a spike in extinctions.

Some contributers to extinctions have been suspected gamma ray bursts close enough and intense enough to compromise survival of many species, that combined with, say, Earth events, could offer a one-two quick combination punch effect, greater effect than one individual punch then another a million or two years later.

So when searching for causes of extinction events, one must check lots of things in lots of places...magnet pole shifts, isotopes of a number of elements in what layers of rock, astronomical events, impacts, places where, trace molecules/compounds that give clues, fossils, gobbs of data and just stuff, it's quite complex if done right. But there are enough doctorate theses and enough grant funded university profs and researchers who must continuously publish or they are fired and must teach high school or get another job, that a continuous flow of papers will eventually yield the truth of whatever.

http://www.scotese.com/K/t.htm is a global map at the time of KT, note how close continents were relative to today's positions due to plate tectonics, therefore the effects would have been more severe on at least land species such as land dinosaurs, than, say, if the impact had hit the present global structure of continent placements.


Post a comment

« Snowfall on Ancient Mars? | Main | Quasars' Awesome Power Found to Extend to Outer Limits of Galaxies »




1


2


3


4


5


6


7


8





9


11


12


13


14


15

Our Partners

technology partners

A


19


B

About Us/Privacy Policy

For more information on The Daily Galaxy and to contact us please visit this page.



E