Assistant Professor Jason Moore and three students from the University of New Mexico Honors College are heading to Uruguay this summer to search for more clues in the riveting and ongoing account of what vanquished the dinosaurs and 75 percent of all animal and plant life 66 million years ago.
The commonly accepted theory for the mass extinction is that a six mile wide asteroid struck what is now Mexico 66 million years ago. The 110-mile wide prehistoric crater lies 12 miles beneath the Yucatán Peninsula near the town of Chicxulub, after which the crater was named.
The impact triggered massive environmental change and caused food chains to collapse on land and sea, ultimately contributing to the demise of the dinosaurs.
The theory was first posited in 1980 by Nobel-winning physicist Luis Alvarez and his son, geologist Walter Alvarez. While the younger Alvarez was conducting research in Gubbio, Italy he found in a thin layer of rock high concentrations of the metallic element, iridium. Iridium is rare on Earth but rocky space debris such as asteroids contain high amounts of it. The layer of rock lies at the K-Pg boundary which separates the age of the dinosaurs (Cretaceous) from the age of the mammals (Paleogene). The K is from the German spelling of Cretaceous. There are over 350 places on Earth that exhibit rocks that span this boundary.
“The current consensus in the scientific community is that an asteroid, about six miles in diameter, hit the earth traveling relatively slowly, six to 12 miles per second," Moore said. "But when my colleagues and I looked at these numbers, they didn’t add up. Because we know the properties of asteroids rather well, and we know the amount of iridium there is in a small chunk of asteroid, we can extrapolate how much should be in a six-mile wide asteroid. And our calculations found that there was too little iridium and osmium, another element common in space rock, at the K-Pg boundary.”
Consequently, Moore who is also an adjunct professor in UNM's Department of Earth and Planetary Sciences, agrees with fellow scientists that Chicxulub was the impact zone, but disagrees that the cosmic culprit was an asteroid. He proposes that it was a comet. “Comets travel faster than asteroids, and contain ice in addition to rock, so a high-velocity comet would have sufficient energy to create a 110 mile wide crater, but would leave much less iridium on the Earth’s surface,” Moore said.
Taking it a step further, Moore shares an emerging theory with a growing number of scientists, that the dinosaurs were actually destroyed by two simultaneously occurring events that happened at the end of the Cretaceous age: an enormous terrestrial impactor, in this case Chicxulub, and an apocalyptically large volcanic eruption from the Deccan traps of India.
“The eruptions were larger than anything we can imagine,” Moore said. “Here’s a series of volcanoes blasting out into the atmosphere huge amounts of carbon dioxide, sulphur dioxide and also changing the landscape of India. It would have resulted in massive global climate change and ocean acidification. Then add to that the impact from an enormous space rock crashing into Earth at tens of kilometers per second. That’s a combination of catastrophic proportion on both a local and global scale.”
When asked what research was taking him and his students, Caitlin McGuire, Conor Kantrowitz and Alison Turner to Uruguay, Moore said that a group of scientists from the Universidad de la República (UDELAR) in Montevideo had published papers suggesting that rocks in the northern part of the country contained preserved fossils that could span the K-Pg. Moore and the students will be working with two paleontologists from UDELAR looking for remnants of the Chicxulub impact, as well as dinosaur eggs and nests, among other things.
“There’s great potential to take our knowledge of these kinds of systems that exist outside of Uruguay and collaborate with our colleagues to pin down if they are of the right age,” Moore said. “And of course, we’re hoping to find more data to further test our hypothesis of comet vs. asteroid, and figure out the global effects of the Deccan volcanism.
“I believe the comet plus volcanism hypothesis is the one that best explains everything we’ve seen around the globe so far, but as a good scientist you always want to test and retest your hypothesis. It’s a big question mark, and the Uruguay project will provide a new window through which we may see something completely different.”
Uruguay is the next stop in the journey toward discovering what ultimately killed the dinosaurs. The last stop will require a complete record, because according to Moore, “an incomplete record is like trying to understand the evolution of music having only Bach and the Beatles. You have to have everything in between so you can see how and why all the changes occurred.”
Funding for the Uruguay project is provided by a grant for international research to the Honors Research Institute from Sonnet and Ian McKinnon.