Every five-year-old and older knows the story of the asteroid that wiped out the dinosaurs 65.5 million years ago; but perhaps not as many know that scientists have also determined exactly where it landed — the Chicxulub, Mexico. There are no 65 million year old eye witnesses, as far as we know, so how exactly do they know where it landed?
The short answer — Iridium.
What is Iridium?
Iridium is a metal found in two places: asteroids and everywhere else. On the surface, that doesn’t seem all the helpful, but that’s actually kind of the point. Iridium doesn’t really hang out on the surface. It’s really dense and really heavy. So when the planets were still molten, all of the Iridium sunk down deep into the earth’s core, where it is likely to stay.
So imagine the conundrum when, in 1980, geologists discovered a layer of the earth’s crust that was flushed with the metal, nearly hundreds of times greater than usual. The same occurred in samples taken from matching layers all over the world.
What Does Iridium Have to Do With Dinosaur Extinction?
Nobel-prize winning physicist Luis Alvarez proposed the idea of a large asteroid impact as the cause for the “misplaced” Iridium. Due to its weight, any Iridium not located in the Earth’s core must have arrived after the Earth had cooled. The scientific community agrees that asteroids are one of the only ways for more Iridium to have been deposited since then, and perhaps the only method capable of sending the element flying all around the globe at around the same time.
This was further corroborated by the large number of additional impact sites discovered in the same sediment layer (i.e. time period), which astronomers confirmed to be from falling asteroid debris after the initial impact. This layer occurs at what is called the “Cretaceous–Paleogene boundary.”
Later on, other scientists built on the work of the Alvarez impact hypothesis and calculated the size an asteroid would need to be in order to accomplish a global extinction event, and determined it to be 10 kilometers in diameter.
To put this into perspective, the absolute deepest the ocean gets is 11 kilometers, so it would be the equivalent of throwing Manhattan at the Earth from space. This would leave a crater of about 100 kilometers, assuming you threw it from space at 30 km/s. The impact would have vaporized both a large portion of the earth where it landed and most of the asteroid-turned-meteorite itself, sending bits and pieces of the same sailing around the globe in a big life-extinguishing blast.
This second group of scientists were able to find such a crater, of just the right age and size, at the edge of the Yucatan Peninsula near the town of Chicxulub.
Currently, there are very few samples of the crater itself since it was discovered.
2016… Time to Prove Old Theories Right
In spring 2016, Sean Culick, a researcher at the University of Texas at Austin Institute of Geophysics (UTIG), and Joanna Morgan, of Imperial College London, will head down to Chicxulub, Mexico, with a team of scientists to drill 5,000 feet (1,500 meters) below the crater’s surface, which is currently covered with millions of years worth of sediment and ocean water.
These will be the first off-shore core samples ever taken. If the potential for new information about what ended the reign of the dinosaurs and human life that began after the impact wasn’t exciting enough, the team will also be looking for data on two more distinct subjects:
- First, scientists will be studying the impact itself to learn more about impacts in general and one of this size, which can tell us more about other impacts on earth, as well as other planets.
- Secondly, researchers will be analyzing the area for evidence of the sea life that existed in the immediate recovery post-impact. First density readings show that much of the terrain at the core is porous and likely could have served as a shelter for sea life in the area that was capable of surviving in the extreme temperatures.
Since Chicxulub is the only impact crater on Earth linked to a mass extinction event, scientists will now have the opportunity to learn more about the universe surrounding our planet, find more aspects that we have in common with other planets, and perhaps, ultimately, the keys to the mystery of life’s origin on earth.
“Planetoid crashing into primordial Earth” by Don Davis (work commissioned by NASA) / Public Domain, CC License via Wikimedia Commons
“Chicxulub-animation” by David Fuchs / Licensed under CC BY 3.0 via Wikimedia Commons
“Yucatan chix crater” by NASA/JPL-Caltech, Original modified by David Fuchs / Licensed under Public Domain via Wikimedia Commons –