Note: I wrote this article about 3 years ago. The numbers and theories are subjected to change as new data comes in.
As of August 2011, 8.7 million species (give or take 1.3 million) survive on this wonderful pale blue planet of ours. Fighting to survive against the odds of being hunted or caught in a natural disaster. Today, human beings have dominated this planet in every aspect. Empowered with amazing technologies, we can survive almost anywhere on this planet. Where the blue whales rule, deep in the ocean, we took our high resolution cameras and shot their routines. Where the penguins huddle up in groups to warm their bodies in negative temperatures (in degree celcius), we have set up research camps. Where the complex net of species survive in rainforests of Amazon, we have made science fiction movies. Needless to say, today this planet belongs to human beings. But this wasn't always the case. Some time in past, till about 66 million years from today, creatures with sized ranging from small to gigantic, both herbivores and carnivores existed on this planet and ruled.
Dinosaurs fascinate me. Partly because of Steven Spielberg, partly because it's the closest creature to dragons that really existed and partly because of the coolest things that paleontologists get to do. Dinosaurs existed on this planet from about 200 million years ago (the start of Jurassic period) up until 66 million years ago (end of Cretaceous period).
Scientists have collected the fossils from all around the world that strongly supports what I just said. But there was a mystery: dinosaurs were so powerful that it should have been impossible for mammals like us to have evolved alongside them. How did that happen? What caused the end of an era of those huge creatures?
Paleontologists and geologists study the Earth and the remains of the lost worlds by carefully examining the rocks. That’s what they do! It is, however, a matter of practice to differentiate between a fossil and a rock. After millions of years, bones lose their minerals and tend to look almost like rocks. In 1981, scientist Luis Walter Alvarez put forth his theory of a large body impact on Earth, based on the evidence he found in rocks. He found that there was a layer of clay consisting iridium and shocked quartz radioactively dated about 66 million years ago. Iridium is one of the rarest elements on Earth. It was hardly plausible to find it uniformly in a layer dated about 66 million years ago. But guess what contains iridium in rich content - extraterrestrial bodies, asteroids! This was his first clue. The second clue was shocked quartz. Shocked quartz are special type of quartz that is only created after a huge amount of pressure. The layer in the quartz gets deformed by the pressure. And exactly how much pressure is needed to do that? Well, even a volcano eruption can not deform a quartz! The first shocked quartz was found in underground nuclear bomb testing. So to deform a plane in quartz, you need energy compared to nuclear bomb! This kind of pressure can also be created by a fairly big asteroid impact. Now Alvarez had formed his theory. But he lacked the most important thing - the crime scene - the crater. He was in search of a crater that might have been created by such huge impact.
Let's go back to 1978. Geophysicists Antonio Camargo and Glen Penfield had found a gravity potential map with a curious ring of about 70 km across at gulf of Mexico. They were working for an oil company Petroleos Mexicanos. Penfield then dug deeper in published papers. He found a similar gravity map that was obtained a decade ago, but wasn't published due to corporate policy back then. Penfield then published his results and possibility of a geological even near the gulf of Mexico in a conference. But he didn't get much attention. Scientists were busy in attending conferences on Earth impact elsewhere in the world.
Later in 1990, a reporter for Houston Chronicles told a scientist about Penfield's discovery. Then the search for more evidence led to the conclusion that indeed an extraterrestrial body had hit the Earth near gulf of Mexico about 66 million years ago. Finally, the crime scene was found! Recent findings show that the crater created by asteroid is about 300 km wide. Due to it's geography, it's named 'The Chicxulub Crater'.
However, it is still hard to believe that one asteroid strike wiped out the dinosaurs across the planet. So let's see what might have happened after the asteroid strike.
The estimated size of the asteroid that hit Earth is about 10 km or more. The resulting energy due to impact is estimated around 240,000 gigatons of TNT (FYI the 2004 Indian Ocean earthquake that led to tsunami had an estimated energy of 9560 gigatons of TNT. 240,000 gigatons of TNT is about 8 billion times stronger than energy released by each atomic bomb dropped on Hiroshima and Nagasaki). This was A LOT of energy. Far more powerful than any major event in history of Earth for hundreds of millions of years. Such amount of Energy would power today's world for hundreds of years. But still, it wasn't enough to kill every dinosaur on Earth. It would, however, roast every living being present within 100 km radius instantly. What killed dinosaurs wasn't the impact, but it's after effects.
The impact caused huge amount of heat released in atmosphere. Saying that it might have caused fireballs thrown around as far as 200 km would not be an exaggeration. This impact must have caused a huge shock wave that spread around the half of the globe. It caused many largest mega tsunamis that Earth has ever seen. It released a huge amount of hot ash and gas that later covered almost the globe. This led to climate change. It brought some of the hottest years on Earth. It wiped out vegetation in huge areas. Herbivores didn't have much to eat, and so carnivores fell short of herbivores. The impact must have released huge amount of sulphur and carbon dioxide in atmosphere. Carbon dioxide will be balanced after many years. But sulphur stays longer. So first, it was a global warming, caused by carbon dioxide in atmosphere. And later, it was mini ice age, caused by sulphur. Animals as big as dinosaurs would not survive such impact and it's after effects. The only species that had a chance at survival were those who stayed close to ground, or even underground - mammals. After hundreds of years, Earth started to glow again, in the light of living beings that ultimately led to existence of human beings.
Chicxulub impact was HUGE. It was a hell on Earth. But ironically, we owe our existence to it.Further reading:
[1] Wikipedia page for Chicxulub crater and related expedition
