Scientists believe they know which year the asteroid that killed all the dinosaurs collided with Earth.
- It is a combination of evidence that allows us to now say when it happened, says Melanie During, researcher at Uppsala University in Sweden.
According to the latest estimate, the asteroid that exterminated 76 percent of all species crashed into the earth 66,043 +/- 0.043 million years ago. There is thus an uncertainty of up to 86,000 years in the calculation. Despite this, researchers now believe they are sure that it happened during the boreal spring, that is, when it is spring in the northern hemisphere.
How come? One wonders. Melanie During, who works at the Center for Evolutionary Biology at Uppsala University and is the first author of the study now presented in the journal Nature, tells of a place in southwestern North Dakota in the United States, where there is an almost unlikely accumulation of fossils in what once was time was a lake.
- The place is called Tanis and there, at Hell Creek, we find lots of fossilized dinosaur teeth, shark teeth and fish. Everything is gathered in one place and most of all these animals died at the same time, just minutes after the impact, she says.
How do you know that?
- You can compare the impact with throwing a bowling ball in a sandbox. Enormous amounts of molten rock and soil were thrown into space, says Melanie During.
Once there, they solidified and formed small glass-like hollow bullets. After between 15 and 30 minutes, the bullets fell to the ground over large areas. Many of the animals that died and fossilized in Tanis were fish.
- These bullets are called tektites. Previous research has shown that they can only be formed in space. On Earth, they become completely flat, due to gravity. If you look at the gills in these fossilized fish, you see round tektites everywhere. They are not found in the digestive system, but only in the gills, which means that the tektites came right at the moment of death, says Melanie During.