What cataclysm wiped out the dinosaurs from the surface of the Earth? A dense interstellar cloud passing over the planet, say Japanese researchers! Their paper is published in the journal Gondwana Research.
The most popular opinion pertaining to the extinction of dinosaurs is probably the one about some impact event that caused the formation of the Chicxulub impact crater in Mexico. If this sounds far-fetched, wait till you hear the new theory proposed by a team of scientists from Japan.
The team led by Tokuhiro Nimura from the Japan Spaceguard Association puts forward the concept that the Earth passed through a dense interstellar cloud back when dinosaurs walked on it. This event would have led to a “Nebula Winter” that would have cooled the whole planet to such an extent that most life forms would not have survived. They came to this possibility after discovering a thick deposit of iridium in the Pacific Ocean.
This iridium layer is 5 meters deep. A similar layer, 30 centimeters in width, had been previously discovered and attributed to alien origin previously — it might have come from asteroids, for instance. As for the new one, Nimuro and his colleagues explain that it is too thick to have been the product of asteroid impact. Rather, the Earth might have passed through a 330-light-years molecular cloud that was specially dense (over a thousand times denser than the space around) — an event that would have dragged along for a considerable amount of time; the authors say that the global climate cooling would have happened in the “last 8 million years of the Cretaceous period”. During this phase, Earth would have undergone massive cooling and darkening, eventually resulting into the extinction of the dinosaurs 66 million years ago. The traces left behind of this event would be the iridium.
Can the Earth (and thus the solar system) actually pass through such interstellar clouds? While it is not proved, it has been suggested by other researchers before.
It is to be noted, though, that the team says both the interstellar cloud event and the asteroid impact might have contributed to the death and end of dinosaurs.