THE dinosaurs couldn鈥檛 stand the heat, and a very long deep freeze wiped out almost all other animals. These are two new takes on the aftermath of an asteroid impact 65 million years ago.
Following the impact, the sky would have glowed red for hours as debris rained into the atmosphere, broiling everything on Earth鈥檚 surface. Only animals that were able to find refuge would survive the heatwave, says Doug Robertson of the University of Colorado in Boulder. Dinosaurs and pterosaurs died because they were too big to hide from the burning sky. But mammals, birds, crocodiles, snakes, turtles and amphibians could hide underground or in the water (Geological Society of America Bulletin, vol 116, p 760).
After the sky cooled, dust blocked light from the sun, causing an 鈥渋mpact winter鈥�. It was previously thought to have lasted about a decade, but Matthew Huber at Purdue University in West Lafayette, Indiana, and his colleagues have come to a different conclusion. They analysed sediments that would have been around 200 metres deep in the ocean at the time of the impact.
Advertisement
The samples show that cold-water microbes invaded tropical waters for some 2000 years after the impact (Geology, vol 32, p 529). That suggests the impact winter lowered ocean temperatures by about 5掳C for two millennia, wiping out many marine organisms.