Dinosaur extinction may have been due to “impact winter”

Los Angeles Times : About 66 million years ago, a large asteroid struck Earth and wiped out the dinosaur population as well as many other species. Exactly how the extinction occurred has been the subject of much research. Now Johan Vellekoop of Utrecht University in the Netherlands and colleagues have proposed that the asteroid strike brought on an “impact winter,” during which dust and soot thrown up from the crash permeated Earth’s atmosphere and blocked sunlight from warming the planet. To try to gauge the temperature drop wrought by the asteroid strike, the researchers studied ocean-dwelling microbes that died and sank to the sea floor during the time immediately following the impact. Because the composition of their lipids indicates the temperature of the water while the microbes were living, the researchers were able to determine that there was a period of time just after the impact when the temperature of the tropical sea was anomalously low. The new method has proven to be successful not only for taking the temperature of ancient climates but also for being able to do so for relatively short-term events.