The total amount of dust, they calculated, was about 2,000 gigatonnes - exceeding 11 times the weight of Mt. While prior research highlighted two other factors - sulfur released after the impact and soot from the wildfires - this study indicated dust played a larger role than previously known. "It was cold and dark for years," Vrije Universiteit Brussel planetary scientist and study co-author Philippe Claeys said. "While the sulfur stayed about eight to nine years, soot and silicate dust resided in the atmosphere for about 15 years after the impact. "Without the impact, my guess is that mammals - including us - had little chance to become the dominant organisms on this planet."

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Persons: grâce, Cem Berk Senel, Philippe Claeys, Özgür Karatekin, Karatekin, Claeys, Will Dunham, Rosalba O'Brien Organizations: Royal Observatory of, Vrije Universiteit Brussel, Nature, Dinos, Thomson Locations: North Dakota, WASHINGTON, Yucatan, Everest, Dakota, Royal Observatory of Belgium, Vrije, Belgium