Free Astronomy Magazine January-February 2018

JANUARY-FEBRUARY 2018 D ramatic scenes of the end of dinosaurs, follow- ing the event of Chicxulub. In the view above, a few days have passed since the impact. In the one below, a few years have passed, and the mass extinction is complete. This general picture of the Chicxulub event and its consequences is broadly shared by an overwhelming majority of scientists, al- though some specific aspects could be in- terpreted differently. This is the case with a study by Kunio Kaiho (Tohoku University, Sendai) and Naga Oshima (Meteorological Research Institute, Tsukuba) recently pub- lished in Scientific Reports . The two re- searchers claim that the widespread fires in vegetation triggered by the burning material falling back to the ground cannot have generated enough soot to create a significant global drop in temperature. Moreover, the fires certainly affected every continent, so the distribution of soot in the atmosphere had to be fairly uniform, while there is evidence that indicates a more severe cooling in the northern hemi- sphere and a faster return to normal in the southern one. Above all, forest fires would have emitted soot only into the tropo- sphere, where its stay would have been slightly limited — perhaps weeks — before it was totally removed by rainfall. Such a short period of darkness would not have