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....[A]t this time – roughly 12,800 years ago, according to a new study from the University of Kansas – that a comet struck our planet and triggered massive wildfires. This impact also triggered a short glacial period that temporarily reversed the previous period of warming, which had a drastic affect on wildlife and human development. ... ...[T]he team combined data from ice core, forest, pollen and other geochemical and isotopic markers obtained from more than 170 different sites across the world. Based on this data, the team concluded that roughly 12,800 years ago, a global disaster was triggered when a...

A newly examined ice core shows what may be the chemical traces of supernovae that exploded a thousand years ago. Yuko Motizuki of the RIKEN research institute in Wako, Japan, and colleagues analysed the nitrate content of an ice core drilled at Dome Fuji station in Antarctica. Nitrate is produced in the atmosphere by nitrogen oxides, which in turn should be created by the gamma radiation from a supernova. Motizuki's group found high nitrate concentrations in three thin layers about 50 metres deep. Because snow gradually builds up into layers of ice, depth indicates age. After calibrating this icy calendar...