* Astronomy

Ancient geologic conditions in southern Sweden were ideal to preserve meteorites that fell to Earth about half a billion years ago. Researcher Birger Schmitz (working as a visiting professor at Rice University and now at the University of Lund, Sweden) and his colleagues in Göteborg, Sweden have analysed over 40 of these rare fossil meteorites along with relict chromite grains collected from sites in a 250,000-square-kilometer area of 480-million-year-old limestone. They attribute the abundance and wide distribution of this space debris to a meteorite influx at least one hundred times more intense than the influx today. Rather than a smorgasbord of different types, cosmochemical evidence shows that the fossil meteorites are L or LL chondrites leading the team to conclude that these meteorites and chromite grains derived from a major collision in the asteroid belt. The age of the limestone is very close to the impact age of many L chondrites suggesting that this major collision was the breakup of the L chondrite parent body, possibly the largest impact in the asteroid belt in the last few billion years.
 
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