Free Astronomy Magazine January-February 2018

26 EARTH meteorites, it trig- gered an exten- sive series of fires in forests around the globe, produc- ing huge amounts of soot dispersed by atmospheric circulation and then returning to the ground in rainfall. Once the soot reached the ground, it settled in a geological layer that tells us the time of the impact (66,038,000 ±11,000 years ago) along with other materials, including sig- nificant quantities of iridium from the as- teroid. During its stay in the atmosphere, the soot prevented part of the solar radia- tion from reaching the surface, and this triggered a drop in the global average temperature, directly causing the mass ex- tinction at a point between the Cretaceous and Paleogene eras (K-Pg boundary). V isualization of the aster- oid impact that 66 million years ago killed 75% of living species on Earth. [R. Mi- chalik, D. Dolak, The Science Insi- tute Columbia College, Chicago] Below, a repre- sentation of the Chicxulub im- poact seen from space. [Joe Tuc- ciarone, Science Source] In addition to the immediate, apocalyptic aftermath of the impact on a regional and continental scale, the event also had catas- trophic effects on a planetary scale due to trillions of tons of material of varying con- sistencies and sizes thrown into the tropo- sphere, the stratosphere and beyond. According to the prevailing theory, when the heaviest part of that material plunged to the ground in the form of burning