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History shows that recent (in scientific terms) asteroid impacts have changed the face of the Earth. An iron-based asteroid about this size of 2012 DA14 blasted out Meteor Crater in Arizona which is about 4,000 feet wide and 700-800 fett deep. Another in 1908, hit Tuguska, Siberia. The asteroid that made the impact event, now know as the "Tunguska Event," was just slightly smaller than 2012 DA14, approximately 100 – 130 feet or 30-40 meters across. It destroyed about 750 square miles of forest in and around the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia.
Death to dinosaurs
Of course, we know what happened to dinosaurs. Earth's climate may have changed when a massive asteroid smashed into what is now Mexico's Yucatan Peninsula and triggered cooling temperatures that wiped out the creatures. The asteroid left a 110-mile-wode crater near Chicxulub, Mexico.
Missions to come
One of the biggest upcoming asteroid threats found is from 500-yard wide "1999 RQ36." It has a 1 in 2,400 chance of impacting Earth in the late 22nd century. NASA plans to send the OSIRIS-REx to land on the asteroid and take samples for further study. It is expected to launch in 2016, arrive in 2018, and work until 2021, then return to Earth with its findings and samples. Above is the sample collector.