The Earth has been impacted by asteroids, meteorites and comets 190 times since it was formed. Where are the biggest craters and what is their diameter? I found my answers in the Earth Impact Database maintained by the Planetary and Space Science Centre at the University of New Brunswick in Canada. They might be quite interested in this topic as Canada (or what was Canada millions and billions of years ago) has three entries in the Top 12 list! Luckily these events don't occur too often.