The reason why craters are made on Earth is because, when these chunks of rock pass through the atmosphere, they are too large to be slowed down and smash into the surface at a velocity of around 7.5 to 12.5 miles per second. These solid pieces of debris that have broken off from asteroids or comets, called meteorites, often create impact craters on the surface of terrestrial planets and moons.
Two types of crater are often made by debris that crashes through the Earth’s atmosphere – some are bowl-shaped, whereas some are of similar appearance but contain a raised central peak along with a risen rim which appears as a ring-shaped structure from a bird’s-eye view. However a meteorite doesn’t have to be large to make a great impact – the Barringer Crater in Arizona (pictured above), which has a diameter of almost a mile (1.6 kilometres) across, was made by a chunk of space rock about 0.02 to 0.03 miles (30 to 50 metres) in diameter. It is the speed of these pieces of rock that determine the crater’s size. But that’s not all.
The angle at which a meteorite impacts the ground, as well as the type of material it smashes into, are important factors. By studying impact craters, planetary scientists are able to piece together how the crater happened. In fact, simulations have been made that investigate such a scenario – LCOGT and Faulkes Telescope’s Impact Simulator or Purdue University’s Impact Earth are such examples. Give them a try!
Image credit: Shane Torgerson