by BETSY MASON
Asteroid impact craters are among the most interesting geological structures on any planet. Many other planets and moons in our solar system, including our own moon, are pock-marked with loads of craters. But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact structures don’t last long and can be tough to come by.
But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here show some of the biggest, oldest and most interesting impact craters on the planet.
Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent unidirectional wind. The image above was taken by astronauts in the International Space Station in July. The radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.
The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
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