17. Gosses Bluff Meteorite Crater, Australia
Lying just south of the Tropic of Capricorn and to the west of Alice Springs, Gosses Bluff Crater in the Macdonnell Ranges stands out as a prominent circular feature. All the terrestrial planets experienced an early episode of massive asteroidal bombardment, and many of them, for example, the Moon, retain a clear record of that bombardment. Normal processes of erosion have erased all trace of this catastrophic episode in the Earth's history. Only a small number of younger impact craters are known to exist and Gosses Bluff is one of these. The original crater was about 20 kilometers (12 miles) in diameter. The rim can be detected on close scrutiny of the photograph, but the eye-catching circle of sandstone was uplifted by the impact to form a central ring in the crater and is about 3 kilometers (2 miles) in diameter.
Most of the known impact craters on Earth are located in North America. This is because the continent contains large areas of ancient rocks — old enough to preserve a long record of impacts — and also because the continent has been minutely studied by geologists. Australia also contains large areas of ancient rocks but has been less closely studied. It is likely that several other major impact sites will come to light with further research.
STS-41D, August-September 1984. Picture #14-41-028.