Australia’s Aboriginal people had long known about the crater near Wolfe Creek by the time an aerial survey identified it in 1947. Almost circular, Wolfe Creek Crater (also known as Wolf Creek Crater) is considered the second largest crater in the world from which meteorite fragments have been collected. Because of its excellent preservation, the crater clearly shows the classic features that result from a large meteorite striking the Earth.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite captured this image of Wolfe Creek Crater on September 22, 2006. The Australian Outback appears mostly in varying earth tones in this simulated-true-color image. Deep green indicates vegetation lining the winding stream west of the crater. A road leads to the crater’s rim, approaching from the south, then turning east. The crater itself appears fairly dark brown, but a bright white splotch occupies the crater’s center.
Wolfe Creek Crater measures roughly 880 meters (2,890 feet) in diameter, and the mostly flat crater floor sits some 55 meters (180 feet) below the crater rim and some 25 meters (82 feet) below the sand plain outside of the crater. At the crater’s center, the ground rises slightly, and includes gypsum—probably responsible for the bright white spot in this image—and some surprisingly large trees. The trees likely draw moisture from the crater’s water reserves that remain after summer rains.
Geologists studying the crater have estimated that it formed some 300,000 years ago when a meteorite weighing more than 50,000 metric tons struck the Earth at an estimated 15 kilometers (9.3 miles) per second. Geologists conclude that besides punching a hole into the Earth’s surface, the impact shattered rocks well below the ground surface, and the energy from the meteorite’s rocket-fast movement changed into heat, liquefying both the meteorite and the nearby terrestrial rocks. The resulting explosion threw rocks and debris in every direction. Some of the rocks remaining in the crater now result from the meteorite itself. These rocks now take the form of rusted balls of iron-shale. Occurring in clusters, these balls can weigh as much as 250 kilograms (550 pounds) apiece.
NASA image by Jesse Allen, based on data provided by the USGS Land Processes Distributed Active Archive Center. Caption by Michon Scott.
Wolfe Creek Crater is the second largest crater in the world from which meteorite fragments have been collected. Because of its excellent preservation, the crater clearly shows the classic features that result from a large meteorite striking the Earth.
Germany’s Ries Crater (or Nördlinger Ries) is not easily discerned in space-based images. The crater’s existence was probably just as subtle to the medieval Europeans who established a settlement inside it and unknowingly matched their 1-kilometer- (0.6-mile-) wide city to the likely diameter of the meteorite that formed the crater.
Deep in the Sahara Desert lies a crater. Nearly a perfect circle, it is 1.9 kilometers (1.2 miles) wide, and sports a rim 100 meters (330 feet) high. Modern geologists long debated what caused this crater, some of them favoring a volcano. But closer examination of the structure revealed that the crater’s hardened “lava” was actually rock that had melted from a meteorite impact.