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140 impact craters with diameters of 200 km or more are known on the Earth. They formed by impacts of cosmic bodies. Earth should have many more impact craters, like the Moon.But unlike the Moon, Earth has intense geological processes which erase the traces of cosmic bombarding on our planet. When a cosmic body collides with the Earth, the impactor's gigantic kinetic energy is expended, forming a crater and breaking, melting and evaporating the target material. These processes lead to formation of unusual rocks, called impactites, which have clear identifying features caused by the immense temperatures and pressures they have undergone. Large impact events - those which form craters of 100 km or more in diameter - could lead to global climate changes by filling Earth's atmosphere with dust. Many scientists think that the great Mesozoic extinction, including the extinction of the dinosaurs, resulted from the collision of a large cosmic body with the Earth.
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Smerdyachee Lake, perfectly round and 350 m in diameter, is located in Shatura region, 140 km east of Moscow. Smerdyachee is different from numerous other round lakes near Moscow because of its unusual depth (40 m) and its high, mounded, wall-like sides. Based on Smerdyachee's depth, near circularity, and its mounded wall, and
analysis by N.A. Fillin
of nearby Roshal, Russia, the Estonian scientists Yu.V. Krestlane and K.H. Mella proposed in 1987 that Smerdyachee Lake is a meteorite crater. However, no other facts supporting this idea were presented.
In 2002, the Laboratory of Meteoritics of the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences explored this mysterious lake. A preliminary study of rock samples collected at Smerdyachee Lake demonstrated that impact melt of local sedimentary rocks is present. This suggests that the Smerdyachee lake is indeed a meteorite crater. Calculations suggest the impactor had a diameter of 14-20 m and a mass of 11-13 thousand tons. The impact would have caused an explosion equivalent to 250 kilotons, 10-15 times the size of the Hiroshima atomic bomb. The 2002 investigation discovered fragments of basement rocks within the lake wall. The basement rock in this region is covered with a thick layer of sandy deposits and has no outcrops on the surface. This suggests that Smerdyachee was excavated to its depth of 40 m by an impact explosion. Based on preliminary data, the Smerdyachee Lake crater was formed approximately 10 thousand years ago. Thus, Smerdyachee Lake, a unique natural monument, may be the closest meteorite crater to the city of Moscow.
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