New Data from a Round, Deep Basin in the Russian Heartland: The Smerdyachee Basin as a Prospective Impact Crater

We studied a proposed impact site: the circular Smerdyachee Basin. This consists of Lake Smerdyachee in its center, which is ~255 m in diameter. The lake is surrounded by a continuous raised rim, ~409 m in diameter (range: 404–414 m). To the SE, we found a 3% Ni spherule inside a Ni-rich rock along with scattered angular Paleozoic rock fragments 10 to 30 cm in diameter. The latter appear only on one third of the rim and come from at least 40 m depth. These features – a continuous raised rim, Ni-bearing rocks, and asymmetrical excavation of basement rocks – are typically associated with impact craters. Modeling suggests the basin formed from the impact of an iron meteorite ~ 18 m wide that produced minimal shock melting or projectile vaporization. Fragments of a hypothetical iron meteorite should lie within a 179 by 126 m ellipse under Lake Smerdyachee. In the future, retrieval of projectile fragments and subsequent microprobe analyses of their composition would constitute more compelling evidence for an impact origin.