Río Cuarto, Córdoba
In 1990, Captain Ruben Lianza of the Argentine Air Force, an amateur astronomer, provided a report to an astronomy publication that included aerial pictures of a set of odd teardrop-shaped depressions near the city of Río Cuarto, Córdoba in north-central Argentina. The depressions seemed very similar to the sets of craters produced in laboratory simulations of impacts taking place at low angles. Such features exist on the Moon, Mars, and Venus, but had not been seen on Earth up to that time.