Editing Río Cuarto craters (section)

== Discovery ==
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 [[Impact crater|crater]]s 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.

The depressions had long been known to Argentine geologists, but until Lianza, nobody had seriously investigated them. Samples of materials obtained from the depressions indicated the presence of shocked materials, as well as pebbles that were clearly of [[meteor]]itic origin {{Citation needed|date=September 2017}}. A team of [[United States|American]] researchers went to Argentina to investigate, collaborating with Captain Lianza and Argentine academics to study the strange depressions.

There were ten depressions, four of them of substantial size. One depression, named the "Drop", was about {{convert|200|m|ft}} wide and {{convert|600|m|ft}} long. Two more large depressions, the "Eastern Twin" and "Western Twin", both about {{convert|700|m|ft}} wide and {{convert|3.5|km|mi|frac=4|abbr=on}} long, were located {{convert|5|km|mi|frac=2|abbr=on}}  northeast. Another major depression, the "Northern Basin", about half and again as big as one of the Twins, was sited 11 kilometers further to the northeast. The long axes of the depressions all point to the northeast.