Extraterrestrial Impact Structure?

For a time, people believed that the Richart structure was the product of an extraterrestrial impact, such as an asteroid or meteorite. However, more research eventually revealed that it was not actually an impact crater, but instead a a circular anticline whose crest has been eroded away.

This huge structure of concentric circles was first seen by astronauts from space, and for a time, was believed by all to be the product of an extraterrestrial impact (such as an asteroid or meteorite) due to its remarkable symmetry. However, it lacked the melted rock typical of an extraterrestrial impact, and more research eventually revealed that it was not actually an impact crater, but alternating layers of sedimentary, metamorphic, and igneous rocks that were pushed upward in a symmetrical anticline, geologic dome, from below due to a small incursion of magma.

(What is an Anticline?)