A Double Ringed Basin on Mercury . ... Credit Copyright: NASA / JHU APL / CIW Explanation: What created the internal second ring of this double ringed basin on Mercury? ... Since it is unlikely that a second impact would occur right in the center of the first, large double rings are usually attributed to a subsequent volcanic lava flow inside the impact crater . ... One clue to the origin of the above-imaged double ring is that the basin center appears much smoother than the region between the rings. ...