Perched at the edge of an outflow channel, these two craters appear to have lost a portion of their crater rims during a flood event.
Alternatively, it is also possible that the craters impacted the edge of the outflow channel after the flood occurred and we are seeing the difference in the strength of the material impacted.
Written by: Candy Hansen (audio: Tre Gibbs) (21 August 2017)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_050746_1775
Image: NASA/JPL/University of Arizona