Max: That massive flow could be lava but I think it is almost certainly glacial, and likely ice buried under a several feet thick layer of debris to protect it. Remember, this is at 34 degrees south latitude, where such glacial features appear quite common.

Make sure you look at the context image on the main image page for this cool image. Make sure also that you both zoom in and out to get a sense of the entire surrounding terrain. This location is not only at the right latitude, it is also at a relatively high elevation for the cratered highlands, increasing the likelihood that the glacial ice here is still present.

Just below it there’s another crater that had a wall collapse (south side) and it drifted across the crater and is still visible. Not as much liquid sediment material breached into the crater by evidence of the higher walls.
Below that, just outside of the picture is a large violent impact crater that has ejector markings radiating lines from the right side of the picture to the left which looks beautiful and fascinating.

On the original extreme close-up tadpole picture, there are numerous circle shadows in the landscape at top (with drainage channels flowing out of them) and mostly bottom of the picture. Are these windows? Some of them are just shadows by evidence of the brightness on one side but the others look like caves. If water evaporate from beneath the surface, old ice fields like this could be very dangerous to cross having voids beneath them.