Lots of interesting information at ESA’s website here. This agency has a very friendly web presence with many beautiful images.
A long time ago a wonderful geomorphologist named Marie Morisawa taught me that round-headed gullies like this were groundwater driven, and apparently these were formed that way. These are called “sapping canyons,” a new term for me.
But these guys have other ideas, and think megafloods could carve such features. For possible Martian life, groundwater would probably be better than infrequent megafloods.
Photo credit: ESA/ DLR/ FU Berlin (G. Neukum)