Today's Image of Mars is from HiRISE and shows gullies on a wall in Bamberg Crater. The gullies appear to be more recent features because they don't have extensive debris aprons. There is also very little material accumulation on the crater floor, which is in contrast to most craters with gullies. These two observations seems to point to the gullies being relatively young features. There could be other explanations for this, but our knowledge of gully formation on Mars is incomplete and more observations are necessary for better interpretations.
Clicking on this image will take you to the original, captioned image from HiRISE.