As noted in the text, this set of gullies featured in a magnificent falso colour high-resolution MOC image on the cover of Science along with Malkin and Edgett's original "gullies" article.

What was not tghen clear, b ut is blindingly obvious in this larger-coverage "context" image is that the gullies do not emerge from hollows in the crater wall, but are positioned on promontories - quite the wrong place for groundwater to escape.

There is general concencus in the Mars community that a snow-thaw model for gully formation is much more plausible than groundwater escape.

OTOH, there are many flavours of thaw model, ranging from the original Forget/Lee/Hartmann models of season melt of water ice ("snow"), through Christensen's long-delayed melting of "fossil" snow through to my own CO2 snow thaw models.

There is more work to be done, of course, but few authors seriously imagine groundwater exists in the shallow subsurface of Mars.