The latest images at NASA web site of the brightest area now dubbed 'spot 5' shows two main and several smaller distinct bright areas. One of the larger spots is on the side of the crater's central peak and the other near the rim with smaller spots scattered between.
In some images it can be seen that the region around this crater has several/many sub-parallell lineal valleys or ravines that I do not see in other areas. Also in some images it appears one ravine feature is more strongly developed and passes very close to or through the crater, possibly intersecting another linear feature at or near the crater.
It's probable that the combination of the impact with the linear features has created a pathway for warmer water from below to escape to the surface where it forms fresh, clean reflective ice.
I envisage a geyser field. But what is the heat source? No gravitational friction so; ?radiation from decaying 'hot' minerals? residual heat from formation?
Go Dawn!! you liddle bewdy!
Other less bright features may be smaller variations with more restricted pathways and some appear to be fresher craters with debris rays.