The light spots are suspected of being ices or salts oozing up from the ground. It may not be water ice. It's cold enough there for methane or similar compounds to be liquid & freeze. Also, with almost no atmosphere, whatever the fluid is, would quickly evaporate leaving salts & minerals behind that were dissolved in the fluid. In the picture below, you can see slightly lighter patches when it may pooled, flowed, streamed in the crater.
Also in the picture, you can see near the top center of the crater wall where it appears to be collapsed & a mud flow seems to flow in. So this white stuff may also be oozing out of the flow, & flowing into the low spots of the crater. Another interesting feature is the dark spot on the opposite side of the crater, but no impact crater at the dark spot. So it's like a spray of dark material or dust sprayed out of the crater, & it fell back down there. It may also be plant or fungal growth fed by whatever is going on at or near the crater. Another interesting note is the spots appear to change shape & brightness over a few weeks, so whatever it is, it's an active area. That dark spot wasn't there a few weeks ago!