I'd say that there had been some compaction or subsidence and the icy layers have settled over the trace of a buried crater, leading to the chracteristic double fault trace of a circumferential graben over the crater rim.

Now it's interesting that this has happened - it suggests that something has caused compaction. Maybe a mild thaw, maybe a sub-ice volcano.

Probably this all happened a while back and we're seeing the trace of things picked out by differential erosion of the ice, but it can't have been too long ago or those spiders and other dynamic topographic forms would have obliterated it. I'd guess a few tens of thousands of years ago, but I'm just guessing...