Hail the Mighty Styrofoam

The other day was gorgeous-- bright and sunny, puffy cottonball clouds, a slight chill to the air when the wind blew but otherwise warm. This is a picture of the sky.

Ally and I were playing inside, making a mess of things, when we heard a strange sound up on the roof. Ping. Ping. Ping. Ping. Ping. Ping. Ping. Ping. Ping. Ping Ping Ping PingPingPingPing. . . Santa Clause and his reindeer dancing on stilts? We went outside to investigate, and this is what we found.

As if that weren't peculiar enough, this same thing occurred another three times that day. And the hail pellets felt like styrofoam but tasted like cotton candy. (Okay, so I was going to taste them until they felt so weird.) They stuck to my car and the shadowy places of our home for hours afterwards like a bad batch of aerated dippin' dots, refusing to melt. We live in such an odd place.
Do you think the pellets were nuclear-waste related and would've glown in the dark? I should've harvested them for further testing. I also probably shouldn't have let Ally play in them . . .