https://en.m.wikipedia.org/wiki/Robert_Reiner_(businessman)
More a local celebrity in his birth place than like real a class celeb. Howevery, he’s the reason why I got to sign the golden book of my home town when I was 10something. I still wish I had a good Signature back then and not just plain (and ugly) cursive.
TL;DR
Of course no spider aliens as the clickbait might insinuate.
These are cracks in the ice sheet caused by gases which when released to the surface bring dark material with them is spread on the ground in that manner.