re: 4 X 1AU= snow limit
Interesting. How do we know that?
I'd be interested to read up on it. Or do we simply use comet outgassing around Jupiter as a measure of water's ice point in AU terms? If so, it may become a circular argument using a thing's characteristic to try to determine what determines its characteristics? Hopefully, there's other evidence outside of comets' coma formation? If so, I'd love to read up on it. :)