[cynwoody]

since the sun is the source of heat in our solar system, how could the interstellar ice melt prior to the creation of the sun?

Who said it melted?

It could have simply accreted as ice crystals, then waited for the sun to start up and melt it.

[piasa]

We can never know about the days to come
But we think about them anyway
And I wonder if I’m really with you now
Or just chasin’ after some finer day
Sub-lim-m-a-tion
Sub-lim-m-a-tion
Is makin’ me late
Is keepin’ me waitin’

[Cvengr]

Looks more like Pasta Sauce to me.