OK, I didn't think of that! Isn't it lucky for our intrepid crew that the starport was on the highest mountain and not a wide mountainless plain.
I think the assumption can be made that the Cocytans would refreeze their ice caps once they'd returned from ST6. They must have had a few years to think up a way to do it whilst there. So that means our previous conversation can still be valid.
As far as canon is concerned, I do now remember reading on the site about how the strategy guide was compiled, I was just not remembering when I asked the question. I really need a copy of the strategy guide, but until I get one, I'll keep putting my foot in it anyway.
So, what sort of problem could the Cocytans have that might require the return of the Earthlings?