A red tornado

'You have to understand that you need a regolith thickness of least 2.5 meters to protect the human body to a safe background level of radiation - I know I know, aliens, but you're going to be up there sometimes, and you said I could come and visit once. I may be dead, but I don't want cancer at the same time.'

Plus, burns.

'So no, you can't just use the stuff we have down here. And it'll need to be massively energy efficient, because of the cold. And are your aliens using their skills to build, or tools - because without air acting as a buffer on things like drills and mining equipment, the heat build-up will be insane, and break everything. It'll all just fuse together, and you'll get nowhere. If they use explosives - or I don't know, laser eyes - then any loose debris will be like bullets shooting around, and will break into any equipment or supplies or people you might have lying around. So I get that you don't want to tell me how they're doing their jobs, but at least tell me they're aware of this stuff or are prepared to learn about it.'

Because if they're not, woe betide any human who tries to live in whatever they make up there.