Voyager.

Floating through space now somewhere is the voyager space craft. And on the side is this picture to show any aliens what we look like. And we're naked. Is this the first impression we want to give? They might be impressed by the technology, but they'll be picturing our scientists building it naked. There's also a record with some Beethoven on it (that's just wrong anyway- a space ship with an LP, it's like having a car with a sundial.) But even if they're impressed by the music, they'll be imagining the whole orchestra in the nuddy. And the record, to make sure it doesn't warp or rust, is made of solid gold. That's just dangerous. Aliens think we're so rich we make our LP's out of gold, and we flounce about in the nude - We're just asking to get mugged.

So aliens will expect us to be nude. But we expect aliens to be nude, when the little grey men come out of the space ship they're allways nude. ET was nude and that's for kids. Why? Who invents intergalactic travel before pants?