Martian attacks may be more preferable than Venutian

That's right. Greek is a fun language (note the sarcasm), and so is Latin. It is certain that were we to be attacked by folks from Mars, we'd call them Martians, and from Venus, Venutians. However, if you follow the Latin rules for grammar, the "of Venus," genitive case would make those invaders Venereal.

As Neil deGrasse Tyson says in the book i'm currently reading, the misfortune is that doctors stole this term before astronomers could claim it. Proving once again that astronomy is only the second oldest profession.