Hunh: do we think that "terra firma" belongs strictly to Earth? And if so, what would be the equivalent Latin for "the solid ground of Mars"? Given that I am definitely going with areology as against geology, because who wouldn't? (Except for SETI, alas: today's planetary scientists talk about the Martian geology etc, which doesn't make me flinch so much as sigh softly like the wind across the sands...)