I don't know if he was ever a scientist. He was certainly a science journalist and planetarium manager. He was very good, too. A scientist? No, not formally. But perhaps in spirit.
The Face on Mars is a joke, not for the purpose of having fun and playing with the gullible, but for encouraging people, meaning Congress and NASA, to let us all share in the exploration of our solar system.
Hoagland's subspace or hyperspace physics, or whatever title he gives it, is not his, he is the journalist. Although the mathematics of the day was not up to the task of dealing with the idea, it may come back, probably in an altered form suitable for computer modelling. Along those lines stay tuned for developments of the fifth dimension out of Princeton and watch for Nima Arkani-Hamed, who may have something to say later.
Speaking of Nima Arkani-Hamed, I had the pleasure of showing him around the physics department here at Penn a couple of weeks ago, when he was the colloquium speaker. His talk was entitled "Deconstructing Dimensions" (in an intentional jab at postmodern blather). While he's famous for proposing that there exist large extra spatial dimensions, in this talk he was talking about eliminating dimensions! The subtitles of his talk were "Extra Dimensions Suck" and "Destroy All Dimensions".
He's come up with a way in which field theories can dynamically generate "apparent" or "effective" extra dimensions that behave so much like the real thing, that the possibility can't be ruled out that there are fundamentally fewer than the four dimensions we believe ourselves to live in.
He even had some experimental tests that could distinguish between real dimensions and "theory space" dimensions. First we have to discover the graviton, though.