Just for the sake of saying, BigMac …
The "moon" isn't the one of two Oerth moons which is like "our" moon.
It's described as "An Alien Jungle", "woodlands", and "dense forest" with "nightmare greenery" and is "completely foreign". Further, it is "gloomy and grim" and "the [lavender] sky is almost entirely covered with angry blue-gray clouds shot through with huge branching lightning bolts" and when the sun can be seen, it's a "pale disk". There's a ring of mountains in the distance, if the PCs manage to get a vantage to see them, and the "horizon seems unnaturally close" (because it's a small planet.)
The rest of the planet is "mostly dry land, with oceans, seas, and lakes covering only about 30% of the surface area. The topography varies wildly, from rolling, grassy planes, through deserts, verdant forests, and rugged scrublands to jagged mountain ranges. Ocean depth ranges from shallow continental shelves to abyssal trenches and circular sinkholes—which might or it might not be the remnants of meteor craters—several miles deep."
As RipVanWormer points out, that base is in ruins. They are said to be "knee-high" and of a Perrendland architectural style.
The PCs really don't spend all that much time on Luna. It's something like 7% of the adventure. (5 of 64 pages), and they don't go very far, at all … only about a 1/2 mile to a mile, I think.
If a DM wanted to, they could certainly flesh out considerable amounts of not only the adventure site, but, the entire planet. Obviously, in SJR6 Greyspace there's a lot more detail of the planet, like it's flora, fauna, magnetic poles, rotational axis, lower O2, etc. But, there's no native intelligent inhabitants, but there's plenty of hostile animal and monstrous lifeforms.
I generally imagine it something like the planet "Pandora" from the movie Avatar, if you've seen that. Although, there's plant species found on Luna that are the same or similar to those found on Oerth, only larger and more overgrown.