Need advice on science/nature study with 6yo

Ok, I need a little bit of advice with my 6yo. We are a pretty outdoorsy family; we live on 14 acres, own some animals, like to go hiking, camping, swimming in the lakes during the summer, etc. My two older boys 12 and 7 LOVE the outdoors but my 6yo doesn’t particularly care for it. He would rather stay inside all day and play with Legos or listen to audiobooks/dramas. Of course, I make him go out and play and he usually has a fun time once he’s out but he wouldn’t choose it on his own. 

The “problem” so to speak is that he’s not really interested in nature and as a CM mom, I don’t know what to do with this. 😉 He will go on nature walks with us as a family and sometimes I can get him to help me “look” for birds or bugs and such, but he’s not really interested in them. He thinks the Thornton Burgess books (that my 7yo LOVES) are “boring” and has almost no interest in any kind of animals. He enjoys being read to (we’re in the middle of Pinocchio right now and he loves it) so I know it’s not just the reading part, he just genuinely thinks that books about animals, birds, etc. are boring.  

Now the other day I started gently probing and discovered that he IS interested in learning more about the human body or outer space. 

So I guess my questions are twofold: 1) Can enjoyment of the outdoors and nature be gently developed in a child who seems to have been born with an aversion to it? and 2) Are there living books that address the subjects of anatomy or outer space appropriate for his age? I’ve been looking at Apologia’s Elementary series but I’m worried that those might be a little too much for him especially since he hasn’t even begun formal lessons in any area yet.  

Any advice would be helpful!

–Leah