I asked for a moderator to move this to the relevant Destination forum as this is not relevant for BA or BAEC.
The answering posts will be moved there too so:
- I would give a pass on NASA for such a short layover: it is quite south of Downtown so you are looking at easily 60 minutes drive just to go there, and that is assuming low traffic. Moreover the NASA is not that interesting unfortunately and dumb-ed down. If you are a space exploration buff, you will be disappointed I am afraid.
- You have enough times to go for a late lunch in Rice Village followed by a quick visit to the Museum of fine arts. However the traffic back to IAH at around 18:00 will be heavy.