It can have action, adventure, drama, sci-fi, mystery, and things of that nature. However, NO fantasy, magic, harem, ecchi, and crap like that.
If you haven't read them before read Bakuman and BECK a read...Skip Beat is on going as is Yureka. 1/2 prince is ongoing but it's 4-6 months in between issues. Reimei no Arcana is good. I could probably list a ton of manga, but I'm not sure how "None of that crap" that you don't want. For example, CHObits is good imo, but lots of people don't think so and it is decently "ecchi" but that's not the purpose.
- Shinobi No Kuni
I could recommend more for those genre's, but you also said no mature.
Someone else who reads terra-formars! :D