Couple Of Things About This:
- Moons Count.
- It Doesn't Have To Be A Thriving Civilization, Just Landing On The Planet Counts.
- Starting Planet Doesn't Count.
If You Want It As Fast As Possible In One Playthrough:
- Go To The Moon, Terraform It.
- Go To Rock Planet, Grab Planet Cracker Piece, Build Observatory.
- Go To Ice Planet, Terraform It, Grab Cracker Piece.
- Go To Lava Planet, Terraform It.
After You've Done The Above, You Can Use An Observatory On Your First Planet And On Rock World To See A Total Of 10 Planets.
- This Is Excluding Your First, And Including The Ones You've Already Visited
Save Your Game.
- Send 5 Nuggets And 40 Food To The Rest Of The Observable Planets, Even If They Die Before You Send The Rest Of The Rockets, It Will Count As Long As You Done Mark Any As Failures.
Afterwards Reload To The Previous Saved Game So You Dont Have 6 Failing Colonies. (You Can Also Go For Endings From This Point Too)
Achievement Unlocks As 10 Total Planets Are Visited (Again, After The First Planet, And Including The Moons)
Good Luck!