Nice image, but that isn't a sphere, it is a circle face on a cylinder...sorry it is the mathematician in me.
The colours are a bit too saturated for my liking. I like the proportion of sky and grass though. Shame about the building on the left of the image.
Unfortunately, a cylinder isn't a sphere. Good attempt thought, as you used the rule of thirds well. One suggestion for overall improvement it to watch the background. The buildings are very distracting, and it feels like if you moved a bit to the left you wouldn't see them in the photo.
I'm sorry, I have two issues with this image. The first, it seems quite oversaturated on my screen. Second, this is a cylinder, not a sphere. (not voting right now.)