Poll: Who on ____ could have done it?

ALNAQBI

^k^

Stewart

I feel either can be used. The emphasis of the statement is a common ground (how apt) between all of humanity. We all live on Earth, and to (I suppose) a lesser, yet still great, extent we all live on soil/ground/earth aswell.

paandu

we all know that EARTH is the only planet with living creatures....it is unique..nothing can replace it.In my perspective it should always be indicated with upper case letters...

Norasan

I like the AP style rule that Earth with a capital E is reserved for reference to the planet in the solar system. Earth with a lower-case e belongs in idioms, such as "Who on earth ...?" and "What on earth?"