Alfalfa Looper Moth Caterpillar

After a fairly thorough search through Bug Guide, I believe your caterpillar here looks like one of the Looper Moths. Your caterpillar looks very much like Autographa californica, Alfalfa Looper Moth: http://www.wildutah.us/html/butterflies_moths/moths/h_m_autographa_californica_alfalfa_looper.html For reference, here is what a Luna Moth caterpillar looks like: http://bugguide.net/node/view/626014/bgimage

I believe that this is a different species than a Luna moth. The body of your caterpillar seems to be more slender and the markings are different. I will see if I can find a closer match for you.

Maybe a Luna moth caterpillar?? Not sure.

This looks like a moth caterpillar. Unfortunately, I am not sure I can give you much more info at this time. If you are feeling adventurous and have a bit of time, you can try searching on Bugguide.net for a match. For butterflies and moths you can choose just to look at caterpillars. You can do a search for "green caterpillar" as well but you will have a load of images to go through. It depends how old this caterpillar is and what species to be able to tell how long it will take. If you can find what it eats, you could try to raise it. Good luck!