In the film Thor, Odin casts a spell on Mjolnir and strips Thor of his power. He then banishes Thor to Midgard (Earth). On Earth, Thor is seemingly just a strong and durable human. Later in the film, he becomes worthy, and regains control of Mjolnir. This then grants him his full power set and control over Mjolnir.
My question is, prior to this, could Thor control lightning all on his own? Or is this purely an ability of Mjolnir?