Great control of the composition none the less. However there is one thing:
purple crotch....or "John Carter: Feel the wrath of my tea bag, Villain!"
Jokes aside, I love how action oriented this is. the Dynamism of John is great as he is poised to enact some epic "foot to ass" on the Martian and how his buddy, who is being blocked by John Carter is dumbfounded and afraid all at the same time.
That's hilarious that they have included Gullivar Jones into the John Carter world, since Gullivar actually came before Carter. It is a logical melding and should make for an interesting story! Great job on the cover, Joe!
"Under the Moons of Mars", Edgar Rice Burrough's first published work, was serialized in All-Story Magazine in 1912. He submitted it with the pen name "Normal Bean" as a sign that the fantastical happenings in the story were not the ravings of a lunatic, but the imaginings of a man with a normal "bean" (head, or brain). But the editors decided that "Normal" was a typo, so the story was published under the name "Norman Bean". When the story was published as a novel with the title A Princess of Mars, Burroughs decided to have it published under his own name.