Sphinx's reality alter powers and immortality would allow him to roll right over meltdown. Not to mention eons of experience and knowledged. Plus he's used to working in non-earth environments. It is possible that Meltdown could be come dissoriented or simply startled by the strange Blue Area. Sphinx is also ruthless, doing anything to get what he wants. he might simply toss Meltdown into the airless part of the moon.