During my time in high altitude astronomy, I routinely witnessed workers breathing medical oxygen, industrial carbon dioxide, nitrogen and helium gas as part of their daily work routine.

Do as gas balloons do, while in depression; inhale helium of happiness and fly high.

Lives there upon any world such another as John Carter, Prince of Helium? Lives there another man who could fight his way back and forth across a warlike planet, facing savage beasts and hordes of savage men, for the love of a woman?

When I worked at the W. M. Keck Observatory on the 13,796 feet very high altitude summit of Mauna Kea, we would routinely be engulfed in cold clouds of helium and nitrogen gas as we discharged it into the video camera systems daily. The management team never warned us that we were in a hazardous oxygen deprived environment during this activity that was known for its ability to adversely affect physical and mental health, and possibly bring on death by asphyxiation.