The Secret Martians by Jack Sharkey

My first awareness was the whine of the converters, audible everywhere in Marsport, if not by ear, then by the soles of one's feet. Their thundering dynamos plunged potent destructive rays against the Martian sands, leaving in their wake invisible fountains of nascent oxygen and shimmering puddles of orange-white molten iron. They went on day and night without ceasing, partly to keep the mining companies on Earth from losing their franchises with Tri-Planet, but primarily to keep the Marsport populace from tumbling down in the streets with cyanosed lips and glazing eyes, as the breathable atmosphere sloughed away over the hilltops.

So I knew that I was in Marsport, at least. But not much else. My hands, when I tried to move them, proved to be bound, and tightly, at that. My fingers felt swollen and numb when I tried to flex them. There was something, a hood, a sack, a cloth, over my head, fastened about my throat, impairing my breathing slightly and my vision altogether.