My first care, after making ready to quit the Astronaut as soon as the light around should render it safe to venture into scenes so much more utterly strange, unfamiliar, and unknown than the wildest of the yet unexplored deserts of the Earth, was to ascertain the character of the atmosphere which I was presently to breathe.

Did it contain the oxygen essential to Tellurian lungs?
Was it, if capable of respiration, dense enough to sustain life like mine?
I extracted the plug from the tubular aperture through which I had pumped in the extra quantity of air that the Astronaut contained; and substituted the sliding valve I had arranged for the purpose, with a small hole which, by adjustment to the tube, would give the means of regulating the air-passage at pleasure.

The difficulty of this simple work, and the tremendous outward pressure of the air, showed that the external atmosphere was very thin indeed.

This I had anticipated.

Gravity on the surface of Mars is less than half what it is on Earth; the total mass of the planet is as two to fifteen.