Barsoom is populated with many fantastic races and creatures, but the green man is perhaps the strangest of all. John Carter, on his advent to Mars, meets first the green men of the dead sea bottoms. Burroughs wrote that these creatures were fierce and unloving nomads and provides a description of their physical appearance. At birth the young appear to be all head and six limbs, two for walking erect, two used as arms and two in between which can be used as either. Eyes are set at extreme sides of heads and above center and can look in one or two directions without turning the head.
Noses are longitudinal slits entered in face midway between mouth and ears.
Light-greenish color in infants and women, deepening to dark olive for adult males. Iris of eye is blood-red, pupils are dark, eyeball is very white, as are the pair of tusks extending from the lower jaw upwards in a curve toward the center of the face where human eyes would be. Weight and mass would be different on Mars where the lesser gravity and less dense atmosphere, which is maintained by a fortified atmosphere manufacturing plant, would be major factors in growth and density of bone and tissue. Among the arguments presented are those that question the flexibility of a spine that would allow the green man to travel on all fours with the upper torso erect, similar to a centaur. Pre-supposing green Martians have bones as rigid and dense as terrestrial humans such an arrangement would indicate the need for a spine with a hinge or flex joint.