That's Mars. And over there, that is Venus. What a treat - two planets in the same sky.

Men Are From Mars, Women Are From Venus.

Planets that don't currently sport plate tectonics, such as Venus and Mars, are scarcely habitable. Tectonics might be a requirement of any world that aspires to a rich diversity of life.

But whence came this curious difference between them? He found that he could point to no single feature wherein the difference resided, yet it was impossible to ignore. One could try - Ransom has tried a hundred times - to put it into words. He has said that Malacandra was like rhythm and Perelandra like melody. He has said that Malacandra affected him like a quantitative, Perelandra like an accentual, metre. He thinks that the first held in his hand something like a spear, but the hands of the other were open, with the palms towards him. But I don't know that any of these attempts has helped me much. At all events what Ransom saw at that moment was the real meaning of gender.

The two creatures were sexless. But he of Malacandra was masculine (not male); she of Perelandra was feminine (not female). Malacandra seemed to him to have the look of one standing armed, at the ramparts of his own remote archaic world, in ceaseless vigilance, his eyes ever roaming the earth-ward horizon whence his danger came long ago. "A sailor's look," Ransom once said to me; "you know... eyes that are impregnated with distance." But the eyes of Perelandra opened, as it were, inward, as if they were the curtained gateway to a world of waves and murmurings and wandering airs, of life that rocked in winds and splashed on mossy stones and descended as the dew and arose sunward in thin-spun delicacy of mist. On Mars the very forests are of stone; in Venus the lands swim. For now he thought of them no more as Malacandra and Perelandra. He called them by their Tellurian names. With deep wonder he thought to himself, "My eyes have seen Mars and Venus. I have seen Ares and Aphrodite.

There's room for another planet between Mars and Jupiter. Given that planets formed everywhere else, why couldn't another planet have formed there?