But I have also observed a curious phenomenon. The orbits of the major Jovian moons are endlessly complex, and there are times when only one moon is aloft in the skies of Thanator during the day. This, oddly enough, in no way diminishes the amount of daylight. The quantity of the daylight remains constant no matter how many moons are aloft, and whether or not the giant orb of Jupiter is visible. I have often wondered if what seems to be daylight is not some radiant effect of the upper atmosphere; I have mentioned earlier in this account of my adventures the odd appearance of the skies of Thanator―that appearance of a crawling film of golden mists. Perhaps the illumination of the moon's surface is somehow due to the effects of radiation striking that golden mist, which must be a layer of unknown gas high above the breathable air of Thanator. An effect perhaps akin to the light that flares from inert neon gas when an electrical current passes through it. You will of course be familiar with neon signs, that boon to the advertising profession: the inert vapor lies in glass tubes, which, when an electrical current is passed through them, blaze with light. Perhaps the upper layers of the atmosphere of Thanator are composed of neon, or of some comparable gas which, during the hours of daylight, is under the bombardment of electrical forces.
But this was only one of the baffling questions that had puzzled me during the many weeks of my captivity.
I had given considerable thought to the problem of just where I was. Astronomy has always interested me, and as I have a good head for figures and an almost photographic memory, I was able to recall quite a bit of information about the solar system, enough, it seemed, to base a firm opinion.
This, obviously, was one of the twelve moons of Jupiter. It could hardly be either of the two planets nearest to Jupiter, which are Mars and Saturn. Mars is something like three hundred million miles closer to the sun than Jupiter, and surely even that banded and Brobdingnagian giant would not bulk so hugely in its skies. Besides, Mars has only two moons and this world at least four.
Nor could it very easily be Saturn, and for much the same reasons. For Saturn was even farther away from Jupiter than was Mars―somewhere in the neighborhood of four hundred million miles distant.
The only bodies close enough to Jupiter for the giant world to bulk so enormously in their skies would be the Jovian satellites themselves. I recalled that some of these are quite large―lo, the second moon counting outwards from Jupiter, is about two thousand miles in diameter, only slightly smaller than Earth's own moon. Europa, the next of the satellites, is slightly smaller than that, while the fourth moon, Ganymede, with its diameter of more than three thousand miles, is perhaps the largest of all the moons in the solar system. The fifth moon, Callisto, has a diameter of about two thousand seven hundred miles. The moons beyond the orbit of Callisto, Hestia, Hera, Demeter, are all extremely small, with a diameter of eighty to ten miles each. These three I could safely eliminate from consideration. And the four outermost of the Jovian moons―Adrastea, Pan, Poseidon, and Hades―could also safely be eliminated because of their very small size, as well as their retrograde orbits. My conclusion, then, was easy and obvious. Three large moons and one very small one were visible in the night sky between this world of Thanator and its titanic primary; they must be the four innermost of the Jovian satellites, the first moon, Amalthea, and the three larger ones, lo, Europa, and Ganymede. Hence I decided, to my own satisfaction, at least, that Thanator was Callisto!
But if this is true, how can the gravity of Callisto be so very similar to that of Earth? Earth's diameter at the equator is 7,927 miles, almost three times larger than Callisto. It would seem natural for Callisto to have a gravity one third that of Earth, but such is not the case.
And how can a world so small hold an atmosphere? Earth's moon is only a little smaller than Callisto, and its gravity is insufficient to hold anything like this thick rich air that I had been breathing now for two months. Would I ever find the answer to these mysteries?
During the entire period of my stay on Thanator, I have never ceased to puzzle over the curious and baffling anomalies between what I knew the surface of a Jovian satellite should be like, and the living reality through which I moved.
Everything that the terrene astronomers had ever discovered about the conditions on other worlds made it clear that Callisto should be a dead, frozen, airless world of jagged peaks and ammonia snow. Yet I walked through a jungle landscape of weird, terrific grandeur, limned in vivid and unlikely hues, and teeming with exotic life.
To this day I have not discovered the answer to this riddle.
On the third day of my freedom, I was suddenly arrested by the sounds of a battle some distance ahead of me.
I had been remarkably fortunate in that my journey through the black and crimson jungles had thus far brought me into no dangerous encounter with any of the ferocious predators wherewith this planet swarmed. In part this was due, I suppose, to blind chance or luck; but to some degree it was the result of a certain oily cream prepared by the arthropods. This substance, the distillation of an herbal sap, had the peculiar property of protecting the traveler who smeared himself therewith from the attack of a yathrib. For, although odorless to my nostrils at least, the substance is extremely offensive to the yathrib.
The Yathoon hunters use it to drive the yathrib from their proximity while engaged in rounding up a beast called the vastodon, which they hunt for its succulent meat. The yathrib is a predator who does not scruple to attack even a Yathoon hunter, and when one of the tribal hunts are in session the fearsome dragon-cat of the Thanatorian jungle has the annoying habit of lying low while the hunters round up their meat-beasts, and then charging in to carry off a prize for itself. The offensive cream, therefore, is a valuable adjunct to these meat-gathering expeditions, and I had taken the precaution to carry off a jar and kept my bare arms and legs liberally smeared with the oily stuff.
I burst through a wall of foliage into a small glade or clearing, and an astounding tableau met my eyes.
At one end of the clearing a snarling, hulking brute crouched, about to charge.
Facing him, her back against a tree trunk, her hands empty of any weapon, a young and beautiful woman faced the predator . . . and at last I knew for certain that the jungle moon of Thanator was inhabited by humans like me!
6. DARLOONA, WARRIOR PRINCESS OF THE KU THAD
I had long suspected that the insect creatures of the Yathoon Horde were not the only intelligent inhabitants of Thanator. The fact that Koja and his kind found me remarkable for my coloring rather than my physical being indicated that they were not unfamiliar with races akin to mine. And that slighting remark the jealous Gamchan had let fall, when he suggested I was some sort of a hybrid born of a mating between "the Zanadar pirates" and "the Ku Thad," reinforced my suspicion. And then the fact of that writing case I had found among Koja's possessions: a race ignorant of letters does not bother to invent writing cases.
Now, as I stared across the clearing at the first human being I had seen on Thanator, I found my pulse quickening, as much from the beauty of the young woman as from the surprise of the encounter.
She was perhaps twenty, tall and slender and superbly feminine. She wore a high-necked, open-throated leather tunic identical with the one Koja had given me, a tunic which extended down over her rounded hips, leaving her long and graceful legs bare save for soft buskins laced high on the instep. A wide girdle heavy with ornaments of precious metals cinched in her small waist, and from this depended a small pouch, an empty dagger scabbard, and a large medallion of some bright metal I could not at once identify.