Colonization of the outer Solar System the Solar System's gas giant planets for exploration and possibly mining of helium-3, which could have a very high value per unit mass as a thermonuclear fuel. The Jovian system in general has particular disadvantages for colonization, including its severe radiation environment and its particularly deep gravity well. Its radiation would deliver about 3,600 rems per day to unshielded colonists on Io and about 540 rems per day to unshielded colonists on Europa. Exposure to about 75 rems over a few days is enough to cause radiation poisoning, and about 500 rems over a few days is fatal. Jupiter itself,
Mongo (fictional planet) peoples of Mongo have evolved into different forms, such as the winged Hawkmen, the tailed Lion Men, and the underwater dwelling Coralians. Mongo is about half the diameter of Earth but is considerably denser, so its gravity is only slightly weaker than the Earth's, though it still allows Flash Gordon to put his gymnastics skills to good use. Mongo has a variety of climates, and is inhabited by enormous, dinosaur-like monsters. In Alex Raymond's comic strip and the Flash Gordon movie serials, Mongo was shown as a rogue planet that had drifted into Earth's solar system. Later versions of the