Had Jupiter continued to gain weight, it would have grown ever hotter and hotter, and ultimately self-sustaining, raging nuclear-fusing fires may have been ignited in its heart. This would have sent Jupiter down that long, shining stellar road to full-fledged stardom. Had this occurred, Jupiter and our Sun would have been binary stellar sisters, and we probably would not be here now to tell the story. Our planet, and its seven lovely sisters, as well as all of the moons and smaller objects dancing around our Star, would not have been able to form. However, Jupiter failed to reach stardom. After its brilliant, sparkling birth, it began to shrink. Today, Jupiter emits a mere.00001 as much radiation as our Sun, and its luminosity is only.0000001 that of our Star. Comets are really traveling relic icy planetesimals, the remnants of what was once a vast population of ancient objects that contributed to the construction of the quartet of giant, gaseous planets of the outer Solar System: Jupiter, Saturn, Uranus, and Neptune. Alternatively, the asteroids--that primarily inhabit the region between Mars and Jupiter termed the Main Asteroid Belt--are the leftover rocky and metallic planetesimals that bumped into one another and then merged together to form the four rocky and metallic inner planets: Mercury, Venus, Earth, and Mars. Planetesimals of both the rocky and icy kind blasted into one another in the cosmic "shooting gallery" that was our young Solar System. These colliding objects also merged together to create ever larger and larger bodies--from pebble size, to boulder size, to mountain size--and, finally, to planet size. Astronomers have known for years that the temperatures of the lunar near-side are higher than those on the far-side. This is because the abundances of the heat- producing elements uranium and thorium are greater on the near-side than on the far-side. In addition, these higher temperatures are a consequence of the fact that most of the volcanic eruptions occurred on the lunar near-side.