Mercury’s axis has the smallest tilt of any of the Solar System’s planets (about 1⁄30 degree). Its orbital eccentricity is the largest of all known planets in the Solar System;[b] at perihelion, Mercury’s distance from the Sun is only about two-thirds (or 66%) of its distance at aphelion. Mercury’s surface appears heavily cratered and is similar in appearance to the Moon’s, indicating that it has been geologically inactive for billions of years. Having almost no atmosphere to retain heat, it has surface temperatures that vary diurnally more than on any other planet in the Solar System, ranging from 100 K (−173 °C; −280 °F) at night to 700 K (427 °C; 800 °F) during the day across the equatorial regions. The polar regions are constantly below 180 K (−93 °C; −136 °F). The planet has no known natural satellites.
The original goal of Cassini-Huygens was to study Saturn and its large, misty, tortured, moon Titan. Titan, the second-largest moon in our Solar System, after Ganymede of Jupiter, is a world long-shrouded in mystery, hiding behind a thick orange veil, and slashed with hydrocarbon lakes and seas. However, there are other enticing moons known to circle the ringed planet. Saturn's mid-sized icy moons (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, and Phoebe) are enchanting worlds. Each one of these frozen little moons reveals an interesting and unique geology. So far, Saturn is known to sport 62 icy moons!
For all its romance inspiring awesomeness, the moon has another side to its personality. Werewolves, mood swings and even wild behavior are often blamed on the full moon. How many times have you heard the question acrimoniously asked, "is it a full moon tonight?"
At last, on July 1, 2004, the Cassini spacecraft fired off its breaking rocket, glided into orbit around Saturn, and started taking pictures that left scientists in awe. It wasn't as if they hadn't been prepared for such wonders. The weeks leading up to Cassini's arrival at Saturn had served to intensify their already heated anticipation. It seemed as if each approach-picture taken was more enticing than the one preceding it.