NASA Space Hats T-Shirts

Launched as GRAIL A and GRAIL B in September 2011, the probes were renamed Ebb and Flow by schoolchildren in Montana. The probes operated in almost circular orbit near the lunar poles at an altitude of approximately 34 miles, until their mission came to an end in December 2012. The distance between the twin probes altered a bit as they soared over areas of lesser and greater gravity that were caused by visible topological features on the Moon's surface, such as impact craters and mountains--as well as by masses that were secreted beneath the lunar surface. Until 2004, no spacecraft had visited Saturn for more than twenty years. Pioneer 11 took the very first close-up images of Saturn when it flew past in 1979. After that flyby, Voyager 1 had its rendezvous about a year later, and in August 1981 Voyager 2 had its brief, but glorious, encounter. Nearly a quarter of a century then passed before new high-resolution images of this beautiful, ringed planet were beamed back to Earth. Other than the sun, no other celestial body significantly affects the earth as the moon does. It is well know that the moon affects the rise and fall of the ocean tide. Such is the effect of the gravitational pull between the earth and the moon. Jupiter is easily the largest planet in our solar system. To put its size in context, Jupiter is more than 300 times the mass of Earth. Here is the interesting part; Jupiter has 63 moons that orbit it and yet it is not the planet in the Solar System with the most moons. That honor belongs to the ringed-planet Saturn, which has 66 moons identified so far. Pluto, the farthest flung among the nine planets, has been the subject of heated debate on whether it really qualifies to be considered a planet. Nowadays, it is classified as a dwarf planet. Its orbit around the Sun is somewhat heavily elliptical. In fact, there are instances where Pluto is actually closer to the Sun than Neptune, the planet that precedes it.