The green hue was a puzzle for astronomers in the early part of the 20th century because none of the known spectral lines at that time could explain it. There was some speculation that the lines were caused by a new element, and the name nebulium was coined for this mysterious material. With better understanding of atomic physics, however, it was later determined that the green spectrum was caused by a low-probability electron transition in doubly ionized oxygen, a so-called “forbidden transition”. This radiation was all but impossible to reproduce in the laboratory at the time, because it depended on the quiescent and nearly collision-free environment found in the high vacuum of deep space.
Unfortunately, the various economic troubles which are plaguing Europe has caused ESA to spend less money than before, so many space programs in Europe has halted. However, both in China as well as in India, there are several ambitious programs present, which may cause any one of these nations to send another man to the moon in the next decade. Naturally, only time will tell; but nothing will change the fact that mankind's future is in the stars.
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.
A Distant, Dusty Moon. Titan experiences changing seasons--just like Earth. In particular, Titan's seasons change around the equinox, when our Sun passes Titan's equator. At this time, huge clouds can form in tropical areas, resulting in violent methane storms. Cassini observed these ferocious methane storms during several of its flybys over Titan.