The first pictures of Neptune, taken by Voyager at a distance of more than 300 million kilometers away, showed a bluish disk that was nearly the twin of Uranus, the seventh planet. However, here was one important difference: there were indistinct whitish spots, which were certainly clouds. But just a few weeks later, the probe got much closer and the pictures sent back to the Earth provided amazing and beautiful details: now Neptune stands out as an enormous globe on the Pasadena screens and, unlike the peaceful Uranus, is a very dynamic and stormy world, surrounded by at least four rings consisting of very small dust particles. The brightest ring is between 53 000 and 63 000 kilometers from the center of the planet. Its atmosphere, consisting of a thick blanket of hydrogen and helium and traces of methane, is similar to that of the Earth: through Voyager's television cameras it appears as an enormous turquoise marble crossed by thin frayed veins, some of which are almost white, while others are a darker blue. But the most amazing feature is a black oval spot, as large as the Earth, located slightly above the equator: a gigantic cyclonic perturbation. "It is like the eye of a Cyclops", notes the Italian planetologist Marcello Fulchignoni. "And, on the other hand, according to mythology, wasn't Polyphemus the favorite son of Neptune?". The monstrous storm moves quickly over the face of the planet, driven by impetuous winds, and completes a full revolution in about 18 hours. Very similar to Jupiter's great red spot, it whirls around itself in a counterclockwise direction and generates a series of smaller black spots in its wake - a progeny of storms. A second cyclone, four times smaller than the great black spot, moves around the southern hemisphere of the planet in a little more than 16 hours. Due to the high rotation speed, the smallest spot catches up to and passes the larger one every five complete revolutions of the planet. Less striking than the spots but perhaps even more interesting are the lighter "puffs" which accompany them: these are short-lived cirrus clouds of frozen methane, which are found in the higher layers of the atmosphere. One of these formations, located between the two dark spots, is driven in the opposite direction by strong gusts at a high altitude: it is so fast that scientist have nicknamed it "Scooter". Where Neptune gets the energy for such turbulence (its winds blow at almost seven hundred kilometers per hour) is a real mystery. Considering the very low temperature of the planet, which Voyager found to be -218 degrees Celsius, and its distance from the Sun (for which Neptune only receives a millionth of the radiation that strikes the Earth), there must be some internal source of heat, as was already determined from Jupiter and Saturn. But, for all that astronomers know, Neptune has a much simpler structure than its two "bigger" brothers. Like Uranus, it has a central rocky mass, with a diameter of about 16 000 kilometers, enveloped by an enormous sphere of semi-frozen material, a type of "cloak" consisting of water and liquid methane, which increases the total diameter of the planet to 49 400 kilometers. According to some researchers, since it is subjected to enormous pressure and temperatures in the core of the planet, the methane might decompose into hydrogen and carbon, leading to the crystallization of the latter element. If this were true, Neptune's heat might be generated by the most expensive motor in the cosmos: an immense dynamo encrusted by a diamond and fed by the mutual motion of the fluid parts in the core of the planet. A mechanism that might also be responsible for the magnetic field detected by Voyager which, unlike the one on the Earth, which is more or less aligned along the axis of rotation, is tilted at an angle of 50 degrees.
The first pictures of Neptune, taken by Voyager at a distance of more than 300 million kilometers away, showed a bluish disk that was nearly the twin of Uranus, the seventh planet. However, here was one important difference: there were indistinct whitish spots, which were certainly clouds. But just a few weeks later, the probe got much closer and the pictures sent back to the Earth provided amazing and beautiful details: now Neptune stands out as an enormous globe on the Pasadena screens and, unlike the peaceful Uranus, is a very dynamic and stormy world, surrounded by at least four rings consisting of very small dust particles. The brightest ring is between 53 000 and 63 000 kilometers from the center of the planet. Its atmosphere, consisting of a thick blanket of hydrogen and helium and traces of methane, is similar to that of the Earth: through Voyager's television cameras it appears as an enormous turquoise marble crossed by thin frayed veins, some of which are almost white, while others are a darker blue. But the most amazing feature is a black oval spot, as large as the Earth, located slightly above the equator: a gigantic cyclonic perturbation. "It is like the eye of a Cyclops", notes the Italian planetologist Marcello Fulchignoni. "And, on the other hand, according to mythology, wasn't Polyphemus the favorite son of Neptune?". The monstrous storm moves quickly over the face of the planet, driven by impetuous winds, and completes a full revolution in about 18 hours. Very similar to Jupiter's great red spot, it whirls around itself in a counterclockwise direction and generates a series of smaller black spots in its wake - a progeny of storms. A second cyclone, four times smaller than the great black spot, moves around the southern hemisphere of the planet in a little more than 16 hours. Due to the high rotation speed, the smallest spot catches up to and passes the larger one every five complete revolutions of the planet. Less striking than the spots but perhaps even more interesting are the lighter "puffs" which accompany them: these are short-lived cirrus clouds of frozen methane, which are found in the higher layers of the atmosphere. One of these formations, located between the two dark spots, is driven in the opposite direction by strong gusts at a high altitude: it is so fast that scientist have nicknamed it "Scooter". Where Neptune gets the energy for such turbulence (its winds blow at almost seven hundred kilometers per hour) is a real mystery. Considering the very low temperature of the planet, which Voyager found to be -218 degrees Celsius, and its distance from the Sun (for which Neptune only receives a millionth of the radiation that strikes the Earth), there must be some internal source of heat, as was already determined from Jupiter and Saturn. But, for all that astronomers know, Neptune has a much simpler structure than its two "bigger" brothers. Like Uranus, it has a central rocky mass, with a diameter of about 16 000 kilometers, enveloped by an enormous sphere of semi-frozen material, a type of "cloak" consisting of water and liquid methane, which increases the total diameter of the planet to 49 400 kilometers. According to some researchers, since it is subjected to enormous pressure and temperatures in the core of the planet, the methane might decompose into hydrogen and carbon, leading to the crystallization of the latter element. If this were true, Neptune's heat might be generated by the most expensive motor in the cosmos: an immense dynamo encrusted by a diamond and fed by the mutual motion of the fluid parts in the core of the planet. A mechanism that might also be responsible for the magnetic field detected by Voyager which, unlike the one on the Earth, which is more or less aligned along the axis of rotation, is tilted at an angle of 50 degrees.
