Triton (moon)

William Lassell

Triton ( Neptune I) with a diameter of 2707 kilometers by far the largest moon of the planet Neptune, and the seventh largest moon and the sixteenth largest body in the solar system.

• 3.1 atmosphere
• 3.2 Surface
• 3.3 seasons
• 3.4 Internal structure

Discovery and designation

Triton was discovered on October 10, 1846 by brewer and amateur astronomer William Lassell. Only 17 days before Johann Gottfried Galle discovered the giant planet Neptune. As learned John Herschel of the discovery of Neptune, he wrote a letter Lassell, in which he proposed him to look for possible moons out. Lassell did so and found Triton after eight days.

It was named after the moon Triton, a sea god of Greek mythology, often referred to as the son of Poseidon. The name was first proposed in 1880 by Camille Flammarion and other astronomers, but the name was not officially used for a long time. For records from 1939 show that although the moon had a name but it was not in general use. In the astronomical literature was only the moon of Neptune 's speech. It seems a little strange that Lassell himself forgave no name, only a few years before his discoveries, the eighth Saturn 's moon Hyperion and the Uranian satellites Ariel and Umbriel were yet been officially named.

Web properties

Orbit

Triton orbits Neptune in a retrograde, almost perfectly circular orbit at an average distance of 354,759 km (about 14.326 Neptune radii ) from its center, ie 330,000 km on whose cloud tops. The orbital eccentricity is 0.000016, the web is highly inclined with 156.885 ° relative to the equator of Neptune.

The orbit of the next inner moon Proteus is 237.1 thousand km away from Triton's orbit, that of the next outer moon Nereid on average 5.159 million km, due to the high orbital eccentricity comes Nereid Triton up to about one million kilometers near.

Triton orbits Neptune in 5 days, 21 hours, 2 minutes and 40.2 seconds. He runs around the planet retrograde ( decreasing) unlike most moons of the solar system, that is contrary to the direction of rotation, which is highly exceptional and unique in the solar system for a moon of this size and relatively small distance to the central body.

Triton orbits Neptune within a critical distance, so it is exposed to very strong tidal forces of the gas planets. Since Triton Neptune continues to approach him, he is going to happen, according to calculations in 100 million years, the Roche limit inward and be torn apart, its components will form a larger ring system similar to that of Saturn.

Probably Triton is a larger object of the Kuiper belt, which was captured by Neptune by its gravitational effect. He could the dwarf planet Pluto and its moon Charon be very similar to the structure as well as other members of the Kuiper belt.

Rotation

The rotation period is equal to the orbital period and Triton has with how the Earth's moon, a synchronous rotation, which thus in the same downward direction of rotation takes place also within 5 days, 21 hours, 2 minutes and 40.2 seconds. Its rotation axis is exactly perpendicular to its orbital plane.

Physical Properties

Triton has a mean diameter of 2706.8 km, making it by far the largest moon of Neptune. Triton alone possesses 99.5 % of the total mass surrounding the Neptune, it therefore falls 0.5 % to the other 13 moons and Neptune's ring system. He also has more mass than all the moons in the solar system, which are smaller than Triton, taken together.

Triton's mean density is 2.05 g/cm3. It has a high albedo of 0.76, that is, 76 % of the incident solar light is reflected. This is because a large part of its surface is covered with ice.

The lowest measured temperature at the surface is 35.6 K or -237.6 ° C, the deepest ever directly measured by a probe in the solar system.

The total area is about 23.018 million square kilometers and is thus roughly the area of North America ( excluding Greenland ).

Atmosphere

The surface temperature of Triton is deep enough resources to hold the atmosphere despite the low gravity, which is 99 % nitrogen, 1 % methane and trace amounts of carbon monoxide. However, the pressure of 1.4 - which corresponds approximately to the atmospheric pressure 1/70.000 on earth 1.9 Pascal, is extremely low. However, caused by sunlight convection care in the thin atmosphere that promoted by Triton's geysers on the surface material is distributed over large areas.

Surface

As Voyager 2 on August 25, 1989 flew by Neptune and its moons, she sent this fascinating images of Triton's surface. There was a network of dislocations, where the icy crust has been deformed and broken, with only a few impact craters are present. This suggests that the moon is geologically active, with the traces of older craters were obliterated by geological or atmospheric processes. Large impact basins appear to have been filled several times by viscous material from the interior.

What was surprising was the evidence of a kind of "cold" volcanism, which is called Kryovulkanismus ( refrigeration or ice volcanism ). It active geysers were found to emit a mixture of liquid nitrogen and entrained rock dust up at 8 km altitude. These are visible on the Voyager recordings as dark plumes of smoke. The reason for this is probably the seasonal heating by solar radiation be sufficient despite their low intensity to vaporize frozen nitrogen. The ejected particles are deposited on the surface and form deposits of frozen methane and silicates. Methane converted as a result of sunlight into other organic compounds to which are visible as dark streaks and stripes.

Well similar to Pluto is covered with dry ice Tritons surface to 55 % with frozen nitrogen to 15-35 % with water ice and to 10-20 %. In addition, a 0.1 % methane and 0.05 % Kohlenmonoxideis - share could be determined. Triton's surface covers 23 million square kilometers, which is roughly the size of North America excluding Greenland.

Seasons

Triton's axis of rotation is 157 ° from the axis of rotation of Neptune is inclined, which is relative to its orbit around the sun, in turn inclined 30 °. As a result, Triton poles are temporarily directly facing the sun, similar to those of the planet Uranus. While Neptune 166 years permanent orbit around the sun, there is between the times in which he turns the sun 's equatorial region, even more than 40 years at the North Pole and South Pole once a summer, during winter there on the opposite side. The associated temperature differences lead to strong seasonal effects.

At the time of the flyby of the Voyager 2 spacecraft, the south pole of the sun was facing in 1989, while the North Pole region was for about 30 years in the shadows, where temperatures up to -235 ° C ( 38 K) prevail. There, deposits of frozen nitrogen and methane were identified that appear to be heated again and again, alternating with the seasons, vaporize and condense as ice at each pole lying in the shade.

Internal construction

It is believed that Triton from a differentiated structure, a core of silicate rock and a crust of water ice. Research results from 2012 also point to the possibility that a thinner, ammonia-rich ocean exists beneath the surface. The energy to keep the ocean under the surface at -90 ° C liquid comes from the decay of radioactive substances in Triton's interior and the tidal friction that occurs when orbit around Neptune.

Research

Before the Neptune flyby of the Voyager 2 spacecraft in the summer of 1989, we knew of Triton is very little, although he has been known for 143 years. He was previously observed by ground-based telescopes only while its orbital elements and its brightness can be determined. Estimates of its size based on the presumed retroreflectivity and varied 3200-6000 km, because it was assumed that Triton was darker. Voyager 2 resulted in a swing-by of Neptune in 4824 km distance through to pass Triton on August 25, 1989, 39,790 km minimum distance. The geysers were discovered in subsequent evaluations of the images on 2 October 1989.

Since the flyby of the Neptune system ground-based observations as well as the Hubble Space Telescope has been studied intensively.

Frozen crater lakes with an impact crater

A cloud in the atmosphere