Triton

The moon does not have to form with the planet. It can be captured into the Orbit! This is exactly what happened with Triton. The object which was most likely a dwarf planet from the Kuiper belt became a moon of Neptune!

Triton’s Place around Neptune

Neptune has 14 known moons in its orbit; Triton is the largest of them having about 99.5% of the mass of total satellites orbiting. The first 7 moons are regular moons having almost circular orbits in the same plane. Triton is the 8th moon having an irregular orbit. It is inclined to the planar orbit by 130 degrees. Triton is set apart from other moons in our solar system by the fact that it orbits its parent planet in the opposite direction of its direction of rotation. And this is because the moon has been captured into the orbit! It is believed that it was a part of a binary system (a celestial body was orbiting Triton when Neptune came closer). And due to the effect of its gravity, the celestial body was launched out of its orbit, providing enough momentum to Triton to stay in Neptune’s orbit.

Diameter	2700 km
Mass	2.1 x 1022 kg
Density	2.059 g/cm3
Surface Gravity	0.779 m/s2
Average Orbit Distance	354,759 km
Mean orbit Velocity	15,803.2 km/h
Escape Velocity	5,229 km/h

Triton-Pluto Similarities

Triton is slightly larger in diameter than Pluto by around 330 km. The studies from Voyager 2 visit of Triton in 1989 and New Horizon’s visit to Pluto in 2015 suggest that these two bodies share a lot of similarities. Both Have a Large amount of Nitrogen Ice on the surface with a mixture of other ice such as water and carbon dioxide. Red patches can be seen on Pluto and Triton, which is believed to be a result of a reaction between Sun's UV light and methane that creates an organic compound named ‘Tholin’. And that’s why they are thought to be originated from the same place in our solar system: ‘Kuiper Belt’.

Triton’s Surface

Even though it has organic compounds on its surface it is highly unlikely for life(that we know of) to evolve as the surface temperature drops down to -235 degrees celsius. The surface of Triton looks fairly young as there are hardly any craters. The water volcanos constantly spit out liquid water from below the surface, which freezes and settles down to form large flat regions. Voyager 2 managed to see a constant surface topography consisting of ice plains, ridges and plateaus.

Cryovolcanism on Triton

Deep Under Triton’s Crust is Rocky and metallic Core. Resulting in fairly high density for a moon. The materials inside the core are likely to undergo radioactive decay generating a lot of heat. This heats the moon from inside melting the lower portions of the crust and forming a subsurface ocean. Similar to Titan (Moon of Saturn). The dark organic materials like tholin under the ice absorbs heat from the light rays and creates pockets of water under the surface. This volume of water errupts from the thin icy regions and deposits the reddish dark minerals onto the surface. 

Fun Facts

• Triton has an Atmosphere. But it is As thin as 80 km above the Earth’s Surface. 

• Triton has more mass than the combined mass of all the other smaller moons in the solar system. 

• Triton’s surface reflects 70 percent of sunlight due to condensed nitrogen on the surface.