Nepturne: Fast Facts and Images
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Planetary Parameters - find out how planetary parameters influence habitability Ratio
(Neptune/Earth)
Planet Type Gas Giant (unlike a solid, rocky planet like Earth)  
Average Distance from Sun (kilometer) 4,498,300,000 compared to Earth's 149,600,000 30.07
Equatorial Diameter (kilometer) 49,532 as compared to Earth's 12,756 3.88
Mass (1024 kilogram) 102.43 as compared to Earth's 5.9736 17.15
Volume (1010 kilometer3) 6,254 as compared to Earth's 108.321 57.74
Average Density (gram/centimeter3) 1.64 as compared to Earth's 5.52 0.30
Surface Gravity (meter/second2) 11.2 as compared to Earth's 9.78 1.13
Magnetic Field (gauss-Rh3) 0.142 as compared to Earth's 0.3076 0.46

Orbital Parameters - find out how orbital parameters influence habitability
Year Length (One Orbit Around the Sun) 164.79 Earth years
Day Length (One Rotation on its Axis) 16.11 Earth hours
Inclination of Axis (degrees) 29.56 compared to Earth's 23.45

Atmosphere and Climate - find out how atmospheric parameters influence habitability
Average Surface Temperature (C) -204 at one bar as compared to Earth's 14.8
Minimum Temperature (C) -215 at one bar as compared to Earth's -33
Atmospheric Pressure at Surface Greater than 100 bars (Earth = 1 bar) This pressure exerts a force of 0.45 kg/m3 at 1 bar compared to Earth's atmosphere which exerts a force of 1.217 kg/m3 at 1 bar (sea level).
Major Atmospheric Gasses 80.0 % Hydrogen, 19.0% Helium, 1.5% Methane
Summary of Water There is no liquid water or water vapor

Planetary Features - find out how planetary features influence habitability
General Overview Neptune is a gaseous ball with a banded blue atmosphere decorated with white clouds of methane ice. It has several large dark spots like Jupiter's Red Spot.
Known Moons/Rings Triton is 2,700 km in diameter. Also, there are two 300-400 km moons, two 150-200 km moons, and three 50-100 km moons. Neptune's four rings and several diffuse sheets of particles are made of dark materials, are discontinuous, and are thicker in certain sections.

Visits to Neptune - find out how visits to a planet are significant to figuring out it's habitability
1950-present 1989: Voyager 2 (US), flyby, discovers six small moons.

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Captioned Images of Neptune
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image 1 of Neptune     image 2 of Neptune

1-2) Neptune's clouds show more variety and contrast than Uranus's. Even though it is farther from the sun, Neptune is slightly warmer than Uranus. This warmth, thought to be from the compression of gasses when Neptune formed, creates layers in the atmosphere. This layering creates banding and white frozen methane clouds. The warmth also generates winds up to 2,000 km per hour. Oddly, these winds blow in the opposite direction to Neptune's rotation. Astronomers theorize that Neptune may have "slushy" interiors containing thick layers of water clouds.

image 3 of Neptune   image 4 of Neptune   image 5 of Neptune

3-5) Neptune has several storm systems similar to Jupiter's. The largest, called the Great Dark Spot, is the size of Earth. The storm stays in the same general spot, presumably over a plume of rising warm gas. The disruption and turbulence it causes to the cloud bands encountering it make the storm visible (see the center set of sequenced images above).

image 6 of Neptune   image 7 of Neptune   image 8 of Neptune

6-8) Neptune has eight moons. Triton (center, above), is the largest. Neptune's four rings are not even -- they are thicker in some places and so thin in others that there are openings, making for discontinuous rings. On the right, the brightly reflecting Neptune has been masked so that the camera could image the faint rings.