Neptune: Atmosphere and Magnetosphere

The Atmosphere

Neptune’s atmosphere is mostly hydrogen and helium with a small amount of methane. Atmospheric composition is believed to be 80 percent molecular hydrogen, 19 percent helium, and 1.5 percent methane. Trace amounts of hydrogen deuteride and ethane exist, as well as aerosols ammonia ice, water ice, ammonia hydrosulfide, and possibly methane ice. Neptune owes its blue color to the atmosphere: the methane present absorbs red light.

The Magnetosphere

Neptune’s magnetosphere is medium sized, but still much larger than Earth’s. It is generated in the middle region, unlike a terrestrial planet’s magnetosphere, which generates in the metal core. Unlike Saturn or Jupiter, however, Neptune does not have a layer of metallic hydrogen zones—there is not enough pressure to form one. The magnetic field is probably generated by the movement of water or some other conducive material in the icy mid region of the planet. As a result, Neptune’s magnetic field is oddly oriented, at an extreme 60-degree tilt. This magnetosphere, like Saturn’s, produces radio emissions and other waves.

Copyright © 2000 by Gary Chan and Matthew McDermott. All rights reserved.