| MadSci Network: Astronomy |
What causes the high wind speeds on Neptune?
This is a very good question. On the Earth, winds are caused by the Sun. Radiation from the Sun heats the surface of the Earth unevenly. This causes the atmosphere to convect in order to attempt to even out the heat distribution, resulting in winds. Wind patterns are affected by changes in solar heating with latitude, the Coriolis effect (see below), the configuration of continents and oceans, and the location of mountain ranges.
As mentioned, Neptune receives only 1/900th of the amount of solar energy as the Earth does. As a consequence, another heat source must be present to cause wind gusts of such high velocity (up to 900 miles per hour). This source is the internal heat of the planet.
The Earth absorbs more heat coming in from the Sun than it produces from the decay of radioactive elements in its interior. However, the opposite is true for the Jovian planets (Jupiter, Saturn, Uranus, and Neptune). The internal heat is caused by the gravitational contraction that formed the planets billions of years ago (potential energy was converted into kinetic energy as material accumulated to form the planets, which is now being released as heat). This internal energy source is the main source of heat for the atmosphere of Neptune, though the Sun still contributes as a heat source.
References:
Seasons on Neptune
The Coriolis force
Hamblin, W.K. and E.H. Christiansen. Earth’s Dynamic Systems. Upper Saddle River, NJ: Prentice Hall, pp. 438-459, 2001.
Hartmann, W.K. Moons and Planets. Belmont, CA: Wadsworth Publishing Company, pp. 191-235, 1999.
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