The atmosphere of Uranus is composed of 83% hydrogen, 15% helium, 2% methane and small amounts of acetylene and other hydrocarbons. Methane in the upper atmosphere absorbs red light, giving Uranus its blue-green color. The atmosphere is arranged into clouds running at constant latitudes, similar to the orientation of the more vivid latitudinal bands seen on Jupiter and Saturn. Winds at mid-latitudes on Uranus blow in the direction of the planet's rotation. These winds blow at velocities of 40 to 160 meters per second (90 to 360 miles per hour). Radio science experiments found winds of about 100 meters per second blowing in the opposite direction at the equator.
Uranus is distinguished by the fact that it is tipped on its side. Its unusual position is thought to be the result of a collision with a planet-sized body early in the solar system's history. Voyager 2 found that one of the most striking influences of this sideways position is its effect on the tail of the magnetic field, which is itself tilted 60 degrees from the planet's axis of rotation. The magnetotail was shown to be twisted by the planet's rotation into a long corkscrew shape behind the planet. The magnetic field source is unknown; the electrically conductive, super-pressurized ocean of water and ammonia once thought to lie between the core and the atmosphere now appears to be nonexistent. The magnetic fields of Earth and other planets are believed to arise from electrical currents produced in their molten cores.
Uranus Statistics Discovered by William Herschel Date of discovery 1781 Mass (kg) 8.686e+25 Mass (Earth = 1) 1.4535e+01 Equatorial radius (km) 25,559 Equatorial radius (Earth = 1) 4.0074 Mean density (gm/cm^3) 1.29 Mean distance from the Sun (km) 2,870,990,000 Mean distance from the Sun (Earth = 1) 19.1914 Rotational period (hours) -17.9 Orbital period (years) 84.01 Mean orbital velocity (km/sec) 6.81 Orbital eccentricity 0.0461 Tilt of axis (degrees) 97.86 Orbital inclination (degrees) 0.774 Equatorial surface gravity (m/sec^2) 7.77 Equatorial escape velocity (km/sec) 21.30 Visual geometric albedo 0.51 Magnitude (Vo) 5.52 Mean cloud temperature -193°C Atmospheric pressure (bars) 1.2 Atmospheric composition