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Jupiter's Atmosphere

Jupiter's great red spot
Jupiter's Great Red Spot (Click on the image for a larger view)
  • Atmospheric features of broadly different sizes appear to move with uniform velocities. That suggests that mass motion (movement of material) and not wave motion (movement of energy through a relatively stationary mass) was being observed.

  • Rapid brightening of features in the atmosphere was followed by spreading of cloud material. That is probably the result of disturbances that trigger convective (upwelling and downwelling) activity.

  • A pattern of east-to-west winds extends as far poleward as 60 degrees north and south, roughly similar to the pattern seen in more temperate areas where belts and zones are visible. Previous investigations led scientists to believe the near-polar regions (above 45 degrees latitude) are dominated by convective upwelling and downwelling. Voyager showed they apparently are not, at least up to 60 degrees latitude, and probably to 75.

  • Material associated with the Great Red Spot, Jupiter's most prominent atmospheric feature, moves in a counter-clockwise (anticyclonic) direction. At the outer edge, material appears to rotate in four to six days; near the center, motions are small and nearly random in direction.

  • Small spots appear to interact with the Great Red Spot and with each other.

  • Voyager instruments observed auroral emissions, similar to Earth's northern lights, in the polar regions, in ultraviolet and visible light. Pioneer 10 and 11 didn't see the ultraviolet emissions during their encounters. The auroral emissions appear to be related to material from Io that spirals along magnetic field lines to fall into Jupiter's atmosphere.

  • Voyager also saw cloud-top lightning bolts, similar to superbolts in Earth's high atmosphere.

  • Atmospheric temperature at 5 to 10 millibars (1/200th to 1/100th Earth's surface atmospheric pressure) is about 160 Kelvins (-170 degrees Fahrenheit). An inversion layer -- a warmregion above a cold layer, similar to the phenomenon that traps smog in the Los Angeles Basin -- exists near the 150-millibar level. (Pressure at Earth's surface is about 1,000 millibars.)

  • The Voyagers observed ionospheric temperatures that changed with altitude, reaching about 1,100 Kelvins (1,500 degrees Fahrenheit). That was also not observed by Pioneers 10 and 11, and Voyager scientists believe they are witnessing large temporal or spatial changes in the ionosphere of Jupiter.

  • The Voyagers measured helium in the upper atmosphere; its percentage compared to hydrogen is important to understand composition and history of the atmosphere -- and the primordial cloud of which the Sun and planets formed. Relative abundance of helium to hydrogen is about 11 percent by volume.

 

 
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