| ELEMENTS DETECTED IN THE JOVIAN MAGNETOSPHERE | ||
|---|---|---|
| Element | Atomic Number | Instruments |
| Hydrogen (H) | 1 | UVS, Plasma, LECP, CRS |
| Helium (He) | 2 | Plasma, LECP |
| Carbon (C) | 6 | LECP |
| Nitrogen (N) | 7 | CRS |
| Oxygen (O) | 8 | UVS, Plasma, LECP, CRS |
| Neon (Ne) | 10 | CRS |
| Sodium (Na) | 11 | LECP, CRS |
| Magnesium (Mg) | 12 | CRS |
| Silicon (Si) | 14 | CRS |
| Sulfur (S) | 16 | UVS, Plasma, LECP, CRS |
| Iron (Fe) | 26 | CRS |
Voyager did not make any direct measurements of the chemical composition of the clouds, but theorists generally agree that the uppermost clouds are ammonia cirrus, and that layers of ammonium hydrosulfide (NH₄SH) and water exist at deeper levels. All these clouds are formed in the troposphere, the layer of the atmosphere in which convection takes place. The top of the ammonia cloud deck is thought to have a pressure of about 1 atmosphere and a temperature of about -113° C.
Ammonia cirrus is white, yet Jupiter’s clouds display a spectacular range of colors. Voyager did not determine the nature of the coloring agents; they may be minor constituents—trace impurities in a sea of white clouds. Perhaps organic polymers, formed from atmospheric chemicals such as methane and ammonia that have reacted with lightning, are responsible for the oranges and yellows. The color of the Red Spot could be caused by red phosphorus (P₄). According to this theory, phosphine (PH₃) from deep in Jupiter’s atmosphere is brought to high altitudes by the upwelling of the Great Red Spot. Ultraviolet light, penetrating the upper reaches of the Red Spot, splits the phosphine molecules, and, through a series of chemical reactions, converts the phosphine into pure phosphorus. However, this theory fails to explain the existence of the smaller red spots on Jupiter; these spots are not at such high altitudes as the Great Red Spot (which is the highest and coldest of Jupiter’s visible clouds), so it is unlikely that ultraviolet light could react with any phosphine in these areas to produce red phosphorus.
Although the Voyager spacecraft never flew over the poles of Jupiter, it is possible to reconstruct from several images the View that would be seen from directly above or below the planet. Note the absence of a strong banded structure near both poles. The regular spacing of cloud features is obvious. In the Southern hemisphere, the three white ovals are 90 degrees apart in longitude, but a fourth oval at the other quadrant is missing. The irregular black areas at each pole are places for which no Voyager data exist. The resolution of the original pictures from which these polar projections were made was about 600 kilometers.
North pole. [P-21638C]
South pole. [P-21639C]
Various forms of elemental sulfur might be responsible for the riot of color we see on Jupiter. Sulfur forms polymers (S₃, S₄, S₅, S₈,) that are yellow, red, and brown, but no sulfur in any form has been detected on Jupiter. “We never promised you we were going to identify the colors on Jupiter with this mission,” one of the atmospheric scientists remarked, “but we will have a probe that is going into the atmosphere in the mid-1980s—Galileo.” Perhaps the mystery of the Jovian clouds will have to wait till then.
Temperature maps of Jupiter were obtained by IRIS in radiation arising at different levels above the clouds. Maps show temperatures at pressures of 0.8 atmosphere near the clouds, and 0.2 atmosphere near the top of the troposphere. In addition to the low temperatures over the bright zones and the higher temperatures over dark belts, there is a great deal of smaller scale structure. It is interesting that a cold area corresponding to the Great Red Spot is clearly visible even near the top of the troposphere, indicating that this feature disturbs the atmosphere to very high altitudes.