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Storms and Spots / Atmosphere
Jupiter is the closest of the four largest planets, also known as the "gas giants" (the others are Saturn, Uranus, and Neptune). Its atmosphere contains huge storm
systems including the Great Red Spot, a storm that has been observed by people on Earth for more than 300 years.
Layers and colors: Jupiter is believed to have three cloud layers in its atmosphere. At the top are clouds of ammonia ice; beneath that ammonium-hydrogen sulfide
crystals; and in the lowest layer, water ice and perhaps liquid water. The vivid colors of Jupiter's storms are probably caused by their chemical content. Although there
isn't much carbon in Jupiter's atmosphere, carbon easily combines with hydrogen and small amounts of oxygen to form a variety of organic compounds. The orange and
brown colors in Jupiter's clouds may be due to the presence of these organic compounds, or sulfur and phosphorus.
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Thunderstorms on Jupiter: Scientists were surprised when the Galileo Probe found much less water than they expected in the top clouds of Jupiter. But it turned out
that the probe's entry site was unusual. Earth-based observations and more recent observations by the Galileo orbiter showed that the probe entry site is probably one of
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the warmest and driest areas on Jupiter. Later, the instruments on the orbiting
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Water Cloud Thunderstorm
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spacecraft confirmed that there are both dry and wet regions on Jupiter. In some large
areas, such as the Probe entry site, air descends and becomes as dry as the air in the Sahara desert. In other areas, the water rises into billowing thunderstorms many
times larger that storms on Earth.
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A rival for the Great Red Spot: During its tour of Jupiter, Galileo scientists observed two large cold storms, called "white ovals", merge to form one larger storm. This
new white oval is the strongest storm observed in our solar system, with the exception of Jupiter's Great Red Spot, and is the diameter of the Earth.
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Lightning: Images of Jupiter's night side taken by the Galileo spacecraft reveal that the planet's lightning is controlled by the large-scale atmospheric circulation and is
associated with low-pressure regions.
…and your little moon too: Okay,
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Jovian Lightning
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so Europa may not be so little - it's the
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smallest Galilean moon of Jupiter but still ¾ the size of Earth's moon - but Galileo
instruments did find a small atmosphere. Learn more about it on our Europa page or in the Europa Q&A area. The Voyager spacecraft previously discovered an
atmosphere on Jupiter's innermost Galilean moon, Io.
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