Stardate 09:01:98

The Clouds of Jupiter

This time of year, Jupiter is dominant in the night sky. This massive planet, containing than 70 percent of all the planetary mass in our solar system, is a favorite of amateur astronomers everywhere. It was also the focus of one of first systematic telescopic studies of the heavens.

Since that time, millions of people have gaze through a telescope at this mighty object, four space craft have flown past it, and one small robot craft penetrated a few dozen kilometers into its atmosphere be fore being destroyed. Yet, after all this, no human has ever seen Jupiter. When we gaze at the mighty planet, the only part we can observe is its dense atmosphere.
Most people are familiar with the tan, brown and white bands that constitute its upper atmosphere,but what are they? Are they clouds like those on Earth, composed of water vapor, with perhaps a few traces of some exotic Jovian gas?
The answer is, for the most part, no.

When we began our look at Jupiter two weeks ago, we learned that Jupiter, like the sun, is, composed of mostly hydrogen and helium gas. This should not be surprising. Some 12 or 15 billion years ago, after the energy created by the "Big Bang" had cooled forming matter, the universe was 75 percent hydrogen, nearly 25 percent helium, and one part in 10,000 lithium. All other elements, including the carbon our bodies use for many life processes and the oxygen we breathe, were created later in the explosions of supernova stars. Helium was even detected in the sun before it was ever discovered on Earth. In fact, even the name helium comes from Helios, the Greek word for sun.

Both hydrogen and helium are clear gasses, so why is the king of the planets tan and brown rather than having a clear atmosphere that would allow us to see down to its "surface' of liquid metallic hydrogen?

Part of the answer to that is that although helium almost never reacts with other materials (which is why it is used in blimps - it cannot react with oxygen and thus explode or catch fire), hydrogen can easily react with many different materials. The hydrogen gas in the atmosphere of Jupiter reacts with the trace elements around it, producing methane, ammonia, ethane, acetylene, and hydrogen cyanide. These are the gasses we see when we gaze upon Jupiter's mighty diameter. In fact, much of the outer layer of the Jovian atmosphere is composed of ammonia at temperature of 123 degrees Celsius (-180 F).
Although it has never been observed, models suggest that the layer of clouds beneath this is compose largely of ammonia hydrosulfide at a temperature of around -70 degrees Celsius, or -100 degrees F. The gas breaks apart, forming ammonia and hydrogen sulfide. Hydrogen sulfide is the gas you are smelling when you smell rotten eggs. The smell of Jupiter in this part of its atmosphere must be much like the smell of rotting eggs and glass cleaner. Not a good vacation spot.

Below this layer has the largest ocean in the solar system. But this ocean is not composed of liquid water, as are the oceans of Earth and (most likely) Europe?. This ocean is an ocean of liquid hydrogen. Liquid hydrogen is often used in science classes for free zing flowers and fruit before these objects are shattered with a swift blow.

This tremendous ocean however, has no surface. That is because at this layer, hydrogen reaches what is known as its "critical point," at which time the hydrogen gas is the same density as liquid hydrogen, and the two are indistinguishable. The atmosphere just becomes hotter and more dense, heading toward the center of Jupiter, until it is pure liquid hydrogen.
We have looked deep into the mystery of the atmosphere of Jupiter with the intent to explain the colors that can be seen from Earth. However, one question remains. All the chemicals we have mentioned that can be seen from Earth are white or clear. No one has yet proven why these colors are there, or why the band patterns are so stable.

It may be that the powerful lightning occurring on Jupiter may be changing some of the chemicals we spoke of into organic material. Organic meaning only carbon based, not meaning associated with life. The answer to the question we asked ourselves at the beginning of the article is: No one knows.

Clear skies, and good viewing.

Jim Maynard is the head of the astronomy department at Earth Treasures and has been an amateur astronomer for more than 20 years. He is a physics student at Keene State College and leads star parties at Wheelock Park in Keene, New Hampshire. If you have any questions about astronomy or star gazing, call him at 603-352-7192.

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