Jupiter

1.Why are there bands and jets on Jupiter?
2.How is heat transported from the interior?
3.Why are jets stable?
4.Why are hotspots and ovals stable?
5.Are clouds passive tracers or active dynamically in causing jets and bands?
6.Why do the clouds have colors?
7.How are clouds formed?
8.What trace chemicals are present?
How are they created and transported?
9.What hazes exist in the stratosphere?
How do they affect deeper clouds?

Atmospheric Science Goals

1.Determine chemical composition
2.Determine structure to a pressure depth of at least 10 bars
3.Determine nature of cloud particles and location and structure of cloud layers
4.Determine radiative energy balance
5.Investigate circulation and dynamics
6.Investigate upper atmosphere and ionosphere

The Almost Star

The critical factor that defines whether a body is a star or a planet is whether or not nuclear fusion occurs within that body. Nuclear fusion is a process that can only occur under conditions of extremely intense heat and pressure, so that individual nuclei (the heavy, central portion of atoms) are slammed together hard enough to overcome the electromagnetic forces that repel them from one another. Atomic nuclei are always positively charged, and positively charged particles repel one another, just at the north poles of two magnets will repel one another.

In a star or a planet, atoms deep within are pushed toward one another by the weight of all the overlying material. If pressures are sufficient and temperatures are high enough (approximately eight million degrees Kelvin), then fusion is ignited, and that body becomes a star. Jupiter would probably need to be about ten times as massive as it is to reach the central temperatures and pressures needed for fusion.

That doesn't mean that Jupiter would be ten times larger, though. In fact, Jupiter is pretty close to as large as a planet can get. The reason is that adding more material to Jupiter increases its gravitational field so as to further compress the material deep within it. So we'd find it very difficult to make Jupiter any larger than it already is.

The Cloud Belts

1.Although theories abound, it is still not known what gives rise to the bright colorations of the Jovian clouds -- for example, the red pigment in the Great Red Spot or the various yellows and browns.

2.The nature of the circulation which gives rise to the east-west, belt-zone cloud structure is controversial.

3.What creates and sustains the various giant weather systems (of which the Great Red Spot is just one example of a whole family of different types of giant eddies).

Why do the winds blow in opposite directions in the bands of Jupiter?

Gas convects from the interior to the surface, and then circulates back down inside. As the gas breaches the upper layers of the atmosphere, half the material falls back down on the equator-side of the convection cell, and half settles back down on the polar-side of the cell. Because the planet is rotating, the coriolis force deflects the polar-side gases easterly, and the equator-side gases westerly in opposite directions. The sense is reversed in the opposite hemisphere.

NIMS Report: The Nature of Jupiter's Cloud Layers

As expected, the main cloud layer on Jupiter is made up of frozen ammonia crystals, and lies at a pressure level of around half a bar (1 bar is the mean pressure at the surface of the Earth). Although anticipated to resemble terrestrial cirrus clouds, the Jovian, ammonia-ice version is made of particles around a hundred times smaller than those in water-ice clouds on Earth.

The ammonia clouds are overlain by a thick haze at much higher levels in Jupiter's atmosphere. This appears to be a photochemical smog made up of liquid hydrocarbon droplets. A similar layer blankets Saturn's moon Titan and prevents us from seeing Titan's surface. Although thinner than Titan's, the Jovian haze is unexpectedly substantial, and varies with time and place across the planet.

There is a thicker cloud layer below both the haze and the ammonia cloud. This may be the theoretically-predicted hydrogen sulphide (as NH4SH) cloud at around the one-and-a-half bar level (one and a half times the sea level air pressure on Earth), or a combination of that and an even deeper water cloud. New data is being acquired to try to resolve this point.

The Composition of Jupiter's Atmosphere

Jupiter's atmosphere is mainly hydrogen, with about 15% helium and a number of minor constituents, the most important of which are measured and mapped by NIMS. Weather on Earth centres around the condensation and evaporation of water. On Jupiter three species, ammonia, phosphine, and water vapour, can condense, making for a remarkably complicated climate.

The new data have shown that water, in particular, is very variable. This helps explain the very low water abundance measured by the Galileo probe when it plunged into Jupiters clouds in December 1995. It happened, by chance, to enter a particularly dry region.

The Great Red Spot

Animation

One of enduring mysteries is, if indeed the Red Spot is a storm, how it has endured for three centuries. We don't know of any storms on Earth that have persisted for as long

So, why do we call it a storm? Because it rotates around like a cyclone on Earth, or a hurricane, and Jupiter is all atmosphere, so ...

Jupiter is very different from Earth, of course, being bigger, made of hydrogen and helium mostly, spinning much faster (10 hr day), having no solid surface. So, maybe we should not expect things to happen the same there as here. Our ability to model the circulation of Jupiter is still primitive. We can get some patterns that look like Jupiter, but not all of them.

If you imagine the swirling that takes place as water moves down a drain, or past an obstacle, that pattern stays in the same place for as long as the conditions are the same. Perhaps there is an obstacle of some sort in Jupiter's deep atmosphere, where we can't see it.

Recent analysis of data from the Galileo Orbiter has permitted a better understanding of the Red Spot. Most astronomers had believed it was a deep mass of cloud. Instead, it has a spiral arm structure of clouds, with gaps between which enable NIMS to see through the GRS into the deep, relatively clear atmosphere below. Futhermore, the cloud structure is higher in the centre by more than 10 km and tilted towards one side, something like a crooked spiral staircase. What seems to be happening is that wet air from the deep atmosphere is rising rapidly in a relatively narrow region in the centre of the GRS, and then spraying out above the tops of the ammonia clouds while rotating, rather like a giant garden sprinkler. In some ways this is similar to what happens in a terrestrial hurricane, but the Jovian storm is much bigger than the entire Earth.

Rings, even

The Lesser Satellites

The Magnetosphere