The Atmosphere of
Jupiter

[Note: Some excellent new pictures of Jupiter appear here, many made possible by the Cassini mission on its present path to Saturn as it passed by Jupiter!] Check out these which show Jupiter with its moon Io in front: cool pic 1 and cool pic 2

The outermost layer is composed primarily of ordinary molecular hydrogen and helium which is liquid in the interior and gaseous further out. The atmosphere we see is just the very top of this deep layer. Water, carbon dioxide, methane and other simple molecules are also present in tiny amounts.

Three distinct layers of clouds are believed to exist consisting of ammonia ice, ammonium hydrosulfide and a mixture of ice and water. However, results from the Galileo probe show only faint indications of clouds (one instrument seems to have detected the topmost layer while another may have seen the second). But the probe's entry point (left) was unusual -- Earth-based telescopic observations and more recent observations by the Galileo orbiter suggest that the probe entry site may well have been one of the warmest and least cloudy areas on Jupiter at that time.

Data from the Galileo atmospheric probe also indicate that there is much less water than expected. The expectation was that Jupiter's atmosphere would contain about twice the amount of oxygen (combined with the abundant hydrogen to make water) as the Sun. But it now appears that the actual concentration much less than the Sun's. Also surprising was the high temperature and density of the uppermost parts of the atmosphere.

Jupiter has a very complex atmosphere. It is dominated by colorful bands and turbulent swirls, as illustrated in the following two images.

Storms in the atmosphere of Jupiter (Ref and Explanation) Jupiter and Io with Ganymede's shadow on Jupiter (Ref)


Zones and Belts

All that we see is the top of the atmosphere. The light bands are called zones and the darker bands are called belts. The zones tend to be white or yellow, while the belts are often some shade of reddish brown. Temperature measurements by the Pioneer spacecraft (1973) established that the temperature of the dark belts is higher than that of the light zones, implying that the former are lower in the atmosphere. Thus, the belts appear to be regions of descending gas and the zones are regions of rising gas.

Each hemisphere has around 6 bands with winds blowing at very high velocities in opposite directions. This accounts for the extensive shear and turbulence at the boundaries between these regions (see the next section on the Great Red Spot). Large lightning bolts and extensive aurora have been observed in the Jovian atmosphere, as we will discuss further when we consider Jupiter's magnetic field.

The Great Red Spot

The most prominent feature is the "Great Red Spot", which may be seen on the right of the upper left image, just below the equator, and in the two images shown below. As we shall discuss in the next section, it is a kind of large and persistent storm driven by Jupiter's internal heat source.

Jupiter with two moons seen against its surface Jupiter's clouds near the Great Red Spot


The Color of the Atmosphere

The explanation for the color of Jupiter's clouds is still something of a mystery. Although there are compounds in Jupiter's atmosphere that could account for the colors if the atmosphere were warmer, they should not be the colors that are observed at the very cold temperatures in the tops of Jupiter's clouds (about -150 degrees Celsius). It has been suggested that the colors result either from colorful hydrogen compounds welling up from warmer regions, or from colorful compounds associated with trace amounts of elements like sulfur in the atmosphere. Consultation of past observations of Jupiter indicates that the clouds change their colors over time.

More on the Galileo Probe and Orbiter

The Galileo Project has generated large amounts of new information about Jupiter and its moons. The interpretation of the information sent back by the probe that plunged into the atmosphere yields valuable insight, as have the extended observations from the Galileo orbiter. The mission ended Sept 21, 2003: here is more info.

Comet Shoemaker-Levy 9 Impacts Jupiter

Comet Shoemaker-Levy 9 was discovered by Eugene and Carolyn Shoemaker and David Levy in 1993. Shortly after its discovery it was determined to be in a highly elliptical path near Jupiter and on a collision course. It was difficult to calculate its orbit prior to its 1992 pass near the giant planet.

In 1992, SL 9 passed by Jupiter within the Roche limit. It was broken into at least 21 separate fragments which were dispersed several million kilometers along its orbit.

Here are some pictures fragment G impact. Note that the fireball is obsevered 12 minutes after impact. top 20 images of the impacts of fragments.

The estimates of size and mass of the original body and the individual fragments range from 2 to 10 km in diameter for the original body and from 1 to 3 km for the largest fragments.

Between 16 July 1994 and 22 July 1994 the fragments impacted the upper atmosphere of Jupiter. This was the first time that scientists had an opportunity to witness the collision of two extraterrestrial bodies. The impacts were observed by virtually every large ground based telescope, thousands of small and amateur telescopes, and several spacecraft including HST and Galileo. The pictures were posted to the Net within hours of the impacts and caused severe overloading on some ftp and WWW sites. The after-effects of the impacts were visible on Jupiter for nearly a year after the event.

Each fragment hit with about 60km/sec velocity and released energy equivalent 3 million of megatons of TNT. This would be equivalent to 30 million Hiroshima bombs(!) or 30 times the total available nuclear weaponry on Earth.