Read These Notes: One of the distinctions between terrestrial and jovian planets is their atmospheres. The properties of the jovian atmospheres are:

• The jovian planets are gaseous bodies and therefore essentially all atmosphere.
• They have atmospheres of mostly the light elements hydrogen (H₂) and He.
• Their thick atmospheres represent material from the original solar nebula and date back to the origin of the solar system.
• The thick atmospheres overly a small rocky cored.

Figure 1 illustrates Jupiter's turbulent hydrogen atmosphere. The planet's rapid rotation gives rise to rapidly rotating eddies, similar to hurricanes in the Earth's atmosphere. However, these "storms" are much larger and of longer duration than similar structures in the Earth's atmosphere. The giant red spot, approximately three Earth diameters across, was first discovered by Galileo in the 1600s.

Figure 3:

Credit: JPL/NASA

Figure 2:

The terrestrial planets have uniquely different atmospheres from those of the jovians.

• Their thin atmospheres are are thin, if existent
• Their atmospheres are composed of heavy gases which are not particularly abundant in the universe.
• Their atmosphere are thought to have been formed within the 500 million years of the planets existence after the removal of hydrogen and helium from the inner solar system. (See Solar Nebula Hypothesis)
• The atmsopheres of the terrestrials vary to the degree to which they have evolved
• Conditions on Mercury have restuled in the lack of an atmosphere.
• Mercury has no atmosphere.
• Venus (Figure 2) and Mars have atmospheres which are more than 95% carbon dioxide; and the Earth's atmosphere is unique.
• The only planet in the solar system that can support life, the Earth (Figure 3), has an atmosphere that is 78% nitrogen (N₂) and 21% oxygen (O₂).

The origin of such diversity can be explained by several factors that influence the evolution of atmospheres.

Complete These Self-check Questions: These questions and their answers are designed to help you determine how well you understand this objective and to provide additional instruction.

• How much heavier is carbon dioxide (CO₂) than molecular hydrogen (H₂)?(ans.) HINT: If you need a refresher in reading a periodic table, you should complete this tutorial.

Homework Questions: Answer these homework questions after reading the on-line lecture and the readings in the text. Complete the self-check questions before attempting the homework. Follow the instructions for submitting the homework on this unit homework page.

• There are no homework questions for this objective.

Here are Some OPTIONAL Sites You May Want to Eplore:

• What Happened to Venus and Mars?
• The Atmosphere of Venus (Excellent...but detailed)