Unit II: The Jovian Planets Summarized

• Contrast the properties of the jovian planets.

Read This Material in Your Text:

• Seeds, 5th Edition: Section 7.2, including pages 134 - 135
• Seeds, 4th Edition: Section 5.2, including pages 110 - 111

Read These Notes: The Jovian planets are far from the Sun and therefore receive less solar energy than the terrestrial planets. According to the inverse square law, Jupiter receives approximately 25 times less solar energy than the Earth. The low amount of solar energy received by the Jovians has played an important role in the evolution of the outer solar system.

The Jovians have high mass and low density (average density: 1.24 grams/cubic cm.). Their low density indicates that they are composed of light elements in either the gaseous or icy state. Studies of their spectra indicate that they are mostly hydrogen and helium. They rotate very rapidly. Their rapid rotation and low densities are responsible for their high oblateness.

The high mass of the joins accounts for their high escape velocities(def.) (average: 35 km/sec). This might explain why the joins have thick atmospheres. At atmosphere is a layer of gas that is gravitationally bound to a planet. The high escape velocity of the joins makes it difficult for atmospheric gases to move fast enough to escape the gravitational pull of the planet. In addition, the small amount of solar energy received by the joins, means that the atmospheric gases are traveling very slowly.. another reason why it is difficult for the gases to reach escape velocity. In essence, It might be said that the joins are "all" atmosphere.)

The atmospheres (def.) of the joins are entirely different in composition from those of the terrestrials. They are composed of gasses which are typical of the rest of the universe and solar system. They are composed largely of hydrogen and helium gases, the most abundant gases in the universe. While the atmospheres of the terrestrial planets are noteworthy for their diversity, those of the joins are more uniform in composition. The joins will be studied in more depth in unit 3.

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.

• Jupiter's radius is how much larger than that of the Earth. (ans.)

• How much less energy does Jupiter receive than the Earth. (ans.)

• Why can't Pluto be classified as either a terrestrial or Jovian planet? (ans.)

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.

15. Planet X has a density of 5.4 grams/cm³, a day 40 hours long and an oblateness of .001. How would you classify this planet? Explain your answer
16. The terrestrial planets have atmospheres that are composed of heavy gasses. The Jovian planets have atmospheres composed of light gases. Calculate the molecular weight of carbon dioxide (the gas composing Venus' and Mars' atmospheres) and diatomic hydrogen (the gas composing the atmospheres of the jovian planets). How much heavier is carbon dioxide than diatomic hydrogen.
17. Use the the inverse square law to calculate how much solar energy reaches Neptune compared to the amount that reaches the Earth.
18. EXTRA CREDIT: A day on Jupiter is approximately 10 hours long; the Earth's is 24 hours long. However, in order to appreciate how fast Jupiter rotates, one must consider the enormous size of Jupiter. Calculate the rotational velocity of Jupiter. (Note: This question is only for those of you who like math. You won't be required to do this type of problem on the unit test. Here is a hint to the solution: Use the equation v=d/t where v = velocity; d, the distance traveled during a rotation; and t, the travel time. The distance a planet rotates is its circumference (circumference = x diameter).)

Here are Some OPTIONAL Sites You May Want to Eplore:

• The Nine Planets...A Multimedia Tour of the Solar System