Unit II: The Jovian Planets Summarized

Read Seeds: Section 5.2

Lecture: 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 jovians accounts for their high escape velocities(def.) (average: 35 km/sec). This might explain why the jovians have thick atmospheres. (It might be said that the jovians are "all" atmosphere.)

The atmospheres (def.) of the jovians are entirely different 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. While the atmospheres of the terrestrial planets are noteworthy for their diversity, those of the jovians are more uniform in composition. The jovians will be studied in more depth in unit 3.

Complete these Self-check Questions:

14. Jupiter's radius is how much larger than that of the Earth. (ans.)
15. Why can't Pluto be classified as either a terrestrial or jovian planet? (ans.)

Homework Questions: (To submit your answers to the homework questions, first copy the questions from this page and paste them into the homework form. Insert your answers below the questions. Fill in the remaining form elements and submit. Your homework will be e-mailed to me. I will return your graded homework to you in the private e-mail of the comm center).

12. 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 (1 point)
13. The terrestrial planets have atmospheres that are composed of heavy gasses. The Jovian planets have atmospheres composed of light gases. Use the periodic table to calculate the molecular weight of carbon dioxide (1 atom of carbon and 2 atoms of oxygen - the gas composing Venus' and Mars' atmospheres) and diatomic hydrogen (2 atoms of hydrogen - the gas composing the atmospheres of the jovian planets). How much heavier is carbon dioxide than diatomic hydrogen. (1 point)
14. Use the inverse square law to calculate how much less solar energy reaches Neptune than the Earth. (1 point)
15. 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 upiter. Calculate the rotational velocity of Jupiter. (Hint:)You will need to use the equation v=d/t where v = velocity; d, the distance travelled; and t, the travel time. The distance a planet rotates is its circumference (circumference = x diameter). (1 point)

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