What If There Were a Planet Between Mars and Jupiter?

The Arthur Ross Hall of Meteorites

Educator's Guide: Activity

Overview: Between the planets of Mars and Jupiter lies a wide belt of thousands of asteroids. These asteroids formed at the same time as the nine planets. Yet for some reason they remained in pieces rather than accreted to form a planet. Their position in the solar system marks the transition point between the rocky planets of the inner solar system and the gas giants of the outer solar system. Had they accreted they would have formed a planet 1/10th the size of the Earth.

Resource Use
The activity What if there was a Planet Between Mars and Jupiter? challenges students to identify the characteristics that a planet at this transition point would have.

Briefly review with students the characteristics of the planets of the inner and outer solar system. Call on them to describe the asteroid belt and its position in the solar system. Point out that the asteroid belt is the transition point between the rocky planets of the inner solar system and the gas giants of the outer solar system. Have students work in small groups to investigate this question: If the asteroids had accreted to form a planet at the same time and in the same way as the other nine planets, what would its characteristics be?

Have groups consider these questions as they formulate their answers. Encourage students to do research using library and Internet resources to find appropriate data upon which to base their answers.

  1. Would the planet be a rocky or a gassy planet? Could it be a combination of both?
  2. What would you estimate the mass, diameter, and average density of the planet to be?
  3. What would be the average temperature on this planet?
  4. What would be the planet's period of rotation around the sun?
  5. What chemical elements would make up the planet?
  6. Would the planet have an atmosphere? What chemical elements would make up the atmosphere?
  7. Would the planet's surface have craters? Why or why not?

When groups have finished their investigations, have them present their findings to the rest of the class. Suggest groups illustrate their presentation with models, graphics, and drawings.