Mars for Earthlings > Lesson Modules > Birth of Planets

Birth of Planets


This learning module and related laboratory exercise exposes students to planetary body classification, and planet differentiation. Students will be able to compare and contrast the formation history of Mars and Earth as well as confidently assess the present classification of the planet Pluto.

Learning Goals

Students will be able to:

  • Explain how planets form using JELL-O 1-2-3 as an analogy
  • Engage in a positive interactive debate regarding the classification of Pluto and in written format express their view competently using current scientific theory and resources.

Context for Use

This learning module is meant for adaptation in an introductory earth science course and/or planetary science course.

Description and Teaching Materials

Compiled In-Class Activities and Homework

In-Class Activities


Teaching Notes and Tips

JELLO 1-2-3 Analogy

  1. Small class size <20: have JELLO ingredients made up and ready for disbursement at end of class for at Homework.
  2. Large class size >20: have both ingredients and one pre-made JELLO cup for students to analyze and develop an analogy for planet differentiation

Pluto debate

  1. Prior to class assign students to either the Affirmative or Negative team so students have a chance to develop an argument. OR
  2. During class, allow students 10-15min to develop an argument

General Comments

  • We have found it very beneficial to invite a guest lecturer from the Physics department to present this material. Students responded well with a myriad of questions.
  • The JELLO 1-2-3 recipe is quite fickle and may not always form 3 layers. Allow some time to figure the recipe out.


  1. After in-class debate, students will write up a short 1 page cited discussion paper on their opinion regarding the classification of Pluto (see link for paper guidelines). Make sure students include and discuss the current planetary classification scheme.
  2. Students will develop an analogy, as a class, between JELL-O 1-2-3 and planetary differentiation

References and Resources

  1. Planetary Differentiation and Planet Comparison Overview:
  2. Jello 1-2-3 recipe:
  3. Mars vs. Earth size research: Brandon, Alan 2011. Nature 473, 460–461 (26 May 2011) doi:10.1038/473460a
  4. Pluto and Planetary Body Classification :
  5. New Horizon Probe to Pluto NASA Video (see homepage for link) :
  6. Kuiper Belt and the Oort Cloud information: