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The Planetary Bodies of Our Solar System Debate


This activity is based on the Great Planetary Debate, developed by Jennifer Bergman. Kathy Ellins adapted it for use in TXESS Revolution PDA 5, Earth as a Habitable Planet. You can find the activity in its original form on the Windows to the Universe website. It is one in a large collection of excellent earth science educational activities available online. If you used the adaptation provided here instead of the original, please cite as shown below.

How to cite this work: Ellins, K. (2011), The Planetary Bodies of our Solar System, TXESS Revolution,, Date Accessed.


The sun is at the center of a huge rotating system of eight planets and five dwarf planets, their satellites, and many other smaller bodies. Each planetary body moves in an elliptical orbit in response to the sun’s gravitational force. All travel in the same direction around the sun. About 99.85% of the mass of our solar system is contained within the sun.

The planets fall into two groups. The terrestrial planets—Mercury, Venus, Earth and Mars—are relatively small and rocky. Earth is the largest of the terrestrial planets. The Jovian planets--Jupiter, Saturn, Uranus and Neptune – are enormous gas giants. Size is the most obvious difference between the terrestrial and Jovian planets.  Density, chemical composition, and rate of rotation are other ways in which the two groups differ.  The structure of the interiors of the two groups of planets and their atmospheres also set them apart. Pluto and Eris, the largest dwarf planet discovered in the January 2005, do not fit neatly into either category.  Pluto, which is small and cold, was classified as a planet from its 1930 discovery until 2006. It is member of a distinct population called the Kuiper belt.  Eris is a part of the scattered disc, a distant region of the solar system.

Earth is unique among the planetary bodies of our solar system.  Plate tectonics, at least the recycling kind that currently operates on our planet, is unique to Earth. Although the planetary bodies of the solar system exhibit magnetism, not all have a magnetic field like Earth. Water exists at its surface in all three states—solid, liquid and gas. Water is an essential ingredient for life, as we know it. And life, at least terrestrial life, could not survive on Earth without the magnetic shield that protects us from the charged particles of the solar wind. Our Earth is a habitable planet. 

Development and Testing

This activity was implemented in the following teacher professional development workshops: (1) TXESS Revolution PDA 5C (2009); (2) TXESS Revolution PDA 5C (2009). The National Science Foundation Opportunities for Enhancing Diversity in the Geosciences program funded these PDA’s under NSF Grant No. 0703687. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or the Texas Education Agency.

Activity rating by TXESS Revolution Teachers in PDA # 2009

TXESS Revolution teacher pre and post-TEKS survey ratings reflect teachers’ increased comfort teaching the standards listed after doing the activity PDAs 5B and 5C.