Planetary Evolution Module Overview

We live and walk upon the surface of a planet rich with life and the resources to sustain it. Two thirds of the Earth is covered with water, and much of the land is lush with plants and animals. But when we look up to the night sky, the Moon, our nearest neighbor, is clearly quite different. It is cold, riddled with craters, and to all appearances, lifeless. A look at the surfaces of Venus and Mars reveals them to be hellishly hot and bone-chillingly cold, respectively, with little chance of life on them today. How did Earth get to be so different from Venus and Mars? All formed from the same spinning disk of dust and gas, so how did they evolve to such different states? What makes it possible for the Earth to support life? These are the questions addressed in the Planetary Evolution Module.

The Lessons

The Introduction lesson introduces students to the concept of change throughout the natural world, and assesses their current understanding of ideas related to the Earth.

The second lesson, The Planets Take Shape, begins with a computer database activity that allows students to explore the various bodies in the solar system and determine that Venus and Mars are the most like the Earth. Students begin a more in-depth study of the Earth by focusing on its interior. They examine how density-based differentiation of a molten Earth caused the Earth's interior structure and learn how heat is generated in the Earth's interior. Students add planetary data to the timeline that they started in the previous module. Additionally, Earth's Cousins, the Planetary Evolution module project, is available as an extension. Students are assigned a component of the project after each lesson group, and then present their poster projects in lesson six.

In the third lesson, Surface Changes, students move outward from the Earth's interior to its surface, focusing on plate tectonics. They study patterns of geologic activity to delineate plate boundaries, and explore the rate of plate motion. Students use the rate of plate motion and fossil and glacial evidence to reconstruct the supercontinent Pangea. The mechanism of plate motion, plate tectonics, and the rock cycle are analyzed. Finally, students examine surface details to look for evidence of plate tectonics on Mars and Venus, discovering that only Earth currently has active plate tectonics.

In the fourth lesson, Atmospheres and Oceans, students step outward one more time, moving from the Earth's surface to look at its atmosphere and oceans. Students examine comets and volcanic outgassing as possible sources of the gases in the atmosphere, and see how water vapor condensed to form oceans. They study how the atmosphere has changed over time, especially the emergence of oxygen due to photosynthesis, and how oceans became salty. Finally, students focus on the water cycle, and the close interaction between atmosphere and ocean.

In the fifth lesson, The Living Earth, students pull together all that they have learned about the Earth's interior, surface, and atmosphere. They learn about the greenhouse effect and its effects on Earth, Venus and Mars, and conclude that the presence or absence of a global carbon cycle is the main reason for the differences in how the planets evolved. Plate tectonics, the greenhouse effect, and the interconnectedness of a planet's interior, surface, and atmosphere are examined closely. Finally, students focus on how all of these interactions determine whether a planet is habitable or not for life as we know it. They determine what is required for life as we know it, and how scientists look for life in extreme conditions on Earth as well as on other planets in our solar system. This last activity sets the stage for the next module in Voyages Through Time, Origin of Life.

The Closing lesson provides two assessments of students' achievement of the learning objectives for the module: a pencil and paper test and another concept map. An additional day may be added to the closing lesson for the Earth's Cousins Extension Activity student teams to present their poster projects.

I field tested the Planetary Evolution Module. The students and I were very much engaged with the VTT curriculum. The curriculum addresses high interest topics as well as the topics the students have so many questions about. The one aspect of the curriculum that I found the students to enjoy the most was that it was relevant and timely and helped explain the age old question of “how do scientists know that?” The media and activities involved the students in the nature of science and how it progresses to form a logical theory. The content and format of the VTT curriculum involved students in hands-on and minds-on science. The student readers created an opportunity for the parents of students to become involved in the curriculum and learning.

- Linda Selvig, Centennial HS, Boise, ID

Go to Top