Earth & Space Systems - Pedagogical Connections: Surface & Atmospheric Properties of the Planets
Investigation and classification of the planets and satellites of the solar system provides the pre-service teachers with an opportunity to explore use of inquiry-based learning and web-based resources while investigating space science content in their studies. The content objectives include recognition of the properties of terrestrial versus gas giant planets, the importance of planetary resurfacing as an indication of important geophysical processes in the interior of planets and satellites and developing an understanding of how the different solar system bodies came to be.There are five major steps in this process.
- The students begin with a table of basic planetary data as can be found in any introductory space science text. They are asked to develop a classification system for the planets which would use physical characteristics to break them into 2 or 3 groups of similar properties. The students must write a testable hypothesis which will support or refute their classification system and utilize the internet to collect data for support or refute their hypotheses (Steps 1 - 4 in the Planets (HTML File 45kB Jun6 05) Assignment). Class discussion results in a classification system that separates the terrestrial planets, from the gas giant planets with Pluto fitting poorly into either category. While multiple properties of the planets are examined, class discussion quickly focuses on density as a primary property relative to secondary properties, such as length of year, which depend on location in the solar system rather than any intrinsic property of the planet type
- The students next focus on the terrestrial planets by visually examining globes of Venus, Earth, Moon, and Mars. They are challenged to identify and account for features which are similar and different on the 4 bodies though a brainstorming process conducted as a class. For sake of completeness, data for Mercury are added by the instructor. Observations include the presence, absence, and density of volcanoes, linear mountain ranges, trenches, rift valleys, glaciers, dendritic valley networks, oceans, craters and an atmosphere. The ultimate objective is for students to recognize that the density of craters poses a question with 3 significantly different explanations.
- A. Planetary bodies of different sizes receive different levels of bombardment by bolides.
- B. Atmospheres can shield planetary bodies from major bolide impacts.
- C. Planetary bodies have differential ability to resurface themselves.
- The students propose hypotheses to explain the differences in impact cratering and utilize the internet to collect data to support or refute their hypotheses. The results indicate that the degree of cratering is inversely related to the mass and diameter of the bodies being investigated regardless of the presence or absence of an atmosphere. Class discussion of the data suggests that hypothesis C is most strongly supported. The accumulated data provide opening discussions on and evidence for several mechanisms of resurfacing driven by both internal and external processes which will be investigated during the course.
- The students continue their investigation by examining the atmospheres of 4 of the planets. Results support multiple methods of atmospheric formation from degassing of planetary interiors (Venus, Earth, Mars) to primary accumulation of nebular gasses during planetary accretion (Jupiter, Saturn). The students efforts ultimately build toward an understanding of temperature conditions in the nebular disk which can explain the composition of the planets at various distances from the sun.
- As a final step, examples of the different types of satellites from earth's moon to the Galilean satellites to representatives of minor moons are divided among the students for a class-wide investigation. The collective data produced provide further support to the nebular hypothesis, planetary classification system and importance of planetary body resurfacing mechanisms. This assignment serves as an opening to discussions of possible extraterrestrial life.