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Classroom Discussion Activity

The Rise of Oxygen

Follow geologists as they hunt for, pickaxe, and test rock samples from the 2.5-billion-year-old Huronian Supergroup, a sedimentary formation in Ontario, Canada. The scientists are in search of an exact record of how much oxygen gas Earth’s developing atmosphere contained at key moments in geologic time. These crustal relics, which have interacted directly with ancient atmospheres, have the power to tell scientists when and how the Earth built up its incredible life-support system to foster more and more complex organisms.

Class Discussion

Establish Prior Knowledge
Ask students what they know about the formation of Earth’s atmosphere. Tell them that this feature story explores the relationships between the Earth, the atmosphere, and their impact on the beginnings of life on our planet.

Exploration
Ask students to take notes while they are watching the video. Use the following questions to guide your class discussion.
• The Earth formed approximately 4.5 billion years ago. Do scientists think the atmosphere formed at the same time? Why or why not?
• How do scientists think the early atmosphere might have formed?
• Why is sulfur so important in determining the age of oxygen?
• What is the correlation between the rise of oxygen and life emerging from the water to populate the land?
• What are some of the data scientists are looking for, and how are they being used to tell the story of oxygen?
• There are no samples of the early atmosphere, so how do scientists learn about it?
• Why is the Huronian Supergroup formation of particular interest to scientists?
• What are some of the techniques scientists used to learn more about the rock samples?

Wrap-up
Use the following questions to wrap up your discussion.
• What questions do you have about the history of life on Earth?
• How might one investigate these questions?

Extend
Students who want to learn more can visit these related links from NASA:

Life on Earth and Elsewhere
http://www.solstation.com/life.htm
Follow the timeline beginning with the birth of our solar system to the beginnings of life on Earth, and read about how NASA scientists use data about Earth’s early evolution to study the possibilities of life elsewhere in the Universe.

The Evolution of the Cosmos
http://cmex-www.arc.nasa.gov/VikingCD/Puzzle/Prebiot.htm
How did the planets form? When did life evolve on Earth? Find out the answers to these questions plus much more on this fun-to-read site.

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