Critical Thinking

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Critical Thinking
Our Critical Thinking essays are designed with two objectives in mind:

To encourage a higher level of thinking and expression;
To investigate a problem and/or to resolve an issue using the Internet.

There are times when Internet sites may occasionally be unavailable, or may be reorganized. It is good practice to try the site at a different time before you assume it no longer exists. Early morning and late night are good times to access the Internet if you are having trouble downloading images. Also, certain sites are graphically intense, and may take a while to view on your screen.

This activity contains 3 questions.

The issue of ozone depletion in the stratosphere has become a major environmental concern. Answer the following questions using our GeoSearch and Web Links pages, plus the site below:

Why is ozone destruction greatest above Antarctica, rather than, say, the tropics?
At what time of year is the loss most severe and why?
What are the four key processes by which ozone loss occurs (i.e., "The Recipe for Ozone Loss")?
How long ago did ozone concentration begin to fall rapidly?
Do you think that the ozone layer will recover? Why might it take some time, even if all CFCs disappeared overnight?

[University of Cambridge Ozone Hole Tour]

To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

One of the most exciting and controversial scientific announcements of 1996 was the discovery of chemical and morphological traces inside a meteorite that, scientists claim, indicate past life on Mars. The researchers' claim rests on the assumption that the structures and chemical traces in the meteorite were actually produced by living organisms and that the meteorite is actually from Mars. Scientists believe the meteorite is from Mars based on the similarity of gas molecules trapped within the meteorite to the composition of Mars' modern atmosphere as analyzed by the Viking lander. Based on this similarity, scientists infer that the meteorite is a piece of rock that was ejected from Mars' surface during an asteroid impact, fell to Earth, and lay frozen in Antarctica where scientists discovered it. Earth's modern atmosphere is very different from what it was years ago, so why shouldn't the same be true of Mars? Is this a reasonable consideration, and what might it imply about the claim that life once existed on Mars? Write a brief essay answering these questions.

You may want to start by comparing the composition of Earth's atmosphere with that of Mars, especially with regard to oxygen and carbon dioxide. The Mars Pathfinder Lander, which arrived on Mars on July 4, 1997, sent back data on rock composition and meteorological conditions that indicate the past climate of Mars may have been different. The Life on Mars Page is also a good place to begin.

[Mars Source] [Earth Source] [Meteorite Photo Source] [Mars Photo Source]

To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

What causes the aurora borealis and aurora australis (northern and southern lights)? When are auroral events most likely to occur and where can they usually be seen? Do they occur on other planets? To help you answer these questions, visit the aurora-related sites listed at the Exploratorium and then view this aurora movie [2.7 MB].

To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

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