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7. If the earth moves at a speed of 30 km per second, how long does it take the earth to move from one line of longitude to the next. Remember, there are 360 lines of longitude.

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group assessment: making deductions
1. We could make direct deductions. Yes No
2. We could give a sensible explanation for human survival. Yes No
3. We could formulate a rule about the distance of planets from the sun. Yes No
4. We could give a sensible explanation for the above. Yes No
5. We could calculate how long it takes the earth to move through one degree of longitude. Yes No
6. We could answer most of the questions independently. Yes No
7. Co-operation in the group was good. Yes No
8. Each individual made a contribution. Yes No

Group judges success of the exercise: ______________________________________

TASK 8

8.1 Mars – a rare planet

Read the facts below and discuss the questions in your groups.

  • Mars has a north and south pole that are white because of frozen snow and carbon dioxide.
  • The length of the day on Mars is only 41 minutes longer than the length of a day on Earth.
  • A year on Mars is however as long as 687 days on Earth. There are two seasons on Mars, summer and winter. During summer there are fierce dust storms, which make the sky appear pink and orange.
  • The dust absorbs energy from the sun and this allows the temperature to rise to 20 degrees Celsius.
  • The atmosphere on Mars is very thin and dangerous ultra-violet rays can thus reach the surface.
  • Scientists believe that long ago there was water on Mars with large rivers and seas. These days there is almost no water left on the surface but they suspect that there is underground water.
  • No photograph shows any sign of life on Mars. Life as we know it can only exist if there is oxygen.

QUESTIONS:

1. Why do scientists think that there was water on Mars long ago?

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2. If there was liquid water on Mars long ago, what can we deduce about the temperature on Mars at that time?

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3. Why is Mars so cold now?

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Source:  OpenStax, Natural sciences grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11077/1.1
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