Answer questions like ...

1. Earth and Venus are rocky planets of about the same size, but Earth's average surface temperature is about 59° F, while Venus' is 1,350° F, hot enough to melt lead or aluminum. Why the difference?
2. Earth's magnetic field shields us from solar wind and helps hold onto the atmosphere and water. To what do we owe this invisible protector?
3. Earth is the only body in the solar system thought to have oceans of liquid water.

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