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Pluto looked small, compared with the gigantic planets that had come before it. "I wonder if Pluto is really not a planet at all, but a moon escaped from Neptune's gravity," said Brenn.
"It certainly isn't anything like the other Outer Planets," replied Dara.
A familiar voice entered the conversation. "Pluto is 3,660,000,000 mi (5,900,000,000 km) from the Sun. It is 1,430 mi (2,300 km) in diameter, smaller than Earth's moon. Pluto spins on its axis once every six days and nine hours. A revolution around the Sun takes Pluto 248 years. Pluto's single moon Charon is half as large as Pluto itself. Gravity on Pluto is very weak. A person who weighs 100 pounds on Earth will weigh only four pounds on Pluto."
"Better wear the ultra-heavy shoes," said Brenn. "Otherwise, we could accidentally bounce high off the surface as we walk."
SAM continued. "It is probably dark on Pluto, for the Sun may appear in its sky simply as a bright star. It is dangerously cold there, about -380LºF (-230 "ˆ˜ "C) most of the time. Pluto's surface may be covered in methane ice. When the planet is closest to the Sun, some of this ice may melt, creating a very thin atmosphere of methane gas."
"Let's find those freezeproof environmental sample containers," said Dara, "and the subarctic suits." After their exploration of Pluto, Brenn and Dara's mission was complete. Now they and you know a great deal about all the planets in our solar system.
QUESTIONS
Draw some conclusions about the planets as you answer the questions below.
1. Which of the nine planets is the smallest? ___________ The largest?____________
2. Which has the hottest temperature? _________________ The coldest?__________
3. Which planet has the strongest gravity? _____________ The weakest?___________
4. Which planet do you think is the most dangerous for explorers? Why? _____________
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5. Which planet do you think is the most likely to have intelligent life forms? _________
Writing Assignment: On the back of this sheet, explain why you think your answer to question 5 is right. Describe what the life forms might look like and why. Begin your essay with a sentence like this: I think _________________________ is the planet most likely to have life forms.