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Brenn removed two pizzas from the solar-powered oven, while Dara poured glasses of juice. Dara ate hungrily as she thought about Scout's artificial gravity. Without it, the juice would break into drops and float through the air.
SAM interrupted her thoughts. "Prepare for landing on Mars. Mars is a small planet with a diameter of 4,200 mi (6,790 km), about 142,000,000 mi (228,000,000 km) from the Sun. Mars rotates on its axis in slightly more than 24 hours and revolves around the Sun in about 687 Earth days. The planet has two moons. Gravity on Mars is 38% of Earth gravity. A person weighing 100 pounds on Earth weighs only 38 pounds on Mars."
Dara tossed a basketball toward Brenn. "Just think how high I could leap in a game on Mars," she said.
"No basketball hoops have been observed on the planet," said SAM. "Also, players would have to carry air supplies. Mars' atmosphere is mostly carbon dioxide. Temperatures over most of the planet seldom rise above freezing. A winter's day there may be -200J°F (-130??¨&dC).
"Some landforms look like the deserts of the American Southwest. Winds sweep across reddish sand dunes littered with rocks. Except for polar ice caps (mostly of frozen carbon dioxide) the surface is dry, without oceans or rivers. Dust storms stir up soil rich in iron oxide (rust). These storms cover Mars for months at a time and give it a red color. "There are also craters, deep gorges, canyons, and channels that may be dry river beds. Mars may have once had water. A region near the equator has huge extinct volcanoes."
"Let's get started on a plan for Mars, Brenn," said Dara.
QUESTIONS
Help Brenn and Dara plan their exploration of Mars. Look at the sentence parts below. Connect each one on the left with one on the right to form a list of important facts about the planet.
1. Mars appears red
2. The atmosphere is mostly
3. Martian gravity is
4. Landforms include
5. Temperatures on Mars
6. The reddish soil is often stirred
are very cold, reaching -200°F (-130"ˆ&deC) in some areas in the winter.
weak, only 38% of Earth's.
because of the iron oxide in its soil.
carbon dioxide.
up by dust storms.
canyons, extinct volcanoes, and channels that may be dry river beds.
Writing Assignment: Help Dara and Brenn prepare for their exploration of Mars. Write a paragraph that gives them instructions for keeping safe while they explore the surface of the planet.