The Inner Planets

1. The Inner Planets

2. Inner planets • The 4 inner planets in order from the sun—Mercury, Venus, Earth and Mars • They are more similar to each other than they are to the five outer planets. • The four inner planets are small and have rocky surfaces. • These planets are often called the “terrestrial” planets. • Terrestrial means “relating to Earth”

4. Inner planets

5. Earth

6. Mercury

7. Mercury • Closest planet to the sun. • Not much larger than Earth's moon. • Has no moons of its own. • So close to the sun so it’s hard to get a good view of it. • Many craters on its surface.

8. Mercury • Has an extremely thin atmosphere. • Planet of extremes. • It’s so close to the sun that during the day, the temperatures can reach up to 430°C. (806F) • It has almost no atmosphere so at night all the heat escapes into space dropping the temperature to −170°C. (-274F) • Greatest range of temperatures than any other planet.

9. Venus

10. Venus • Similar in size to Earth. • Density and internal structure of Venus are similar to Earth's. • However, in many other ways, Venus is very different from Earth.

11. Venus • Takes about 7.5 Earth months to revolve around the sun. • Takes about 8 months for Venus to rotate on its axis. • Venus rotates so slowly that its “day” is longer than its “year.” • Rotates from east to west, the opposite direction from most other planets and moons. • This type of rotation is called retrograde rotation.

12. Venus's Atmosphere • Atmosphere is so thick that every day is a cloudy one. • Pressure of Venus's atmosphere is 90 times greater than the pressure of Earth's atmosphere. • Could not breathe on Venus because its atmosphere is mostly carbon dioxide. • Clouds are partly made of sulfuric acid.

13. The Surface of Venus • Covered with rock, similar to many rocky areas on Earth. • Has volcanoes with lava flows, many craters, and strange domes not found on other planets.

14. Mars

15. Mars • Atmosphere of Mars is mostly carbon dioxide. • Has only 1 percent the pressure of Earth's atmosphere. • Astronomers have found that some water remains on Mars in the form of ice at its north pole. • Mars' south pole has an ice cap made mostly of frozen carbon dioxide.

16. Exploring Mars   • Axis is tilted so Mars has seasons just as Earth does. • Barren and covered with craters like the moon. • Regions of Mars have giant volcanoes. • No oceans or puddles of water exist. • Photographs taken from space do show evidence that water flowed on Mars millions of years ago.

17. Mars's Moons • Mars has two very small moons. • Phobos and Deimos.