1. Section 3 – pg 552 The Inner Planets
Chapter 14
Section 3 – pg 552
The Inner Planets

2. Pg 552 Inner Planets: Earth, Mercury, Venus, and Mars
The four inner planets are small and dense and have rocky surfaces
Terrestrial planets: terra means “Earth”

3. Earth Pg 552 Earth has 3 main layers – crust, mantle, and core
Crust: solid rocky surface
Mantle: a layer of hot molten rock
When volcanoes erupt, this material rises to the surface
Core: made of iron and nickel
Outer core is liquid
Inner core is solid

4. Pg 553
Water
Earth is unique in our solar system in having liquid water at its surface
Earth has a suitable temperature allowing water to exist in liquid, gas, and solid forms

5. Atmosphere Pg 553 Earth has enough gravity to hold on to most gases
Our atmosphere is made of oxygen, nitrogen, argon, carbon dioxide, and water vapor

6. Mercury
Pg 554
Mercury is the smallest terrestrial planet and the planet closest to the sun
It is about the size of our moon and has no moons of its own
Probably made of dense metal iron

7. Pg 554
Exploring Mercury
Most of what we know about Mercury comes from a single probe, Mariner 10.
Flew by mercury 3 times in 1974 and 1975
Messenger flew by in 2008 and orbited it in 2010
Mercury has many craters
The image above is from that very Messenger spacecraft, and shows Mercury in natural color (left) and enhanced colors to reveal greater detail and geologic information.

8. Mercury’s Atmosphere Pg 554 Mercury has virtually no atmosphere
High temperatures on the surface during the day cause gases to move quickly, and Mercury’s weak gravity allows these gases to escape into space
We have detected small amounts of sodium and other gases
Temperatures range from 430 C to -170 C

9. Pg 555
Venus
When Venus is visible in the west just before sunset – “evening star”
When Venus is visible in the east before sunrise – “morning star”
Venus’s density and internal structure are similar to Earth’s. But, in other ways, Venus and Earth are very different

10. Pg 555
Venus’s Rotation
Venus takes about 7.5 earth months to revolve around the sun
Its year is 7.5 months long
Takes 8 months to spin on its axis
Its day is 8 months long
Venus rotates east to west, opposite from all the other planets

11. Pg 556
Venus Atmosphere
Venus’s atmosphere is so thick that it is always cloudy there
Clouds are mostly made of droplet of sulfuric acid

12. Pg 556
The pressure of Venus’s atmosphere is 90 times greater than the pressure of Earth’s
Venus’s atmosphere is mostly carbon dioxide
Carbon dioxide in the atmosphere traps the sun’s heat causing surface to be 460oC (hot enough to melt lead)
Greenhouse Effect: the
trapping of heat by the
atmosphere

13. Pg 556
Exploring Venus
Venera 7: first probe sent to Venus in 1970, landed on the surface and sent back info for only a few minutes before being crushed
Magellan: sent in 1990 and mapped the entire surface showing many volcanoes and broad plains formed by flowing lava

14. Mars Pg 557 Mars is called the “red planet”
The reddish color is due to the breakdown of iron-rich rocks, which creates a rusty dust that covers Mar’s surface

15. Mars’s Atmosphere Pg 557 Mars’s atmosphere is 95% carbon dioxide
Mars has few clouds, and they are very thin compared to the clouds on Earth
Temperature on the surface range from -140oC to 20oC

16. Pg 557
Water on Mars
Images of Mars taken from space do show a variety of features that look as if they were made by ancient streams, lakes, or floods
Scientists think that a large amount of liquid water flowed on Mars’s surface in the distant past
Most of Mars water has evaporated and left the planet and the rest is located in the
planet’s polar ice caps, which
contain frozen water and
carbon dioxide

17. Seasons on Mars Mars has seasons due to its tilt
Pg 558
Seasons on Mars
Mars has seasons due to its tilt
During winters, its polar ice caps grow larger as more frozen carbon dioxide covers it
During storms, dust gets blown away from areas resulting in them looking darker

18. Exploring Mars Pg 558 Many space probes have visited Mars
NASA Spirit, Opportunity, and Curiosity
Examined a variety of rock and soil samples
All have found that water was once present
Europe Mars Express
Orbited but never landed
Mars is barren, covered with craters, and shows evidence of ice

19. Pg 558
Volcanoes on Mars
Some regions of Mars have giant volcanoes, but the volcanoes are not currently active
Olympus Mons on Mars is the largest volcano in the solar system
Covers a region as large as the state of Missouri and is nearly three times as tall as Mount Everest

20. Mars’s Moons Mars has two very small, oddly shaped moons,
Pg 559
Mars’s Moons
Mars has two very small,
oddly shaped moons,
Phobos and Deimos
Phobos is slowly spiraling down towards Mars and will probably smash into Mars in about 40 million years

21. Chapter 14 Section 3 Homework - Pg 559

22. 1A. List the four inner planets in order of size, from smallest to largest.

23. 1B. How are the four inner planets similar to one another?

24. 2A. Describe an important characteristic of each inner planet

25. 2B. Compare the atmospheres of the four inner planets

26. 2C. Venus is much farther from the sun than Mercury is
2C. Venus is much farther from the sun than Mercury is. Yet average temperatures on Venus’s surface are much higher than those on Mercury. Explain why.