4-3 The Inner Planets The Solar System

Vocabulary Terrestrial planet-The name often given to the four inner planets: Mercury, Venus, Earth, and Mars. Greenhouse effect- The trapping Of heat near a planet’s surface by certain gases in the planet’s atmosphere.

The Inner Planets – My planet diary p. 146 What’s in a name? You can find Lewis and Clark’s guide Sacagawea, artist Frida Kahlo, writer Helen Keller, and abolitionist Sojourner Truth all on Venus Almost every feature on Venus is named for a real, fictional, or mythological woman. The person or people who discover an object or feature in the solar system get to choose its name Guidelines: Features on Mercury are named for authors, artists, and musicians. Many craters on Mars are named for towns on Earth. most of the craters on Earth’s moon are named for astronomers, physicists, and mathematicians. Who decides what to name a newly discovered feature in the solar system? _______________________________________________________________ If you discovered a new planet, how would you decide what to name its features? ________________________________________________________ ______

The inner planets are small and dense and have rocky surfaces. often called the terrestrial planets, from the Latin word terra, which means “Earth.” All have relatively high densities Rich in rocky and metallic materials, including iron and silicon Each has a solid surface All have atmospheres, except Mercury Figure 1: Which planet is the largest? _____________________________ Which plant has the most moons? _____________________________ Which planet is most similar to Earth In size? ______________________________ The Inner Planets – what do the inner planets have in common p. 147

Assess Your Understanding pg. 147 I Get It! Now I know that the inner planets are _____________________________________________________ *The inner planets are Mercury, Venus, Earth, and Mars. *Close to the Sun and separated from the much larger Outer Planets by an asteroid belt. *Sometimes called terrestrial planets and are composed of rock. * Due to their hard surfaces, these planets have canyons, craters, mountains, and volcanoes. * Few or no moons. * Developed from small grains of dust that collided and formed together.

Smallest terrestrial planet (not much better than Earth’s moon) and closet to the sun Temperature can range from 430°C to below -170°C Interior probably made up mainly of dense metal iron Surface: Flat plains and craters on its surface Most craters formed early in the history of the solar system Craters have not worn away over time because of lack of atmosphere and water Atmosphere: Virtually no atmosphere Because its mass is so small, its gravity is weak. Particles can easily escape into space Astronomers have detected small amounts of sodium and other gases around Mercury The Inner Planets – Mercury p. 148

Mercury pg. 148 Exploring Mercury: Mariner 10 flew by Mercury 3 times in 1974 and 1975 Mercury MESSENGER has passed Mercury several times, and will begin orbiting in 2011 Figure 2: The photo shows Mercury’s cratered surface. List 3 things a visitor to Mercury would need to bring. __________________________________________________ How many Mercury days are there in a mercury year? (see figure 1) __________________________________________________

Venus pg. 149 Venus has a thick atmosphere, an unusual pattern of rotation, and the hottest surface of any planet. Venus’s Atmosphere Venus’s atmosphere is so thick that it is always cloudy. Venus has a smooth cloud cover made mostly of droplets of sulfuric acid. Venus’s atmosphere has 90 times the pressure than the Earth’s Atmosphere. You would be crushed by the weight! Venus’s atmosphere is mostly carbon dioxide- so you would not be able to breathe. Venus’s Rotation- a day is longer than a year on Venus!!! Venus takes 7.5 Earth months to revolve around the sun(a year). Venus takes 8 months to rotate once on its axis (a day). Venus rotates from east to west, the opposite direction of most other planets and moons. ( This is possibly because Venus was hit by a large object billions of years ago OR maybe because its thick atmosphere has somehow changed its rotation).

Figure 3 Venus pg. 149 These figures show images of Venus taken from space with a camera (left) and radar (right). Radar is able to penetrate Venus’s thick clouds to reveal the surface. The colors in both images are altered to show more details. Infer: Why do scientists need to use radar to study Venus’s surface?_______________________________________________________ Blue regions are flat plains covered by lava flows.

Venus pg. 150 A Hot Planet Venus is closer to the sun than Earth, so it receives more solar energy than Earth does. The thick atmosphere traps the heat so well that, Venus has the hottest surface of any planet. The average surface temperature of 460 degrees celsius is hot enough to melt lead. When heat is trapped by the atmosphere it is called the greenhouse effect. Exploring Venus Venera 7 was the first probe to land on the surface of Venus(1970) and send back data. Magellan Probe (1990) carried radar instruments and mapped the entire surface through the thick clouds confirming a rocky surface, more than 10,000 volcanoes and plains formed by lava flows. Venus Express from the European Space Agency showed how Venus’s clouds form and change.

Solar radiation The Greenhouse Effect pg. 150 Figure 4 Gases in the atmosphere trap some heat energy. Some is transmitted into space. More heat is trapped on Venus than on Earth. Apply Concepts: Look at what happens to heat energy on Venus. Then draw arrows to show what happens on Earth. Radiation absorbed by greenhouse gases Escaping radiation Solar radiation

Earth pg. 151 There is only one planet in the solar system where you could live easily. Earth has liquid water and a suitable temperature range and atmosphere for living things to survive. The Water Planet The Planet Earth is the only planet that has liquid water on its surface(70%). Earth’s Temperature Earth’s temperature is not too hot nor too cold for life on Earth. If Earth was closer (water would evaporate) or farther from the sun (water would be frozen). Earth’s Atmosphere Earth is the only planet with an atmosphere that is rich in oxygen. Oxygen makes up 20% of the atmosphere. Like Venus, Earth experiences the Greenhouse Effect. This makes Earth Warmer.

Mars pg. 152 Mars is known as the “red planet”. Although Mars is too cold for liquid water, it does have water ice now and had liquid water in the past. Mars’s Atmosphere -is more than 95% carbon dioxide It has few clouds that are very thin. Temperatures range from -140 to 20 degrees Celsius. Water and Ice Scientists think that liquid water flowed on Mars at one time. Now the atmosphere is so thin that any liquid would turn into a gas. Water is suspected in the two polar ice caps. Volcanoes There are some giant Volcanoes on Mars. The largest is Olympus Mons which is the largest volcano in the solar system.

Mars pg. 153 Mars’s Moons Mars has 2 very small moons. Phobos- the larger moon is 22 km across Deimos – the smaller moon is 13 km across. Both moons are covered in craters. Exploring Mars Many space probes have visited Mars. Rovers called Spirit and Opportunity found traces of salts and minerals that form in the presence of water. Curiosity is a rover that is currently on Mars. Curiosity collected rock samples for analysis &media_id=

Assess Your Understanding pg a. Name- Which inner planet has the thickest atmosphere? _______________________________________________________ b. Relate Cause and Effect- Why is Venus hotter than Mercury? _______________________________________________________ _____________________________________________________ I get it! Now I know that the inner planets differ in _______________ _______________________________________________________ _____________________________________________________

Earth's Structure Earth has three main layers: the crust, the mantle, and the core. The Inner Planets