# Chapter 27.3 The Inner Planets

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Chapter 27.3 The Inner Planets
Std. 1a- Students know how the sun, the terrestrial planets, and the gas planets may have been established during the formation of the solar system Std. 4d- Students know the differing greenhouse conditions on Earth, Mars and Venus Objective 1: Identify the characteristics of the inner planets Objective 2: Summarize the features that allow Earth to sustain life

The Inner Planets Planets closest to the sun are: All similar to Earth
Mercury Earth Venus Mars All similar to Earth Metallic cores and consist mostly of rock # of moons vary from 0-2

1) Mercury Planet closest to the sun (no moons)
Orbits (day) the sun every 88 days Rotates (year) every 59 days Heavily cratered Slow rotation and no atmosphere causes a large temperature range (Day: 427°C and Night: -173°C) Orbit = day Rotates = year Made mostly of nickel and iron One the most dense planet in the solar system Very thin atmosphere Metric: 3.7 m/s2 English: 12.1 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 38 pounds on Mercury. Equatorial Circumference Metric: 15,329.1 km

2) Venus 2nd planet from the sun (no moons)
Orbits the sun every 225 days Rotates every 243 days Same size, mass and density as Earth Hottest planet in the solar system Called the morning star because beside the moon it is the bright object in the sky Size: Equatorial circumference Metric: 38,024.6 km Earth: 40,030.2 km Density: Metric: 5.427 g/cm3 Earth = Metric: 5.513 g/cm3

Venus’s Atmosphere 96% carbon dioxide causing a greenhouse effect that heats the surface to 464 degrees C Hottest planet in the solar system Sulfur dioxide droplets in the upper atmosphere creates clouds which reflect sunlight It is the brightest object in the night sky (aside from the moon and sun) Atmosphere = Carbon Dioxide, Nitrogen Gravity Metric: 8.87 m/s2 English: 29.1 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 91 pounds on Venus.

Venus’s Surface Factors
Venus rotates retrograde (east to west) compared with Earth's prograde (west to east) rotation.  On Earth, Jupiter and Saturn, lightning is associated with water clouds, but on Venus, it is associated with clouds of sulfuric acid. Venus is named for the ancient Roman goddess of love and beauty. (Venus is the Roman counterpart to the Greek goddess Aphrodite.) It is believed Venus was named for the most beautiful of the ancient gods because it shone the brightest of the five planets known to ancient astronomers It is thought that Venus was completely resurfaced by volcanic activity 300 to 500 million years ago. More than 1,000 volcanoes or volcanic centers larger than 20 km (12 miles) in diameter dot the surface. Has mountains, volcanoes, lava plains and sand dunes Lots of volcanic activity

Objective 1: Identify the characteristics of the inner planets
How many moons do the inner planets have? 0-2 moons Which planet has the same mass and density as Earth? Venus What % of Venus’ s atmosphere is carbon dioxide? 96%

Earth 3rd planet from the sun (1 moon) Rotation 365 ¼ days
Weathering and erosion continues to change Earth’s surface Earth's diameter is just a few hundred kilometers larger than that of Venus. We are enveloped by an atmosphere that consists of 78 percent nitrogen, 21 percent oxygen and 1 percent other ingredients.  The four seasons are a result of Earth's axis of rotation being tilted degrees with respect to the plane of Earth's orbit around the sun. During part of the year, the northern hemisphere is tilted toward the sun and the southern hemisphere is tilted away, producing summer in the north and winter in the south. Our planet's rapid rotation and molten nickel-iron core give rise to a magnetic field, All of the planets, except for Earth, were named after Greek and Roman gods and goddesses. However, the name Earth is an English/German word, which simply means the ground: eor(th)e and ertha (Old English) and erde (German).

Water on Earth Life on Earth
Atmosphere and distance from the sun allows water to exist in solid, liquid and gas states Life on Earth Earth maintained a moderate temperature during formation = it can support life

Mars 4th planet from the sun Orbital period 687 days
Rotates every 24 hours 2 moons – Deimos and Phobos Same tilt as Earth – has similar seasons to Earth Equatorial circumference: 21,296.9 km Earth: 40,030.2 km Density: Metric: 3.934 g/cm3 Mass: x 1023 kg Gravity: Metric: 3.71 m/s2 English: 12.2 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 38 pounds on Mars. Mars is a rocky body about half the size of Earth.

Active volcanoes = unknown Seismic activity has been detected
Martian Volcanoes Olympus Mons - Largest volcano is 3 times as tall as Mt. Everest The base is the size of Nebraska Reasons for large volcanoes - no moving tectonic plates Active volcanoes = unknown Seismic activity has been detected Mars was named by the Romans for their god of war because of its red, bloodlike color. Other civilizations also named this planet from this attribute; for example, the Egyptians named it "Her Desher," meaning "the red one." Volcanism was active more than 3 billion years ago, but some of the giant shield volcanoes are younger, having formed between 1 and 2 billion years ago. Mars has the largest volcanic mountain in the solar system, Olympus Mons, as well as a spectacular equatorial canyon system, Valles Marineris.

Mars Earth Water on Mars
Pressure and temperature on Mars are too low for water to exist in liquid form Features caused by erosion indicate that water did exist in the past Water on Mars is trapped by polar icecaps Scientists believe that Mars experienced huge floods about 3.5 billion years ago. Though we do not know where the ancient flood water came from, how long it lasted or where it went, In 2002, NASA's Mars Odyssey orbiter detected hydrogen-rich polar deposits, indicating large quantities of water ice close to the surface. In 2004, the Mars Exploration Rover named Opportunity found structures and minerals indicating that liquid water was once present at its landing site.

Objective 2: Summarize the features that allow Earth to sustain life
Why can Earth support life? Earth maintained a moderate temperature during formation What is Mars’s largest volcano? Olympus Mons Why does Mars have large volcanoes? No moving tectonic plates Why can’t water on Mars exist in liquid form? Pressure and temperature is too low