Section 28.2

THE INNER PLANETS

MAIN IDEA• Mercury, Venus, and Earth, and Mars have high densities and rocky surfaces

• This is why we call them the terrestrial planets

MERCURY• Closest to the Sun making it difficult to see from Earth

• 1/3 the size of Earth

• Has no moons

• Atmosphere is replenished by the Sun

• Atmosphere composed of oxygen and sodium

• Surface covered with craters and plains

SCARPS: PLANETWIDE SYSTEM OF CLIFFS

VENUS• 2nd closest to the Sun

• Has no moons

• The brightest planet in the sky

• Often called the evening star

• Rotates very slowly

• 1 day on Venus = 243 Earth days

• Venus rotates clockwise (opposite to most)

• Very similar to Earth in diameter, mass, and density

• Clouds on Venus consist of sulfuric acid

• Greenhouse effect causes the high concentration carbon dioxide in the atmosphere to keep Venus’ surface temperature hot enough to melt lead.

• Venus is the hottest planet

EARTH

• It’s distance from the Sun and nearly circular orbit are perfect for life which allow water to exist in all three states

• It’s mild greenhouse effect and moderately dense atmosphere of Nitrogen and Oxygen are also perfect conditions for life

• Most tectonically active terrestrial planet

• Has one moon

MARS• Called the ‘red planet’ because of its reddish surface

• Smaller than Earth and less dense

• Has two moons: Phobos and Deimos

• Thin atmosphere

• Constant wind and dust storms

SURFACE• Northern hemisphere: cratered plains

• Southern hemisphere: cratered highlands

• Four gigantic volcanoes near equator

• Largest: Olympus Mons

• Ice caps on both poles

TECTONICS• Valles Marineris: 10 times the length of the Grand Canyon

• There is currently NO plate movement. The volcanoes and canyons were caused by hot spots of volcanic activity

• Erosion patterns suggest that water once existed on Mars

MARS CURIOSITY