The Inner Planets

The Inner Planets to Scale 3,031 mi 7,521 mi 7,926 mi 4,222 mi 5.4 g/cm3 5.2 g/cm3 5.5 g/cm3 3.9 g/cm^3

The Sun in the Solar System Gravitational pull of the Sun causes planets and other objects in solar system to orbit the Sun. More than 99% of all the mass in the solar system is in the Sun Shape of orbit is an ellipse Sun is not quite at the center of each orbit

The Inner Planets

Inner Solar System Terrestrial planets Mercury, Venus, Earth, Mars closest to the Sun Rocky crusts and dense mantles and cores Atmosphere on terrestrial planets formed from gas gravity pulls the gases in and keeps them near surface if planet’s gravity is strong enough

Inner Planet Similarities All are a few thousand miles across All are made of rock, with an iron core All are dense (because made of rock) Why do the inner planets share these similarities?

Mercury Orbits once every 88days Smooth plains and many craters Parts covered with lava long ago, forming long, smooth plains Long, high cliffs Virtually no atmosphere

Mercury’s Surface What do you see?

Venus Similar in size and density to Earth Nearest planet to Earth Carbon Dioxide levels in the atmosphere cause the planet to be much hotter than Mercury, Earth, or Mars. Has volcanoes and flat lava plains

Venus’ Surface Sent spacecraft to take pictures from the surface Lasted 2 hr 7 min Found out it was 865°F at the surface! Why so hot?

Venus Through the Clouds You look through the clouds – with RADAR!

Earth Only planet known to have liquid water Only planet known to have life What features of Earth allow it to sustain life? Earth

Mars Wind causes weathering and erosion similar to Earth Has two tiny moons Atmosphere - mostly CO2; air pressure is about 1% of Earth’s Fast winds cause gigantic dust storms

Martian Canyons Largest canyon – 3,000 miles long and 5 miles deep Rocks shrink when they cool. Astronomers think Mars may have cooled quickly after its formation; how might this be used to explain the large canyon?

Comparing the Inner Planets Mercury Statistics Distance from sun 3.2 light-minutes Period of rotation 58 days, 16 hours Period of revolution 88 days Diameter 4,879 km Density 5.43 g/cm3 Surface temperature –173 to 427°C Surface gravity 38% of Earth’s Venus Statistics Distance from sun 6.0 light-minutes Period of rotation 243 days, (R)* Period of revolution 224 days, 17 hours Diameter 12,104 km Density 5.24 g/cm3 Surface temperature 464°C Surface gravity 91% of Earth’s Earth Statistics Distance from sun 8.3 light-minutes Period of rotation 23 hours, 56 min Period of revolution 365 days, 6 hrs Diameter 12,756 km Density 5.52 g/cm3 Surface temperature –13 to 37°C Mars Statistics Distance from sun 12.7 light-minutes Period of rotation 24 hours, 37 minutes Period of revolution 1 year, 322 days Diameter 6,794 km Density 3.93 g/cm3 / Gravity 38% of Earth’s Surface temperature –123 to 37°C

Why do terrestrial planets have atmospheres Why do terrestrial planets have atmospheres? gravity What planet is closest to Earth in size and mass? Venus The coldest terrestrial planet is Mars and the warmest terrestrial planet is Venus.

Venus’ atmosphere is very dense and causes the planet to be much hotter than all of the other planets. The Earth is the only body in the solar system that appears to be able to support life.

Earth’s Rotation Rotation is the spinning of the Earth on its axis. The time for one rotation is 24 hours. Basically one planetary day! Click image to view Earth’s rotation.

Earth’s Revolution A revolution occurs as the earth moves around the sun. Time for one revolution = 365 1/4 days = 8,766 hours Basically one planetary year!

Round One 1. The Earth spinning on its axis. Rotation Revolution 2. Going around a larger body. Rotation Revolution Revolution 3. 24 hours or 1 day. Round One Rotation Revolution 4. Causes the Earth’s seasons. Rotation Revolution 5. Creates a year. Rotation Revolution 6. The moon going around Earth. Rotation Revolution

Identify the motion being shown in each of these pictures Identify the motion being shown in each of these pictures. Each team must write their answers for each figure in the form of a question. Figure #1 Rotation Revolution Planet Round Two Figure #2 Earth Rotation Revolution