The terrestrial planets and their moons
Characteristics of the terrestrial planets
• The four terrestrial planets are Mercury, Venus, Earth, and Mars.
• They are called so because they are Earth like in size and composition.
• They are also sometimes referred to as the inner planets because they are inside of the asteroid belt.
• These planets are small, have high densities, and are made of rocky materials.
Earth
Earth: statistics
• Average distance from the Sun: 1 AU = 9.3 x 107 mi
• Average orbital speed: 29.79 km/s
• Sidereal period: 1 year
• Axis rotation period: 1 days
• Inclination of equator to orbit: 23.5◦
• Diameter: 12,756 km
• Mass: 5.974 x 1024 kg
• Surface temperature range: -130°F to 140°F
• Number of moons: 1
Earth: atmosphere
• Earth’s atmosphere has changed over billions of years
• In the early stages of the Earth the atmosphere was mostly carbon dioxide and water vapor.
• Due to early plant life that use carbon dioxide and give off oxygen, our atmosphere today is mostly nitrogen (78%) and oxygen (21%) gas.
• The atmosphere burns up many meteoroids (shooting star) before the hit the ground.
Earth: magnetic field
• Earth has an invisible magnetic field around it, that protects us from harmful radiation from the Sun and space.
Our Moon
Moon: statistics
• Average distance from the Earth: 238,9000 mi
• Sidereal period around the Earth: 27.32 days
• Inclination of equator to orbit: 6.68◦
• Diameter: 2160 mi = 0.272 Earth
• Mass: 7.35 x 1022 kg = 0.012 Earth
• Average surface temperature range: -180°F to 266°F
The Moon and tides
• It is the Moons gravity that causes the ocean tides.
• The gravity of the Moon pulls on the Earths oceans.
The creation of the Moon
• The Moon was likely created from the debris that resulted from a collision between the Earth and another large object.
Mercury
Mercury: statistics
• Average distance from the Sun: 0.387 AU = 3.60 x 107 mi
• Average orbital speed: 47.9 km/s
• Sidereal period: 88 days = 0.24 years
• Axis rotation period: 58.6 days
• Inclination of equator to orbit: 0.5◦
• Diameter: 4880 km = 0.382 Earth
• Mass: 3.30 x 1023 kg = 0.0553 Earth
• Temperature range: -274°F to 662°F
• Number of moons: 0
Mercury: atmosphere
• Mercury has very small amounts of hydrogen, helium, and oxygen.
• It also has a very weak magnetic field.
• Due to almost no atmosphere and a weak magnetic field it is unprotected from harmful radiation and meteoroids.
Venus
Venus: statistics
• Average distance from the Sun: 0.723 AU = 6.723 x 107 mi
• Average orbital speed: 35.0 km/s
• Sidereal period: 0.615 year
• Axis rotation period: 243 days
• Inclination of equator to orbit: 177.4◦
• Diameter: 7521 mi = 0.949 Earth
• Mass: 4.87 x 1024 kg = 0.815 Earth
• Average surface temperature: 860°F
• Number of moons: 0
Venus: atmosphere
• Venus’s atmosphere is mostly carbon dioxide (96.5%).
• Carbon dioxide is a green house gas that traps heat. This is why the surface temperature is so high.
• No magnetic field
Mars
Mars: statistics
• Average distance from the Sun: 1.52 AU = 1.42 x 108 mi
• Average orbital speed: 15.0 mi/s
• Sidereal period: 1.88 years
• Axis rotation period: 24h 37m 22s
• Inclination of equator to orbit: 25.19◦
• Diameter: 4217 mi = 0.53 Earth
• Mass: 6.42 x 1023 kg = 0.107 Earth
• Average surface temperature: -63°F
• Number of moons: 2
Mars: atmosphere
• Mars’s atmosphere like Venus is mostly carbon dioxide gas (95.3%).
• But unlike Venus the average surface temperature on Mars is -63°F.
• No magnetic field