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