Planets: Terrestrial Planets, Mercury, Venus

• Planets are celestial bodies that orbit stars
• They do not produce light of their own
• They shine by reflecting the light of the star they orbit

Terrestrial Planets

• Terrestrial planets are rocky and dense
• They have solid surfaces
• Mercury, Venus, Earth, and Mars are the terrestrial planets in our solar system
• Terrestrial planets are located closer to the Sun
• They are smaller in size compared to the gas giants

Mercury

• Mercury is the smallest planet in our solar system
• It is the closest planet to the Sun
• Mercury has a heavily cratered surface, similar to the Moon
• It has a very thin atmosphere (exosphere)
• Mercury experiences extreme temperature variations
• Daytime temperatures can reach 430°C
• Nighttime temperatures can drop to -180°C
• It completes an orbit around the Sun in about 88 Earth days

Venus

• Venus is often called Earth's "sister planet" because of its similar size and density
• Venus has a thick, toxic atmosphere composed primarily of carbon dioxide
• The atmosphere traps heat, creating a runaway greenhouse effect
• Venus has the hottest surface temperature of any planet in our solar system, around 465°C
• Its surface is covered in volcanoes, mountains, and large plains
• Venus rotates very slowly and in the opposite direction to most other planets (retrograde rotation)
• A day on Venus is longer than its year

Earth

• Earth is the only known planet to support life
• It has a diverse environment with liquid water, continents, and a protective atmosphere
• Earth's atmosphere is composed mainly of nitrogen and oxygen
• It has a magnetic field that shields the planet from harmful solar radiation
• Earth has one natural satellite, the Moon
• The Earth rotates on its axis, creating day and night
• It orbits the Sun in about 365.25 days, creating a year

Mars

• Mars is known as the "Red Planet" due to the presence of iron oxide (rust) on its surface
• It has a thin atmosphere, composed mainly of carbon dioxide
• Mars has evidence of past liquid water, including ancient riverbeds and lakebeds
• It has polar ice caps made of water ice and carbon dioxide ice
• Mars has the largest volcano in the solar system, Olympus Mons
• It also has a vast canyon system called Valles Marineris
• Mars has two small moons, Phobos and Deimos

Gas Giants

• Gas giants are large planets composed mainly of hydrogen and helium
• They lack a solid surface
• Jupiter, Saturn, Uranus, and Neptune are the gas giants in our solar system
• Gas giants are located farther from the Sun compared to the terrestrial planets
• They are much larger in size and have more mass than the terrestrial planets

Jupiter

• Jupiter is the largest planet in our solar system
• It is a gas giant composed mainly of hydrogen and helium
• Jupiter has a strong magnetic field
• It has a system of faint rings
• Jupiter is known for its Great Red Spot, a giant storm that has been raging for centuries
• It has numerous moons, including the four Galilean moons: Io, Europa, Ganymede, and Callisto

Saturn

• Saturn is known for its prominent ring system
• The rings are made up of ice, rock, and dust particles
• Saturn is a gas giant composed mainly of hydrogen and helium
• It has a density lower than water
• Saturn has numerous moons, including Titan, which has a thick atmosphere

Uranus

• Uranus is an ice giant composed of hydrogen, helium, and methane
• Methane in the atmosphere gives Uranus its blue-green color
• Uranus rotates on its side
• It has a faint ring system
• Uranus has numerous moons

Neptune

• Neptune is an ice giant composed of hydrogen, helium, and methane
• It has a deep blue color
• Neptune has strong winds and storms
• It has a faint ring system
• Neptune has several moons, including Triton, which orbits in the opposite direction to Neptune's rotation

Dwarf Planets

• Dwarf planets are celestial bodies that orbit the Sun
• They are not satellites of a planet
• They have enough gravity to be round or nearly round
• They have not cleared their orbit of other objects
• Pluto, Ceres, Eris, Makemake, and Haumea are examples of dwarf planets

Pluto

• Pluto was formerly classified as the ninth planet in our solar system
• It was reclassified as a dwarf planet in 2006
• Pluto is located in the Kuiper Belt, a region beyond Neptune containing icy bodies
• It has a thin atmosphere
• Pluto has several moons
• Charon is the largest moon, and is tidally locked with Pluto

Ceres

• Ceres is the largest object in the asteroid belt, located between Mars and Jupiter
• It is the only dwarf planet in the inner solar system

Eris

• Eris is a dwarf planet located in the outer solar system
• It is larger than Pluto

Makemake

• Makemake is a dwarf planet located in the Kuiper Belt
• It is one of the largest Kuiper Belt objects

Haumea

• Haumea is a dwarf planet located in the Kuiper Belt
• It is known for its elongated shape and rapid rotation

Key Differences Between Planets

• Planets have cleared their orbits of other objects, while dwarf planets have not.
• Planets are significantly more massive than dwarf planets
• Size impacts gravitational clearing
• Terrestrial planets are rocky and dense, while gas giants are composed mainly of hydrogen and helium

Planets are celestial bodies orbiting stars, shining by reflecting light. Terrestrial planets like Mercury and Venus are rocky and dense. Mercury, closest to the Sun, has extreme temperatures while Venus has a toxic atmosphere.