Inner planets = Terrestrial planets

• Terra means "Earth" in Latin

• The four inner planets are called this because of three characteristics:

  • They are smaller than the outer planets

  • They have high densities

  • They have a rocky surface and metallic materials (ex: iron and silicon)

Mercury - "Swift Planet"

• Smallest terrestrial planet

• Closet to the Sun

• Surface has flat plains and craters

• Has no atmosphere

• Temperatures during the day reach 806 degrees; at night it can drop to -274 degrees

Venus - "Morning Star"

• Has a very thick atmosphere

• Atmosphere is mostly CO₂

• Always appears covered in clouds (clouds are mostly sulfuric acid)

• Has the hottest surface of any planet (860 degrees)

• The extreme heat is caused by the atmospheres runaway greenhouse effect

• Greenhouse effect is the trapping of heat by the atmosphere

• Venus has over 10,000 volcanoes on its surface

• The extreme pressure from the atmosphere crushed the first 4 probes sent to Venus

• 1 year on Venus = 7.5 months on Earth

• 1 day on Venus = 8 months on Earth

Earth - "Blue Planet"

• Only planet that life has been found to exist...so far

• Has liquid water on the surface; about 70% of the surface is covered in water

• Earth's distance from the Sun makes the perfect temperatures for life

• Only planet with atmosphere rich in oxygen

• Has a greenhouse effect that keeps the planet warm

Mars - "Red Planet"

• Surface appears red due to iron-rich rocks breaking down and leaving a rusty dirt behind

• Has frozen water ice and evidence of liquid water in the past

• Atmosphere is 95% CO₂

• Temperatures range from -220 - 68 degrees

• Olympus Mons volcano is the largest in our SS; as big as Missouri and 3x the height of Mt. Everest

• Has 2 small moons; Phobos and Deimos

• Most explored and studied planet besides Earth

• NASA currently has 2 rovers, 1 lander, and 1 helicopter exploring the surface of Mars