Lecture 7: Terrestrial Planets

Question 1

Mercury

Answer 1

• Least well observed of the terrestrial planets
• Heavily cratered, biggest being the caloris basin
• Evidence of lava flow
• interior is solid
• weak magnetic field a puzzle
• Long cliffs indicate cooling and shrinking

Question 2

Venus

Answer 2

• Little known about interior
• Very slow rotation, synodic orbital period is same as rotation period
• Surface has continents, volcanoes
• Very few craters
• Hot and dense atmosphere
• 96.5% CO2, sulphuric acid clouds, extreme greenhouse effect
• Denser clouds block more infrared radiation

Question 3

Mars

Answer 3

• Two tiny moons (Phobos and deimos)
• Very thin atmosphere (95.3% CO2)
• atmosphere density is 1% of the Earth’s
• weak magnetic field
• Northern hemisphere lower and much less cratered than southern hemisphere
• Surface is red from iron oxides
• Long canyons and flow features, volcanoes
• Polar caps have frozen CO2
• Water content higher around poles

Question 4

Moon

Answer 4

• 1/83rd mass of Earth
• Largest moon to planet ratio in the solar system
• No atmosphere
• Surface heavily cratered
• Mare much less cratered than highlands
• tidally locked to Earth
• Interior differentiated, but not as extreme as Earth
• Lunar Maria are huge impact basins flooded with lava
• Lunar Highlands are ancient and heavily cratered

Question 5

Summary of Terrestrial Planets

Answer 5

• All had hot and fluid interiors at some time
• Larger terrestrial planets cooled more slowly and had longer lasting techtonic plate activity, also easier tor etain atmosphere
• Higher rotation speed means more weather
• Fewer impact craters on bigger planets