1. Chapter 29 The Solar System
Section 2
Inner Planets
Notes 29-2

3. Inner Planets Terrestrial Planets: Similar to Earth
Solid rock with a metal core
No rings
Number of moons varies from 2 to zero
Covered with impact craters
From collisions with rocky pieces during the later stages of formation

4. Mercury

5. Mercury Closest to the sun Named after Roman god Mercurius
Swift messenger of the gods
Short orbital period = 88 Earth days
One rotation = 59 Earth days
Rotates 3 times in 2 orbits
Speed is about 50 km/s
No moons

6. Mercury
Mariner 10 (1974 and 1979)
Visited Mercury
Surface covered with craters
Craters appear to have hardened lava inside
Mercury was once volcanic
Has changed very little since it was first formed
Hard to see because of proximity to the sun
Sometimes can be seen on horizon at sunrise or sunset

7. Mercury Atmosphere Temperature range Has a week magnetic field
Very thin
Constantly being blown away by solar winds
Gravity is weak and can’t hold gases in
Temperature range
High = 427 °C (during the day)
Low = -173 °C (during the night)
Has a week magnetic field
Core may still be molten

8. Venus

9. Venus Second planet closest to the sun
Named after Venus, Roman goddess of beauty and love
One of the brightest objects in the sky
Third only to the sun and the moon
Known as the “morning star” or “evening star”

10. Venus Orbital Period = 225 Earth days Rotates slowly = 243 Earth days
Rotates in the opposite direction than the other planets
From east to west
No moons
Average surface temperature = 464 °C
Atmospheric pressure = 90 x Earth’s

11. Venus Called Earth’s twin Only volcanically active in few hot spots
Almost the same in size, mass and density
95% of Earth’s diameter
80% of Earth’s mass
Only volcanically active in few hot spots
Large shield volcano called Sif Mons
Carbon dioxide from volcanoes was trapped in the atmosphere

12. Venus Atmosphere 96% carbon dioxide
Allows infrared in but traps it on the surface
Run away Greenhouse Effect
Water boiled off because of high temps
Clouds contain sulfuric acid
Rains sulfuric acid

13. Venus Soviet Union set 6 probes in the 70’s
survived heat, pressure and sulfuric acid long enough to send pictures back
Surface is smooth with some mountains and valleys
Composed mostly of basalt and granite
Magellan orbiter (‘90 & ‘92)
Used radar to see surface
Most common are domes, mountains, volcanoes and lava plains