Planets of the Solar System The Habitable Zone

Planets of the Solar System

The Habitable Zone

Orbital Periods • Sidereal Period: A 360° revolution of one celestial body around another as that the object returns to the same position relative to the fixed stars projected in the sky. • Synodic Period: The elapsed time for the repeated cycles for celestial bodies as observed from the Earth's surface; where planets return to the same position in Earth’s sky. • Orbital periods are typically measured in Earth days or Earth years.

Mercury • Closest planet to the Sun • Known since ancient times • Sidereal Period: 87. 89 days • Sidereal Day: 58. 65 days • Surface Temperature: 100 – 700 K (-280 – 800 F)

Mercury • 0. 38 x the radius of Earth • 0. 98 x the density of Earth • Very large iron core • The detected magnetic field indicates the core may be liquid • ~60% of Mercury’s mass is contained in its core • Thick solid crust • Lack of volcanism and tectonic motion

Venus • Second planet from the Sun • Often Called Earth’s Sister Planet • Known since ancient times • Sidereal Period: 244. 7 days • Sidereal Day: 583. 9 days • Average Surface Temperature: 730 K (854 F)

Venus • 0. 95 x the radius of Earth • 0. 95 x the density of Earth • Thinner crust • Volcanically Active • Atmosphere • 90 x more mass than Earth’s • Extreme greenhouse effect

Phases of Planets • Mercury • Difficult to see the full phase

Phases of Planets Venus

Earth • Third planet from the Sun • Sidereal Period: 365. days • Sidereal Day: 1 days • Average Surface Temperature: 290 K (62 F) • 1 Moon

Earth • Solid Inner Core • Liquid Outer Core • Liquid Mantle • Solid, Rocky Crust

Mars • Fourth planet from the Sun • Known since ancient times • Sidereal Period: 686. 9 days • Sidereal Day: 1. 026 days • Average Surface Temperature: 210 K (-82 F) • 2 Moons

Mars • 0. 53 x the radius of Earth • 0. 71 x the density of Earth

Comparing the Inner Planets

Asteroid Belt