The Terrestrial Planets 459
15.1 Portraits of the Terrestrial Planets 460
15.2 Mercury 462
Mercury's Temperature and Atmosphere 463
Mercury's Interior 465
Mercury's Rotation 466
15.3 Venus 467
The Venusian Atmosphere 467
The Greenhouse Effect 468
The Surface of Venus 468
The Interior of Venus 472
Rotation of Venus 472
15.4 Mars 473
The Martian Atmosphere 476
The Martian Interior 479
The Martian Moons 480
Life on Mars? 480
15.5 Why Are the Terrestrial Planets So Different? 481
Role of Mass and Radius 481
Role of Internal Activity 482
Role of Sunlight 482
Role of Water Content 482
Role of Biological Processes 482
15.6 Update: Exploring Mars 483