The Atmosphere Appearance control contains settings for the on-screen appearance of an object's atmosphere.
The checkbox on the left of the control determines whether the atmosphere of the object is displayed. Atmospheres may appear as a colored haze (such as the Earth's atmosphere), or may be so thick that they obscure the surface of the object (such as Venus' atmosphere). Turning off the visible atmosphere can allow the user to see the surface more clearly.
The color setting on the right of the control sets the color of the atmosphere. For known terrestrial planets in the Solar System, including Venus, Earth, and Mars, the Default color of the planet's atmosphere is set by the Universe Sandbox database to match the known appearance of these planets. For other terrestrial planets, the atmosphere color is randomly generated.
The Atmosphere Appearance control is located in the Layers section of the Appearance tab of an object's properties panel.