1. Venus

2. The Second Planet Earth’s “sister planet”, is slightly smaller and has similar composition. A collision to the early Venus causes it to rotate in the opposite direction of other planets. Tidal friction has slowed Venus to have one Venusian day almost equal to the year.

3. Clouds Like Earth, Venus is terrestrial with an atmosphere. Clouds on Venus block its surface from view. –High albedo: Venus (0.65), Earth (0.37)

4. Orbital Craft In 1990-94 Magellan orbited Venus. –Radar measurement –Atmosphere measures during deorbit In 2005 Venus Express was launched.Venus Express –ESA mission –Atmosphere probes

5. Penetrating the Clouds Radar can penetrate clouds. –Radio waves –Earth and orbiters Spacecraft can enter the atmosphere of Venus and photograph the surface. –Venera 13 (1981)

6. Volcanos and Lava Volcanos act to cool down the interior of planets. Venus shows evidence of volcanos and lava flows. Lava brings minerals from the mantle to the crust. Gases include carbon dioxide, sulfur dioxide and water. lava gases

7. In the Clouds The clouds of Venus are made of sulfuric acid. –High winds –Polar vortex –Lightning Hydrogen is being lost from water breakup.

8. Early Atmosphere Venus Start with nitrogen, water, carbon dioxide. The sun evaporated the water. Volcanic carbon dioxide and sulfur dioxide and chlorine entered the atmosphere. Atmospheric pressure increased to 100 times Earth, temps to 460 ºC (860 ºF). Earth Start with nitrogen, water, carbon dioxide. The atmosphere rained water into oceans. Ocean water absorbed volcanic gases. The greenhouse effect remained mild on Earth.

9. Ultraviolet Light Astronomers discovered that chlorine in the atmosphere of Venus causes oxygen to break up so no ozone forms. Without ozone in the atmosphere, UV light comes through and sulfuric acid clouds form on Venus. This discovery led to the understanding that CFCs were causing a hole in the ozone layer on Earth!