Inner Overview
The Planets
PSC 152
In this section:
What are the charcteristics of each planet? What are the common characteristics? How do these properties relate to each other?
Major Characteristics
What are the major characteristics of each of the inner planets? Review from last lecture
Mercury
Mercury
smallest inner planet looks like Moon (gray, bare, cratered) essentially no atmosphere
Venus
Venus
a dense CO2 atmosphere, covered with deep sulfuric acid clouds, hottest planet, immense volcanic peaks tower over desolate plains
Earth
Earth
Great variety: blue seas, white clouds and ice caps, red deserts, green jungles, mountains Life!!
Mars
Mars
Thin CO2 atmosphere vast red deserts with craters and dunes, polar caps of ice and CO2, canyons and dry river beds, ancient volcanoes,
Commonalties
What do they all have in common? What caused these characteristics?
Commonalities
have similar sizes and structure
Iron/nickel core Rocky mantle and crust
Earth formation
How did Earth's structure form? Video review ...
From Nova Origins mini-series
Commonalties
What caused this common structure?
They are formed in the inner part of the solar system from the same material Solid material formed clumps Gases pushed away by the Sun Differentiation Cooling and cratering See fact sheet
Differences?
What makes each planet unique? What caused these differences in the characteristics of each inner planet?
"Why?" is most important
Memorizing differences is hard and meaningless Understanding the reasons gives meaning to the facts and makes it easier to remember them
Overview
Role of Mass and Radius
Mass and radius affect interior temperature Smaller => not as hot internally This in turn determines the level of tectonic activity Smaller => not as active Examples: Mercury the least active, then Mars, then Venus and Earth
Role of Internal Activity
Internal activity affects the surface More activity => more lava on the surface More lava => features are erased more often Internal activity also affects a planet's atmosphere volcanic gases are the most likely source of gases Less activity => less gas
Role of Mass and Radius
Mass and affect radius atmosphere Low mass Mercury and Mars will have a smaller source of gas than Venus/Earth the low surface gravity of these small planets also means they will have trouble retaining the gases they generate Examples: Mercury the least atmosphere, then Mars, Then Venus/Earth
Role of Sunlight
Heating depends on planet's distance from Sun closer => warmer further => cooler Example: Mercury daytime side is very hot Mars daytime side is much colder
Role of Sunlight
Heat and high energy light from Sun can alter atmosphere Break apart molecules Drive off light gases Example: Mercury, lost most of the little atmosphere it had Venus, UV breaks H2O apart with the H escaping into space
Role of Atmosphere
While temperature affects the atmosphere, the opposite is also true... Atmosphere affects the temperature: warming by greenhouse effect Examples: Venus is hottest Earth is warmer than Moon
Role of Atmosphere
Atmosphere can affect surface: Protects against impacts Wind erosion covers impact craters Examples: Mercury, Mars, and Moon many impacts craters Earth, Venus, not as many, not as visible
Role of Water Content
The water near Earth's surface makes possible many chemical reactions not found elsewhere Examples: Biological processes !!! CO2 removed from atmosphere by dissolving in w...