Planetary atmospheres Chapter 10 Sections 10.1 & 10.2

Planetary Atmospheres Discuss the factors that affected the geologic processes and formations of the planets Outline the information in the 6 slides Use Chapter 10, sections 10.1 and 10.2 , pages 280 - 295 to add further detail. Highlight the detail that you add Refer to your vocabulary to be sure you understand the concepts

Planetary Atmospheres What is an atmosphere? the layer of gases that surround a world can be either molecules or atoms which create pressure-we feel the pressure of 1 atm, on Venus we would feel the pressure of 90 atmospheres Where does the atmosphere end? There’s not a specific ending place-it kind of fades away Earth has different layers which creates air pressure of 1 atmosphere. Atmospheres have an end when the light is not scattered and it is pitch black. However, particles still drift for 1000’s of miles from the surface into space.

Atmospheric Structure 3 factors that determine how sunlight would heat a planet with no atmosphere: 1. Distance from the Sun the closer it is, the more energy from sunlight reaches the surface 2. How much sunlight the planet absorbs vs. reflects 3. How fast the planet rotates if it has a short day, the temperatures will be more even than if there is a really long day

Atmospheric structure How does an atmosphere keep a planet warm? Gases can absorb infrared light and heat up Greenhouse gases trap infrared radiation and this helps heat the lower atmosphere (where we live!) The greenhouse gases are gases that are good at absorbing infrared light: Water vapor Carbon dioxide Methane The greenhouse effect results from trapping of infrared radiation at the lower levels of the atmosphere. Certain gases are better at this than others: water vapor, methane, carbon dioxide.

10.1 Atmospheric Structure Layers of the atmosphere The Earth has distinct layers based on the type of gas prevalent and its absorption of energy.

10.1 Atmospheric Structure How does the fact that our atmosphere scatters light benefit us? What would it be like if our atmosphere didn’t scatter light? Without scattering we would be able to see the stars during the daytime! Also, shadows would be pitch black, so walking down the alley in a big city would be like night! Scattering of light by the atmosphere allows life to see. Without it, day would seem like night.

Atmospheric Structure Why is the sky blue? Light scattering makes the sky appear blue Blue light is scattered while the red light goes straight through the atmosphere The blue wavelengths tend to be more scattered than others

Atmospheric Structure Why do sunsets appear red? Sunlight passes through more atmosphere to reach you-most of the blue light is “scattered away” leaving the red behind. Red wavelengths of light are more scattered through more atmosphere

10.1 Atmospheric Structure Describe how the greenhouse effect works and why it is important to life on Earth. Light from the sun warms the atmosphere and ground The “greenhouse” gases absorb heat, then re-emit it in all directions This helps heat the surface and keeps the troposphere warm Importance? Because it keeps us warm and regulates our temperatures so we don’t have very extreme temperature shifts

10.1 Atmospheric Structure  Why is the stratosphere called the stratosphere?  There isn’t any convection, so the air isn’t moving much and becomes layered-AKA stratified Airplanes glide smoothly here because of the lack of air movement. How does the ozone in the stratosphere benefit us? It absorbs most of the Sun’s UV radiation, which is very damaging to us The stratosphere heats with the absorption of UV by the ozone. The air warms with altitude.

Atmospheric Structure Figure 10.9 Very important!! a. Which one of the three planets shows the biggest temperature increase due to the greenhouse effect? b. Which planet has the most uniform temperature from high to low altitude? c. Is the Earth’s temperature higher at and altitude of 25km or 50km? Venus would be the most affected planet in temperature decrease without a greenhouse effect. Why?

Magnetospheres and the Solar Wind Why is the magnetosphere so important to us? Solar wind = charged particles from the Sun The magnetosphere will either divert those particles or trap them in the Van Allen Belts The magnetosphere of the Earth and other planets makes charged particles pass around the planet so the solar wind does not strip away the atmosphere. The charged particles would also destroy life on planet Earth.

Magnetospheres and the Solar Wind They can produce beautiful auroras in the North and South poles- where the North and South poles of the magnetosphere come close to the Earth’s surface The interaction of the solar wind with the atmospheric causes produces light of different colors depending on gas and levels and amounts of charged particles.

  Weather and Climate What is the difference between weather and climate? Weather is the varying conditions and combinations of wind, clouds, temperature, and pressure Can change with the seasons and atmospheric conditions, can vary dramatically by the month, day or even hour Climate is the long term average of all the weather in an area and generally stays the same over long periods of time Weather is the day to day condition of the atmosphere whereas climate is the average condition of the atmosphere at a particular location over an extended period of time, i.e. hundreds of years.

10.2 Weather and Climate What are the 2 major factors affecting global wind patterns? Atmospheric heating: the air at the equator heats and expands, then flows towards the poles and sinks, creating convection cells Rotation and Coriolis Effect: Coriolis effect alters the path of the air due to the rotation of the Earth like a merry go round All the convection cells with the surface winds are affected by the rotation of the Earth’s surface below them as demonstrated by a merry go round and a ball.

Why would the Earth have more cells than Venus? The circulation of the Venusian atmosphere is dominated by two huge convection currents in the cloud layers, one in the northern hemisphere and one in the southern hemisphere

Weather and Climate What are the 2 major factors affecting global wind patterns? Planetary rotation: basically the rotation of the planet pushes the air sideways-called the Coriolis effect The major factors of atmospheric heating and cooling, causing rising and falling convection currents and the rotation of the Earth causing these currents to change direction due to Coriolis Effect create the global wind patterns.

10.2 Weather and Climate How does the Coriolis effect change the shape and movement of the circulation pattern of winds on Earth? Breaks up the convection cells so there are 6 instead of 2 (3 per hemisphere) Causes air to circulate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere Air deviates to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Atmospheric Origins and Evolution How are atmospheres created? From 3 different processes Outgassing-the outpouring of gases from the earth's interior Evaporation/sublimation-surface liquids evaporate into the atmosphere Bombardment-micrometeorites can create only a very thin atmosphere, this is the main source of atmosphere for the Moon and Mercury The atmosphere is modified by 3 different processes that add to it.

10.5 Atmospheric Origins and Evolution Gaining Atmosphere Outgassing from volcanism on Earth, Venus and Mars releases water, carbon dioxide, nitgrogen and sulfuric gases Evaporation and sublimation from the surface adds gases as the planet surface warms Bombardment by micometeorites ejects surface materials including gases and explains even the small amount of atmosphere around the Moon and Mercury

10.2 Atmospheric Origins and Evolution Losing Atmosphere Thermal escape occurs as particle are heated and reach escape velocity Bombardment and atmospheric cratering result from solar wind particles stripping. Condensation of atmospheric gases on the surface occur with cooler temperatures. Mars has dry ice on its surface Gases chemically react with the surface, like oxygen On the other hand, atmospheres lose gases by several different processes.

Atmospheric Origins and Evolution What are the 3 factors that determine if a gas can be lost by thermal escape? 1. The planet’s escape velocity-the larger the planet the stronger the gravity 2. Temperature-higher temperature means faster movement 3. Mass-it’s easier for lighter particles to move fast enough to escape

Terrestrial Atmospheres  Reflection-Extra Credit! What makes our atmosphere so unique and suitable for life? Give at least 4 pieces of evidence to support your claim. Include information on the atmospheres of at least 2 other terrestrial planets in comparison with Earth. What makes are planet so privileged? Its atmosphere.