Lecture 12

Question 1

What is an atmosphere?

Answer 1

An atmosphere is a layer of gas that surrounds a planet

Question 2

What is the composition of the Earth’s atmosphere?

Answer 2

Mainly nitrogen and oxygen. No hydrogen- it is too light
(the atmosphere is also about 10km thick)

Question 3

What are the effects of atmospheres?

Answer 3

-create pressure allowing liquid water to exist
-absorb and scatter light
-create wind, weather and climate
-interact with the solar wind to create a magnetosphere
-make planetary surfaces warmer (greenhouse effect)

Question 4

How does energy from the sun and radiation affect planetary temperature?

Answer 4

Planetary temperature is determined by the balance between energy absorbed from the sun and outgoing thermal radiation

Question 5

How are reflectivity and temperature related?

Answer 5

-A planet’s reflectivity is called its albedo.
-Low albedo temperatures absorb more sunlight –> higher temperatures

Question 6

What is the greenhouse effect?

Answer 6

-Visible light passes through the atmosphere and warms the surface.
-Infrared light from the surface is absorbed by the atmosphere, trapping the heat

Question 7

How do different wavelengths of light interact with the atmosphere?

Answer 7

-x-rays and UV wavelengths are mostly absorbed by the atmosphere
-Visible light can pass through
-Infrared light is trapped beneath

Question 8

What is the troposphere

Answer 8

-lowest layer
-warmed by the IR irradiated by the Earth’s surface

Question 9

How is the stratosphere warmed?

Answer 9

Warmed by the UV from the sun

Question 10

How is the thermosphere warmed?

Answer 10

Warmed by x-ray and UV from the sun

Question 11

Where is the exosphere?

Answer 11

Fades into space

Question 12

Why is the sky blue?

Answer 12

The atmosphere scatters blue light from the sun to make it appear like it is coming from different directions

Question 13

Why are sunsets red?

Answer 13

Sunsets are red because red light scatters less

Question 14

How does the magnetic field protect the Earth?

Answer 14

The Earth’s magnetic field protects us from solar wind

Question 15

What is weather?

Answer 15

Daily variation in the wind, clouds, temperature and pressure

Question 16

What is climate?

Answer 16

Long term average weather of a planet

Question 17

What are circulation cells?

Answer 17

The hot and cold of the equator and poles produce circulation cells

Question 18

What are the 4 factors effecting the atmosphere?

Answer 18

1. Solar brightening: increasing the amount of sunlight warms planets (billions of years)
2. Changes in axis tilt: larger tilts produce more extreme seasons. Smaller tilts keep the poles colder
3. Changes in reflectivity: high reflectivity=cool planet
4. Changes in greenhouse gases: more greenhouse gas=more warming

Question 19

How are atmospheres formed?

Answer 19

-outgassing from volcanoes
-evaporation of surface liquid or the sublimation of surface ice
-impacts of particles and photons

Question 20

How are atmospheres lost?

Answer 20

-molecules approach escape velocity
-condensation of gasses onto the surface
-chemical reactions with the surface
-large impacts that blast gas into space
-solar wind blows gasses away

Question 21

Do the Moon and Mercury have atmosphere?

Answer 21

The moon and Mercury have very thin atmospheres that come from gases ejected by impacts

Question 22

What are the seasons on Mars like?

Answer 22

The ellipticity of Mars’ orbit makes the seasons more extreme in the southern hemisphere

Question 23

What is contained on the polar ice caps of Mars?

Answer 23

-the residual ice of the south cap in the summer is primarily water ice
-carbon dioxide ice sublimates as summer approaches and condenses at the opposite pole

Question 24

How has climate changed on Mars?

Answer 24

-Mars has not had widespread surface water for 3 billion years
-The greenhouse effect probably kept the surface warmer before that time
-Somehow Mars has lost most of its atmosphere

Question 25

What is the atmosphere of Venus like?

Answer 25

-Venus has a very thick carbon dioxide atmosphere with a surface pressure of over 90x that of the Earth
-Strong greenhouse effect
-Slow rotation=Coriolis effect and little weather

Question 26

What does the Runaway greenhouse effect tell us?

Answer 26

That is Earth moved into Venus’ orbit oceans would evaporate and carbonate rocks and release CO2 making Earth hotter than Venus

Question 27

Why is the Earth’s atmosphere so different?

Answer 27

-Located in the habitable zone- zone around a star where liquid water exists
- With life CO2 decreased and O2 increased
-O2 is converted to ozone to produce the ozone layer
-The moon is locked in a stable orbit

Question 27

How does an aurora occur?

Answer 27

Charged particles from the solar wind interact with the Earth’s magnetic field and then interact with particles in the atmosphere

Question 28

Why did the Earth retain most of its outgassed water?

Answer 28

It is far enough from the sun to maintain liquid water- the habitable zone

Question 29

Why does the Earth have so little atmospheric CO2 compared to Venus?

Answer 29

CO2 was absorbed into the ocean and also converted into shells

Question 30

Why does Earth’s atmosphere consist of mainly nitrogen and oxygen?

Answer 30

Lighter elements escape

Question 31

Why does Earth have an UV absorbing stratosphere?

Answer 31

The ozone layer is good at trapping UV radiation

Question 32

How do CO2 levels change in the atmosphere with temperature?

Answer 32

-Cooling allows CO2 build up in the atmosphere
-Heating causes rain to reduce CO2 in the atmosphere

Question 33

What are the factors that cause long-term climate change?

Answer 33

-Changes in the axis tilt
-Widespread ice tends to lower global temperatures
-CO2 from outgassing will build up if oceans are frozen; raising global temperatures again
-Melting permafrost releases CO2

Question 34

Consequences of global warming

Answer 34

-More numerous and intense storms
-Rising sea levels
-Effects on food and water
-Social unrest