lesson 6 atmospheres

Lesson 6 Atmospheres

Atmospheres

Atmospheric compositions• Venus – CO2 (96.5%), N2 (3.5%), SO2 (0.015%)

• Mars -- CO2 (95.3%), N2 (2.7%), Argon (1.6%), O2 (0.13%)

• Earth – N2 (78.1%), O2 (20.9%), Argon (0.9%), Water vapor (0.4%), CO2 (0.04%)

• Earth is very different than Venus and Mars.• Where is all the CO2 on Earth?

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33% 33%33%1. Plants changed it into

oxygen2. It is in the atmosphere3. It is locked up in rocks.

It is in rocks like limestone• CO2 readily dissolves in water. When it rains CO2

is mixed into water droplets.• This caused the ocean to be mixed with CO2.• When rocks such as limestone form at the

bottom of the ocean the CO2 becomes trapped in the rocks. This is in part due to CO2 trapped in organisms.

• If all the CO2 were released back into the atmosphere from the rocks that contain it, the composition of the Earth’s atmosphere would be almost identical to Venus and Mars.

Atmospheric compositions• Venus – CO2 (96.5%), N2 (3.5%), SO2 (0.015%)

• Mars -- CO2 (95.3%), N2 (2.7%), Argon (1.6%), O2 (0.13%)

• Earth – N2 (78.1%), O2 (20.9%), Argon (0.9%), Water vapor (0.4%), CO2 (0.04%)

• Earth is very different than Venus and Mars.• The liquid water cycle on Earth is the main

contributor to the lack of CO2 in the atmosphere.

• On Earth, when volcanoes erupt they release large quantities of CO2

• Why do eruptions on Earth release a lot of CO2?

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33% 33%33%1. Plants are burned up in

the eruption2. Crustal rocks are

melted3. The core of the Earth

contains a lot of CO2

• Most eruptions come from strato-volcanoes which erupt due to melting of crustal rocks at subduction zones.

• Crustal rocks contain CO2

Why do we have so much free oxygen in the atmosphere?

• The free oxygen (O2 – 20.9%) comes from photosynthesis.

• Analysis of ancient rocks on Earth show that the original atmosphere did not have free oxygen.

• As the oxygen level increased in the atmosphere it became possible for oxygen breathing animals to develop on the Earth.

• Before this time, only planet-like micro-organisms were possible.

Time of the Dinosaurs

Planets around other stars.

• Today we have detected over 2000 planets that orbit other stars. Most of these detections are Jupiter size gas giants because they are easier to detect.

Jupiter size planet imaged around Fomalhaut

Jupiter size

planet imaged around Fomalh

aut

Planets around other stars.

• Today we have detected over 2000 planets that orbit other stars. Most of these detections are Jupiter size gas giants because they are easier to detect.

• Currently, technology has allowed the detection of “super-earths” about 3 times the mass of the Earth.

• The data now suggests that there are literally billions of Earth-like planets in our Galaxy.

• In the next 20 years scientists will be able to analyze the atmospheric composition of nearby, earth-like planets.

• What will they search for in order to find evidence that a planet contains life?

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33% 33%33%1. Planets with water2. Planets with green

surfaces3. Planets with oxygen in

their atmospheres.

• Free oxygen in the atmospheres of planets is a key signature that photosynthesis is occurring on the planet.

• Photosynthesis means life.

• Why does Venus have the hottest surface of all the planets? (870o F)?

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33% 33%33%1. Venus is closest to the

Sun2. Venus suffers from

global warming3. Volcanic activity raised

the temperature of the planet.

Surface image from Venera 13

We can’t see infrared radiation with our eyes, but we can with infrared detectors.

• Sunlight heats up the ground. That means it makes the molecules in the ground vibrate fast when they absorb light.

• When the molecules vibrate they re-radiate the light, but not at visible wavelengths where the human eye can detect the radiation.

• They radiate at infrared wavelengths.• But it is still electromagnetic radiation (or

light).• This radiation tries to move back into space.

Greenhouse gasses

• The main molecules that can readily absorb infrared radiation are H2O, CO2, and CH4 (methane).

• Suppose it is January. The sun has been out all day and the temperature rose to 40o F.

• Just as the Sun is getting ready to set, thick clouds move in for the night.

• What will this night be like?

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1. It will get really cold because of the cloud cover

2. The temperature will only change a little because of the cloud cover

3. Don’t ask me, I’m not a weatherman.

• The temperature will not drop a lot during the night. The clouds are made of H2O which can absorb the infrared radiation and re-emit it back towards the ground.

• The water clouds serve as a blanket to hold the heat in.

• This is related to how a microwave oven works. Radiation is emitted inside the microwave with just the correct wavelength to allow water molecules to absorb the radiation. The motion of water in the food heats it up.

Venus’s atmosphere is thick and

almost completely CO2. It acts to trap in

heat.

• The temperature of Venus is in an equilibrium with the energy coming from the Sun.

• Venus does leak heat back out into space. But since the atmosphere has so much CO2 in it, it has to be extremely hot before it leaks out the same amount of energy as the Sun provides.

• Here is an example.• It’s a cold winter day. Outside the temperature is

25o F. You have the temperature set at 75o in your house. You feel too hot so you open a window in the house.

• What will happen?

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33% 33%33%1. The temperature will eventually

drop to the outside temperature2. The temperature will stay the

same because the furnace is on.3. The temperature will drop some

and then stay constant.

• The temperature will drop but it will not reach the outside temperature of 25o.

• This is because the furnace will keep producing hot air. Hot air is lost by the house, through the window, but eventually an equilibrium is reached.

• The temperature may drop to 60o but then it will stabilize and remain at this equilibrium temperature.

• With Venus the equilibrium temperature is 870o F.

• Why are scientists concerned about global warming on Earth?

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25% 25%25%25%

1. Increase in atmospheric CO2 can raise the equilibrium temperature of Earth.

2. They are paid by the government to say they are concerned.

3. They are taught it is a concern so they are biased about the dangers

4. They use complex models that can say virtually anything.

• CO2 in the Earth’s atmosphere can come from different sources, such as active volcanoes and from the combustion of fossil fuels.

• If the level of CO2 is increased then there will be a new equilibrium temperature for the Earth.

• When the temperature increases it also causes more evaporation of water which can in turn increase the amount of H2O in the atmosphere. (A greenhouse gas)

• Fortunately there is a feed back mechanism. Water clouds reflect sunlight back into space. That helps to reduce the energy reaching the planet and moderates this effect.

• Fortunately there is a feed back mechanism. Water clouds reflect sunlight back into space. That helps to reduce the energy reaching the planet and moderates this effect.

• Unfortunately, the polar ice caps are white and reflect a lot of energy back into space. When they are gone this will add to the heating of the Earth.

• Fortunately there is a feed back mechanism. Water clouds reflect sunlight back into space. That helps to reduce the energy reaching the planet and moderates this effect.

• Unfortunately, the polar ice caps are white and reflect a lot of energy back into space. When they are gone this will add to the heating of the Earth.

• Fortunately we have plants that can help to reduce the amount of CO2 by photosynthesis

• Fortunately there is a feed back mechanism. Water clouds reflect sunlight back into space. That helps to reduce the energy reaching the planet and moderates this effect.

• Unfortunately, the polar ice caps are white and reflect a lot of energy back into space. When they are gone this will add to the heating of the Earth.

• Fortunately we have plants that can help to reduce the amount of CO2 by photosynthesis

• Unfortunately we have removed most of the green vegetation on the land portion of the planet.

• Fortunately, most of the photosynthesis occurs in the oceans.

• Also the oceans are huge and can absorb CO2.• Unfortunately, the oceans are already in an

equilibrium state with the atmosphere. They can’t readily absorb more CO2.

• Also, when the globe heats up, methane is released from perma-frost adding to the heating.

• Etc. Etc. Etc…..• The “normal” state of the Earth’s atmosphere

is NOT stability.

Snow-ball Earth (2.2 billion years ago and 650 million years ago)

• Changes in the oxygen level of the atmosphere, removed methane (CH4), this reduced the greenhouse effect.

Feed-back mechanisms can tip the equilibrium in extreme ways.

• The point is there are many feed back mechanisms. Changing one variable causes changes in many variables.

• Researchers work with many different climate models, accounting for as many feed-back mechanisms as are know, and varying the conditions through millions of model iterations.

• Virtually all results show the planet will continue to warm.

• The greenhouse effect is also the reason why Mars was probably warmer in the distant past when its atmosphere was thicker.

• How is global warming like investing in the stock market?

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33% 33%33%1. It’s anybodies guess what is

going to happen2. The important thing is to

consider long term trends3. If you invest in green

technology you can make a butt load of money.

When a winter is very cold throughout the U.S. “So much for global warming” This past summer was very hot across the U.S. “Its global warming”

When a winter was very cold throughout the U.S. “So much for global warming” This past summer was very hot across the U.S. “Its global warming”

This is a long term trend. The weather in a given year is just a statistical fluctuation caused by global air currents.

Figuring out weather patterns.

• Here in Kentucky we are moving about 700 MPH, due to the Earth’s rotation on its axis.

• Which direction is the Earth turning?

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25% 25%25%25%1. It is turning East2. It is turning West3. It is turning North4. It is turning South

Image a trip from Lexington to Rome, Italy and back. Assume no wind on the trip.

• How does the Earth’s rotation affect this trip?

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33% 33%33%1. The trip to Rome is

shorter than the trip back to Lexington.

2. The trip back from Rome is shorter than the trip to Rome.

3. No affect

• It has no affect.• The plane flight is the same both ways.• The plane before take-off is already moving

700 MPH, due to the Earth’s rotation. When it is flying it is traveling around 500 MPH relative to the ground plus the 700 MPH it had at take off. Same thing for the return trip.

• Ancient Greeks used this kind of idea to say that the Earth was NOT rotating.

• What happens when you jump in the air?• If you are in the air for one second, here in

Kentucky, the Earth would rotate underneath you at 700 MPH.

• For one second you would land 300 meters to the west. That’s 3 football fields.

You land in the same spot.

700 MPH

700 MPH

700 MPH

You land in the same spot.

700 MPH

700 MPH

700 MPH

You land in the same spot.

700 MPH

700 MPH

700 MPH

Canada launches an attack on the Panama Canal by firing a cannon ball. They aim directly at

Panama.

• Where will the cannonball land?

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33% 33%33%1. It should hit the target.2. It will hit West of the

target3. It will hit East of the

target.