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The atmosphere of our Earth, of planets of our solar system andof exoplanets

Author(s): Brüesch, Peter

Publication Date: 2016

Permanent Link: https://doi.org/10.3929/ethz-a-010580544

Rights / License: In Copyright - Non-Commercial Use Permitted

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1. P r o l o g u e

The Atmosphere and the

Air of our Planet

1

1 – 1

The Atmosphere in its primitive state

2

Our Earth has been formed about 4.5 Milliards of years ago. Already the early Earth

had an Atmosphere consisting of (H2) and Helium (He), as well as on small

concentrations of Methane (CH4), Ammonia (NH3) and of some Rare Gases (the

Figure shows only H2 and He). Because of the small gravitational force and due to

the fast rotation of the Earth, these molecules have been attracted only weakly to the

Earth and many molecules have been lost into Space. The loss of the early Atmosphere

was also due to the heat producing gravitational contraction of the Earth, the decay of

heat-creating radio-nucleids as well as to the impacts of Meteorites and Asteorides.

Because of the high temperature which has further been increased by nuclear fusion in

the Sun, as well as due to the extremely intense solar winds, the last remnants of the

atmosphere have been removed.

1.1 Formation of the Earth’s Atmosphere

Atmosphere of the young Earth

3

The young Earth: Water vapor (H2O), Carbon dioxide (CO2) and Ammonia (NH3) has

been released by active volcanoes. CO2 was dissolved in sea water. Simple bacteria

have been created with the help of sunlight and CO2. and as a byproduct, molecular

oxygen (O2) was formed.

This second Atmosphere originated from the Earth itself. At that time, a very large

number of volcaneous existed, much more than in the present time. This volcanism

was a consequence of the formation of a crust of the Earth. From the volcaneous, the

following gases have been ejected:

a) Water vapor (H2O - molecules)

b) Carbon dioxide (CO2) dissoved in sea water

c) Ammonia (NH3) from the volcaneous into the Atmosphere

1 – 2

Present Atmosphere of the Earth

4

Present Earth: Plants and animals developed together in equilibrium. Plants are

breathing carbon dioxide (CO2) and exhale oxygen (O2) (see Photosynthesis, Chapterl 6).

In the Oceans, al large quantity of CO2 is dissolved. During a large period of time, simple

bacteria have been developed. These bacteria are living from CO2 and sunlight. As a

byproduct, these bacteria generated oxygen (O2). This led to an enrichement of O2 and a

corresponding decrease of the CO2 concentration in the Atmosphere. At the same time,

Ammonia (NH3) was decomposed by sunlight, whereby molecular nitrogen (N2) and

molecular hyddrgen (H2) has been formed. The light H2 – molecules ascended to the

highest layers of our atmosphere and eventually diffused out into the free space of the

Universe.

5

1.2 Atmosphere and Air

Atmosphere

The Atmosphere of the Earth is a gaseous layer which surrounds our Planet. These

gases are attracted by the gravitational force of the Earth. The Atmosphere protects

life on our Planet by absorbing the UV- radiation of the Sun, by protecting the Earth’s

surface from overheating (natural Greenhouse effct), and by reducing extreme

temperature changes between days and nights.

The Atmosphere has different layers which can be distinguished by their different

temperatures and compositions. The Atmosphere has a mass of about 5.15 x 1018 kg,

and about three quarters of this mass is present within the first 11 km from the

surface of the Earth (p. 10). With increasing altitude, the density of the Atmosphere

decreases continuously (p. 1-A-3-1) but there is no definite boundary between the

Atmosphere and outer space. The Kàrmán line, at 100 km, is often regarded as the

boundary between Atmosphere and outer space.

Air

Air is the name given to the Atmosphere used in breathing and photosynthesis. Dry air

contains roughly (by volume) 78.09 % nitrogen, 20.95 % oxygen, 0.93 % argon, 0.039 %

carbon dioxide, and small amounts of other gases (s. p. 6). Natural air also contains a

variable amount of water vapor, on average around 1 %.

While the air content and atmospheric pressure vary at different layers, air suitable for

the survival of terrestrial plants and terrestrial animals is currently only known to be

found in Earth’s Troposphere (pp 7,9,10). In addition, air can also produced in artificial

atmospheres.

1 – 3

Composition of the dry (water-free) Atmosphere

[in Vol. % and in parts per million (ppm)]

Carbon dioxide:

CO2

Argon : Ar N2 : 78.084 %

(780 840 ppm)

O2 : 20.946 %

(209 460 ppm)

Ar : 0.934 %

(9 340 ppm)

CO2 : 0.036 %

(360 ppm)

Residual gases:

Methane (CH4) : 1.5 ppm

Nitrogen-oxide (Laughing gas): N2O

Nobel gases, H2

Residual

gases

Oxygen: O2

Nitrogen: N2

6

(Composition of the Troposphere: s. p. 16)

Layers of the Atmosphere

7

Spectacular view of Earth’s Atmosphere

The 6 layers of the Atmosphere

A brilliant sequence of colors in the image de-

notes each of the layers of Earth’s Atmosphere,

which are visible here because the picture was

taken why the «International Space Station» had

an edge-on view (Kantenansicht), or limb, view on

the Earth. From this vantage point (Blickwinkel),

the Earth’s curvature can also be made out.

Stratosphere

Tropospherelimb

upper atmosphere

1 – 4

All the Air on Earth:Sphere with a radius of R ≈ 1000 km

At techn. Normal Conditions:

(20 oC, 1 atm) this corresponds

to a mass of about 5.2 * 1018 kg.

At normal pressure, the height of the

total Atmosphere would only be 7.8 km.

The Air layer is very thin:

Troposphere + Stratosphere

together: only about 50 km

8

All the Air on Earth

No liquid water on our Planet:

only Ice !

Without the air layer, the global

temperature would be

about – 15 to – 18 0C !

Air layer = protection layer:

stores the heat radiated from

the Earth in the Infrared.

Pullover effect !

1.3 The Layers of our Atmosphere

9

10’000 km

690 km

85 km

50 km

20 km

Mesopause- boundary: Mesosphere /Thermosphere

Mesosphere - burn out of most meteos

Troposphere – the layer closest to the Earth’s surface:

contains almost all of the air - wheather zone

Tropopause – boundary: Troposphere /Stratosphere

Stratosphere - contains the ozone layer

Stratopause – boundary: Stratosphere / Mesosphere

Thermosphere – extremely small concentration of molecules

Thermopause – boundary: Thermosphere/Exosphere

Exosphere – outermost layer of the atmosphere

1 – 5

R = 6’357

km

- Troposphere: 0 to

about 11 km altitude;

- Stratosphere: 11 to

about 50 km altitude;

- Mesosphere

Very thin protective layer !

Contains more than 99 % of

the mass of terrestrial

Atmosphere.

Atmosphere of Earth:

Thicknness about 50 km

In this case, liquid water would not exist on Earth !

Earth

10

Protective layer stores

the heat radiated from the

Earth – Radiation in the

Infrared Pullover !

Without protective layer,

the global temperature

would be – 15 to – 18 0C

1.4 Atmospheres of other Planets

11

While Chapters 1 to 9 are dedicated to the Atmosphere of our Earth, Chapter 10 will

contain a discussion of the Atmospheres of Planets of our Solar System as well as of

Atmospheres of Exoplanets, i.e. of Planets outside our Solar System.

The Universe contains approximately 100 to 200 billions of Galaxies, and each

Galaxy, such as our Milky Way Galaxy, contains again 100 to 200 billions of Stars and

many of these Stars are orbited by many Planets.

The structure and Atmospheres of the Planets of our solar system are known to a

great extent. Therefore, today and in future, Exoplanets in our Milky-Way Galaxy are

studied extensively. The studies are dedicated to the search of Earth-like Planets in

which life or even intelligent live exists. In other words: Scientists are trying to find a

«Second Earth».

Our solar system The Milky-Way Galaxy

1 – 6

A-1-0

Appendix – Chapter 1

1-A-3-1

Druck , relative Dichte und Temperatur

in Abhängigkeit der Höhe

11

Hö

he h

(k

m)

Druck p (mb)

R

relative

Dichte Man beachte den komplexen

Temperaturverlauf in Abhängigkeit

der Höhe h !

Temperature (0C)

Hö

he h

(k

m)

h(p) nach barometrischer Höhenformel

Pressure, relative Density and Temperature

as a function of altitude

Alt

itu

de

h (k

m)

Pressure p (mbar)

relative

density

Hh(p) according to barometric height

formula

Note the complex temperature

variation as a function of altitude

Temperature (0C)

Alt

itu

de

h (k

m)

1 – 7

R-1-0

References: Chapter 1

R-1-1

References : Prologue

1.1 Formation of Earth’s Atmosphere,

Asteorides, Meteorites, Comets - Solar Wind

R.1.1.1 p. 2: [PDF] TODAY – Asteroids, Meteorites, Comets …

www.astro.umd.edu/~miller/ASTR100/class13.pdf

R.1.1.2 p. 2: ASZEROID WATCH

Asteroids, Comets, Meteorites

http://www.jpl.nasa.gov/asteroidswatch/asteroids_comets.cfm

R.1.1.3 p. 2: Was ist der Unterschied zwischen einem Asteroiden , Kometen und Meteoriten ?

http://www.astronews.com/frage&antworten/1frage1783.html

R.1.1.4 p. 2: The Solar Wind

http://solarscience.msfc.nasa.gov/SolarWind.shtml

R.1.1.5 p. 2: Sonnenwind

www.http://de.wikipedia.org.wiki/Sonnenlicht

R.1.1.6 pp 2 – 4: How did the Earth’s Atmosphere form ?

http://scijinks.nasa.gov/atmosphere-formation

R.1.1.7 pp. 2 – 4: Erdatmosphäre

http://www.reinis-welten,de/weltgeschichte.dieerde/erdatmosphaere/index.html

R.1.1.8 pp 2 – 4: History of the Earth

http://en.wikipedia.org/wiki/Histoty_of_the_Earth

1 - 8

R-1-2

R.1.2.3 p. 7: Levels of the Atmosphere

a) Left hand picture: ISS crew captures spectacular view of Earth’s Atmosphere

http://www.instantfundas.com/2010/06/iss-crew.captures-spectacular-view-of.html

b) Right hand picture Layers of the Earth’s Atmosphere

http://www.buzzle.com/articless/layers-of-the-earths-atmosphere.html

R.1.2.4 p. 8: All the Air on the Earth

a) All the water and air on earth gathering into spheres and compared to the Earth

http://boingboing.net/2008/03/11/all.the-water-and_air.htm

b) Next Nature

http://www.nextnature.net/2008/03/all-the-water-and-air-on-eaeth/

c) Wasser und Luft der Erde : Alle Luft der Erde

Adam Nieman:

http://www.adamniemann,co,uk/vos/index.htnl

1.2 Atmosphere and Air

R.1.2.1 p. 5: Atmosphere of Earth

www.http://en.wikipedia.org/wiki/Atmosphere_of_Earth

R.1.2.2 p. 6 : «Origin of the Earth’s Atmosphere»

http://www.ux1.eiu/cfjps/1400/atmos_origin.html

Figure textsL P . Brüesch

R-1-3

R.1.3.1 p. 9: Layers of the Atmosphere

http://ete.cet.edu/edu/?/volcanoes/layers/

R.1.3.2 p. 10: Comparision of Air-layer thickness with Earth’s Radius

Figure and Text from P. Brüesch with information from different Literature sources

R.1.4.1 p. 11: Atmosphären des Sonnensystems und Exoplaneten

a) Planetary system

http://en.wikipedia.otg/wiki/PPlanetary_system

Left hand picture: Our solar system

b) Solar System

http://en.wikipeia/org/wik/Soalr:System

c) Sonnensystem

http://de.wikipedia/wiki/Sonnensystem

R.1.4.2 a) Milky-Way

http://en/wikipedia.org/wiki/Mylky_Way

b) Right hand picture: The Milky-Way Galaxy

in: http://www-simone-bahia.de/astronomie/milchsreasse.html

Appendix

1.A.3.1 Pressure, Composition and Temperature of Earth^s Atmosphere

Earth’s Atmosphere_ Composition and Structure

- www.visionlearning.com/.../library/Earth-Science/

[contains all 3 Figures: Pressure p(h) / relative Density r(h) and Temperature T(h)]

Left hand Figure: p(h) corresponding to simple narometric height formula, (strongly idealized)

Right hand Figure: p(h) corresponds to realixtic pressure variation

- Pressure and density of the Atmosphere as a function of altitude

s. p. 54, Chapter 2

1.3 The Layers of our Atmosphere

1.4 Atmospheres of other Planets

1 - 9

1 – 9