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Atmosphere of Venus Mars and Earth
Atmosphere of Venus, Mars and Earth
Yoshihide Kozai
os
de o a
2009 Asian Science Camp
August 3
The Earth from the Moon
The Earth from the Moon
Venus
Mars
Jupiter
• Orion Nebula
Where stars are born
Where stars are born
Distance 1500light Years 50 light year Wide(3 million AU)
(
)
Stars are born where
D it f i t t ll
Density of interstellar
Matter is high.
Chemical Composition of Atmosphere
Chemical Composition of Atmosphere
•
•
•
•
•
•
Chemical composition of atmosphere(%)
Ch
i l
iti
f t
h (%)
N2 O2 CO2
H2O Venus 3.4
34
0 007
0.007 96
0 019
0.019 Earth 78
21
0.037 1~2.8
Mars
2.7 0.13
95
0.03
Jupiter •
Surface pressure Temperature
• Venus 90 atm.
460˚C
• Earth E th
1
20˚C
• Mars 0.006
‐60˚C
H2 He
89
11
Solar distance
0.72 AU
1 00
1.00
1.52
Greenhouse Effect
Greenhouse Effect
High temperature of Venus is caused by g
greenhouse effect due to thick atmosphere.
p
When the sky is very clear (without clouds and greenhouse gases) the temperature comes
greenhouse gases), the temperature comes down because of no blanket against infrared radiation from the surface.
f
h
f
Carbon dioxide makes a greenhouse and if its
Carbon dioxide makes a greenhouse and if its abundance is much lower, the mean temperature of the earth should be lower
temperature of the earth should be lower.
Greenhouse effect
SUN
Infrared radiation is
absorbed/scattered in the atmosphere.
p
Cloud
CO2
Infrared Light
g
CO2
H2 O
Cloud
l d
CO2
H2 O
Vi ibl
Visible
Light
Surface
Mars Earth
Mars Earth Venus
Venus
Comparison of the Atmospheres
Comparison of the Atmospheres
• Venus
–
–
460 ˚C >> 50˚C (no greenhouse)
( g
)
Water unstable • Mars
M
–
–
Thick CO2 Strong Greenhouse
V thi CO2 Very weak Greenhous
Very thin CO
V
kG
h
‐ 60˚C
Water frozen
• Earth N2‐O2 little CO
little CO2 Moderate Moderate
Greenhouse
–
–
20˚C > 5˚C (no greenhouse)
Water stable = Ocean
Evolution of the atmosphere:
Evolution
of the atmosphere:
How the Earth decreased CO2 ?
• Carbon dioxide (CO2) was first absorbed by huge sea covering the earth
sea covering the earth.
• In the sea, several plants were born and by their photosynthesis effect the plants absorbed carbon dioxide and made oxygen (O
ca
bo d o de a d ade o yge (O2)) .
Photosynthesis
Organic matters
Stromatolite
Modern stromatolites in Shark Bay, Western Australia
Stromatolites are layered accretionary structures formed in shallow water by
the trapping, binding and cementation of sedimentary grains by biofilms of
microorganisms,
i
i
especially
i ll cyanobacteria
b t i ((commonly
l kknown as bl
blue-green
algae). They include some of the most ancient records of life on Earth.
Fossile Stromatolite
Fossile Stromatolite
Microfossils 3.5x109 yr before present
(Australia) that resemble filamentous
cyanobacteria
Increase in oxygen
Increase in oxygen
• In
In the sea, chlorophyta produced oxygen by the sea chlorophyta produced oxygen by
photosynthesis and oxygen amount increased to be 1/100 of the present Then multicellular organism
1/100 of the present. Then, multicellular organism appeared on the Earth. It was 800 million years ago that crustacean and mollusk appeared when oxygen
that crustacean and mollusk appeared, when oxygen amount was 1/10 of the present. Accordingly ozone (from three oxygen atoms) started increasing and the
(from three oxygen atoms) started increasing and the ozone layer in the upper atmosphere stopped solar UV and X ray which are poisonous for the life
UV and X‐ray, which are poisonous for the life. Formation of the ozone layer promote the life on the land.
land
Chlorophyta
multicellular organism
crustacean
mollusk
Global Warming
Global Warming
Organic materials containing carbon produced by photosynthesis were stored underground; oil was produced from organic materials. Coral reefs formation in the ocean capture carbon dioxide. (Limestone is composed of fossils of coral.) In recent 300 years as industrial activity has been very active by using oil and coral. Then much carbon dioxide was again produced.
In the recent 50 years or so, global warming has become a serious problem.
p
Oil Field
Coral Reef
Global Warming
Global Warming
• Increase in carbon dioxide in the atmosphere enhanced the greenhouse effect that delays the escape of energy obtained from solar radiation. That results in the global temperature increase, i.e., global warming.
• Melting of glaciers by the global warming should raise the sea level, which would be fatal for low‐
elevation islands.
• Japan is now in “temperature” zone. As proceeds the global warming, Japan will enter “subtropical” g
g, p
p
zone with hotter and more humid climate.
Light pollution
Light pollution • Astronomical observation is strongly affected by g p
“light pollution”, excessive obtrusive artificial lights. Especially in and around the large city, artificial lights brighten the night sky and
artificial lights brighten the night sky and prevent star observation. Under the sky glow of artificial lights which affect long exposure
of artificial lights which affect long‐exposure photographing, it is very difficult to observe dark stars. From the beginning of 20th century, astronomical observatories moved from cities to remote places with dark sky.
Dark sky
Light
pollution
• Looking down the night earth from the space, we realize too much light have escaped to the sky. This amount is much greater than the least g
necessary illumination for lands. • Light Environment Ordinance
(Outdoor Lighting Ordinance)
In order to decrease light pollution, Bisei‐town, g p
,
,
Takayama‐village, Hamamatsu‐city, Tucson‐city (US) enacted “Light
(US) enacted Light Environment Ordinance
Environment Ordinance”.. For For
example, streetlights should be covered not to emit light upward to the sky This would also
emit light upward to the sky. This would also decrease the power consumption.
Earth at night from a Satellite
Earth at night from a Satellite
Habitable planet (habitable zone)
Habitable planet (habitable zone)
Li id water
Liquid
t iis stable
t bl on th
the surface
f
off a planet.
l
t
Factors controlling “habitability”
Factors controlling habitability
• Distance from the sun (main star).
• Atmosphere (Greenhouse effect).
Atmosphere (Greenhouse effect).
• Gravity
– Too small planets do not have atmosphere.
• Composition (presence of water).
Composition (presence of water).
• Luminosity of the sun (main star).
Mars was habitable
Mars was habitable.
River delta
Sedimentary rocks
Why was Mars habitable ?
Why was Mars habitable ?
• Thick CO2 atmosphere 4.0 billion yr ago.
• (3
(3‐5
5 atm. P
atm. PCO2)
• Strong greenhouse effect.
• Thick atmosphere Thick atmosphere ‐‐ escaped ?
escaped ?