Earth History

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The ability of molecules to remain in the atmosphere is also related to the mass of the earth.

The escape Velocity Ve = (2Gm/R)1/2

m = Mass, G=Universal Gravitational Constant, R = Radius

Slide 27

Escape Velocity

Escape Velocity (Ve)

Ve = (2Gm/R)1/2

m = Mass of the Planet

G= Universal Gravitational Constant,

R = Radius of the Planet

Escape Velocities in km/s

Earth = 11.2 Venus = 10.3 Mars = 5.0

Slide 28

Escape Velocity

The ability of molecules to remain in an atmosphere is related to the mass.

Density Diameter Distance from Sun

Mars 3.94g/ml 6794km 227.9 Mkm

Earth 5.52g/ml 12756km 149.6 Mkm

The Molecule’s Escape Velocity and nature of the molecules determines the composition of the atmosphere.

Slide 29

No H or He in Earth’s Atmosphere

At 600 K (Upper Atmosphere )

For H atoms 1 in 106 exceeds the escape velocity.This is High enough for rapid depletion of H from the atmosphere

As a result all the Hydrogen on earth is present in a bound state.

(Water, Organic material)

Slide 30

Little CO2 in atmosphere

For Oxygen only 1 in 1084 atoms exceeds the escape velocity .This indicates negligible depletion of Oxygen.

Presence of Life on Earth has removed Carbon dioxide from the Atmosphere and given rise to oxygen. Shellfish/Coral.

( Calcium Carbonate and Plant Material )

Slide 31

Earth ,Venus & Mars

Surface Characteristics of Planets

Temperature Pressure (bar)*

Venus 732 K (459oC) 90

Earth 288 K ( 15oC ) 1 (101325Pa)

Mars 223 K (-55oC ) 0.006

*1 bar = 100,000Pa

= 10m in depth of the Ocean

Slide 32

Distribution of Gases on Earth Venus & Mars

Composition of Planet’s Atmospheres in %

CO2 N2 O2 SO2 H2O

Venus 96.5 3.5 0.015

Earth 0.03 78.1 20.9 (varies)

Mars 95.3 2.7 < 0.1 0.03

Slide 33

Role of Shellfish

Presence of Life on Earth has removed Carbon dioxide from the Atmosphere and given rise to oxygen.

Shellfish/Coral. in the Sea,Air,Land Interface has immobilized Carbon dioxide as Calcium Carbonate while Photosynthesis has given rise to oxygen and Plant Material

Slide 34

Triple point of H2O

P(H2O) in Atmospheres