EARTHSS 23 Lecture 2: ESS23 Lecture 2
10 Mar 2017
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Document Summary
Sun and earth formation 4. 6 billion years ago. Nuclear fusion (star"s): hydrogen into helium and higher elements releases energy (photons) and ultimately releases stellar material back into space. Solar radiation: shorter wavelength = higher energy, peak wavelength = 2897/t (wien"s displacement law) black body radiation . Temperature of sun (photosphere): 5800 k, 20 times higher than earth, so peak wavelength for sun to earth is 20 times lower. Earth"s first atmosphere: consisted mostly of h, he (most abundant elements in the solar nebula) During birth of sun, nuclear reactions were enhanced, increasing solar wind and stripped off most h and he from the earth"s atmosphere, h and he can be lost by escaping from the earth"s gravitational field. Earth"s second atmosphere: gaseous materials from outside earth, 4 bya due to outgassing by volcanoes, fumaroles, steam wells, geysers, hydroxyl molecules (oh) bound in crustal minerals, became detached and converted reduced gases to oxidized gases.
