Flashcards
Origin of atmosphere (12)
Flashcards do conjunto (15)
- 1What is the origin of Earth's atmospheric gases?Volcanic out gassing during & after the iron catastrophe
- 2☼What is modern air composed of?☼☼78% N sub2
☼21% O sub2
0.9% Ar
0.04% CO sub2 - 3What is the composition of early air?H2O, CO2, SO2, CO, N2, H2, H2S, HCl + secondary CH4, NH3
- 4Did the earliest air have free oxygen (O2)?Early air was anoxic - No free oxygen (No O2)
- 5How did early air change through time?-Slow chemical & biologic changes
-Buildup of CH4 (methane), then a fall
-Buildup of O2 by photosynthesis and photochemical dissocation.
-H2 lost to space; decrease in out gassing through time. - 6How did the levels of free oxygen build up in Earth's atmosphere?Photosynthesis (microbes) and photochemical dissociation (sunlight splits apart gas molecules)
(~3.46 Ga) - 7☼Explain cometary source of oceans☼-comets (dirty snowballs) melt upon impact to Earth.
Problem: D/H ratios of Earth's seawater and many comets don't match.
☼Some comets do have the chemistry of our sea water☼ - 8Explain the volcanic outgassing-cooling-condensation-(Ocean water has some origin as atmosphere)
-Volcanoes -> Gases -> #1 gas = H2O as very hot gas -> cooling -> skys rained out - 9Explain grazing impact of water-rich asteroidsAsteroids that flew by earth transferred water to earth
-D/H relationship is similar
-Rare today, but not early sol. system - 10How and why did the (apparently) biggest and hottest rain event ever occur?? Due to volcanic outgassing ? (No Notes)
- 11When did Earth first have oceans?At least 4.4 Ga based on mineral evidence from Australia.
- 12☼What was the earliest ocean water like?☼Probably acidic (low PH)
- 13Why were the earliest oceans likely acidic?Because of high levels of CO2
- 14Did limestones form in the earliest oceans?Nope
- 15When did the Earth’s early oceans first have significant populations of microbes?Present by 3.2 Ga