What is the majority of the earths atmosphere?

Questions on Earths and Venus's Atmosphere.?

• I have some questions on earth and venus's atmosphere. 1. Where is venus's water now? The earths? 2. Why does venus have so much CO2 in its atmosphere? 3. Why is venus enshrouded in clouds while earth isn't? 4. Where is venus's n2? 5. How did the earth get its O2? 6. Why is Venus's runaway greenhouse relevant to earth today? Thanks Guys!

• Answer:

  1. Planetary scientists think that the planet has lost part of its water in this way over the four-and-a-half-thousand million years since the planet’s birth. 2. The conditions on Venus are a good example of the "greenhouse effect" which explains why although Earth and Venus have roughly the same amounts of CO2, on the Earth this mainly locked into the rocks, but on Venus it has been freed by the temperature, pressure of the atmosphere (90 times that of the Earth) and the greenhouse effect. 3. Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. 4. Venus's Nitrogen Gas is still in the atmosphere. 5. Atmospheric oxygen is a result of photosynthesis by plants (including cyanobacteria - blue-green algae - which was responsible for the initial conversion of earth's atmosphere from its anoxic state). Photosynthesis is carried out in plants. It employs energy from the sun and naturally occurring water and carbon dioxide to produce sugar and oxygen gas. The oxygen is released to the atmosphere, and the sugar is formed into plant matter, which eventually dies and is buried and turned into coal and oil and gas. 6. Because of how Venus and Earth are almost exactly the same in size.