The surface temperature of Venus reaches some 900F. Added to that is an atmospheric pressure about 90 times Earths: High overhead in the carbon dioxide (CO2) that passes for air is a layer of clouds, perhaps 10 to 20 miles thick, whose little drops consist mostly of sulfuric acid (H2SO4). Water is all but nonexistent.
Born with so many fundamental similarities to earth, how did Venus get to be so radically different: It is not just an academic matter. For all its extremes, Venus is a valuable laboratory for researchers studying the weather and climate of earth. It has no earths oceans, so the heat transport and other mechanisms are greatly simplified. In addition, the planet Venus takes 243 earth-days to turn once on its axis, so incoming heat from the sun is added and distributed at a more leisurely, observable pace.
16. Venus is similar to Earth in ________.
[A] size and density
[B] distance from the sun
[C] having atmosphere
[D] all of the above
17. The greatest value in studying Venus should be to ________.
[A] allow us to visit there
[B] understand Earth better
[C] find a new source of energy
[D] promote a new space program
18. The main idea of this passage is about ________.
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