VENUS – RUNAWAY GREENHOUSE
Venus’ atmosphere is dense (90 times Earth’s) and composed mostly of CO2 (carbon dioxide).
Thick clouds of sulfuric acid obscure the surface.
The atmosphere produces a run-away greenhouse effect that raises Venus’ surface temperature to over 450 degrees C (hot enough to melt lead). Venus’ surface is hotter than Mercury’s despite being nearly twice as far from the Sun.
Venus probably once had lots of water like Earth that boiled away, leaving it quite dry.
Earth might be like this if it were a little closer to the Sun.
Not yet clear why Venus turned out so differently from Earth