Q. Why is our atmosphere so different from that of Venus, which is 90 times thicker than ours?

Rockport High School

A. In one way, carbon dioxide-breathing plants would be very happy on Venus. The atmosphere there is 96 percent CO2. Compare that with our atmosphere, which is a third of 1 percent CO2.

Of course, all that carbon dioxide creates other conditions on Venus, the second planet from the sun, that plants would not be happy about. Like a surface temperature of 860 degrees Fahrenheit, caused by the greenhouse effect of carbon dioxide; it traps solar radiation before it can bounce off the planet's surface and back out into space. In fact, though Venus is twice as far from the sun as Mercury, its surface is much hotter. Don't put lead in a spaceship to Venus. It would melt!

The different composition of the Venusian atmosphere creates a surface pressure 90 times greater than sea level air pressure on Earth. Standing on the surface there would be equivalent to being about 3,000 feet down in the ocean here.

Earth and Venus are made of the same basic minerals, they're close in size and mass, and are thought to have similar seismic, volcanic and tectonic activity. The reason the atmosheres are so different is, in a word, life. On Earth, biological processes gobble up carbon dioxide as it erodes out of minerals and enters the atmosphere. The ocean's plants are a huge `sink' for CO2, for example. So are terrestrial flora. But on Venus, when CO2 goes up, it stays up.