The Curiosity Lander is now roaming the surface of Mars, looking for evidence of life—past or present—on the red planet. Curiosity is a marvel of NASA’s engineering capabilities. It cost a lot of taxpayer dollars, but it embodies the human spirit to explore unknown lands.
I suspect evidence of life on Mars will be disappointing. But, I am all in favor of exploring nearby planets to gain a better understanding of our own home.
Earth’s atmosphere is about 78% nitrogen and 21% oxygen. Small amounts of water vapor and carbon dioxide keep Earth’s temperature about 50 degrees Fahrenheit warmer than it would otherwise be given its distance from the Sun. This allows for liquid water on Earth.
Mars is farther from the Sun, so one might logically expect it to be colder than the Earth. It has a very thin atmosphere, with a little bit of carbon dioxide and essentially no water vapor. Mars does not experience the greenhouse effect that carbon dioxide confers on Earth. It is a cold place – about 54 degrees Fahrenheit below zero on the surface.
Venus is closer to the Sun, and thus, you might expect it to be warmer than the Earth. And it is. But the surface temperature on Venus – about 885 degrees Fahrenheit – is much hotter than predicted based on its orbit. Venus’ atmosphere is about 100x thicker than Earth’s, and nearly all composed of carbon dioxide.
Next time someone tells you that greenhouse warming of our planet is a hoax, ask them about Venus. More than one atmospheric scientist has said, “God put Venus in the heavens to show us what a planet with lots of atmospheric carbon dioxide might look like.”
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Photo, taken on October 8, 2010, courtesy of U.S. Department of Agriculture via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.