Wednesday, February 15, 2006

Earth’s Bright and Angry Sister

Earth’s Bright and Angry Sister
by Dave Adalian

That bright light shining in the east during early morning hours this spring isn’t a UFO, and it’s not an airplane coming in to land, either.

It’s Earth’s sister planet, Venus.

Of the four inner rocky planets of our Solar System, Venus is the most like our home--but there’s a world of difference, too.

Venus is almost exactly the same size as Earth, just over 400 miles slimmer at the equator, and boasts 80 percent of our planet’s mass. Venus and Earth (and Mercury and Mars, too) are also made of pretty much the same stuff, unlike the outer gaseous planets, and at one time Venus had its own water.

This is where the similarity stops.

Venus is about one third closer to the Sun on average than Earth, and solar heating caused by this proximity kept the water on Venus from becoming a liquid. Having an atmosphere comprised of mostly water vapor led to an extreme greenhouse effect, with the trapped heat eventually destroying Venus’s water and driving huge amounts carbon dioxide from the surface rock, pushing the heat even hotter.

Today, temperatures on Venus range from lows in the 260-degree range with highs approaching 900, and the atmospheric pressure is 90 times that of Earth at sea level. These conditions are widely, famously and rightly reported as being hot and nasty enough to melt lead.

Adding to Venus’s oddness is its retrograde rotation. While the other planets turn counterclockwise as seen from above their north poles, Venus rotates clockwise, meaning on Venus the Sun rises in the west. But, you’d have to wait a long while to see it.

Venus, because it is closer to the Sun, has a year that is only 225 Earth days long, but it takes 243 days to turn on its axis. On Venus, a day is longer than a year.

As 2005 ended, Venus put on a months-long display as the spectacular Evening Star, dazzling in the west during the hours after sunset.

Now, she’s back, only this time in her incarnation as the Morning Star, shining her brightest for 2006 tomorrow during the hours before dawn when early risers will find her hanging jewel-like in the predawn eastern sky.

This apparition will last into May, when we should be hearing much more about Venus and its bright atmosphere as the European Space Agency’s Venus Express probe reaches our sister planet and begins returning data on the makeup of its stifling conditions.


This column appeared originally on Feb. 16, 2006 in the Visalia Times-Delta.

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