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Making Venuses

April 3, 2012

The hottest real estate in the solar system is on Venus, the second planet out from the Sun. Surface temperatures are around 850 degrees Fahrenheit -- hotter even than Mercury, the closest planet to the Sun.

Venus is kept hot by its atmosphere. It caused a “runaway greenhouse,” which boiled off any water on the surface and created a planet-wide hothouse.

But there may be another way to make a planet as hot as Venus is: tides.

Here on Earth, ocean tides are caused by the gravitational pull of the Moon and Sun. The side of Earth that’s closest to these bodies feels a slightly stronger gravitational pull than the side that’s facing away from them. This difference creates a “bulge” in the oceans that moves around Earth, creating the tides.

This process also creates tides in the solid Earth. But they’re so small that we don’t notice them.

But if a planet orbits close to a fairly small parent star, the difference in the gravitational pull on the two sides of the planet would be immense. That would create huge tides throughout the planet, heating its interior. Research by Rory Barnes of the University of Washington and his colleagues suggests the tides could be strong enough to heat the planet’s surface to hundreds of degrees -- creating a hellish world just like Venus.

Look for Venus itself well up in the west as night falls this month, shining as the brilliant “evening star.”

More about planets in other star systems tomorrow.


Script by Damond Benningfield, Copyright 2012


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