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Moon and Jupiter

October 12, 2011

One of the most exotic bodies in the solar system is Io, one of the large moons of Jupiter. It’s covered by hundreds of volcanoes — more than any other planet or moon in the solar system. Their molten rock and volcanic gases color Io in shades of yellow, orange, white, and brown.

Io is such an active world because of a gravitational tug-of-war between Jupiter and some of its other large moons.

The same side of Io always faces Jupiter, just as the same side of our moon always faces Earth. But as Jupiter’s other moons move past Io, they pull at it, trying to turn it around. That creates tides in Io’s crust. While the largest tides in Earth’s oceans are only about 60 or 70 feet high, the tides in Io’s solid surface are more than 300 feet high. All of that energy melts the rock in Io’s interior, which pushes its way to the surface.

At the surface, the molten rock bubbles up through craters or cracks in the crust, sometimes building broad volcanic mountains. Much of the rock spreads out to form wide plains.

Some of the volcanoes produce giant plumes of ash and gas, including the most prominent volcano of them all, known as Pele. We’ll have more about that tomorrow.

In the meantime, look for Jupiter rising to the lower left of our own Moon early this evening, and following the Moon during the night. It looks like a brilliant star. Through binoculars, Io and three other moons look like tiny stars arrayed near the giant planet.


Script by Damond Benningfield, Copyright 2011


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