Moon and Venus

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Several hundred million years ago, the planet Venus may have turned itself inside out. Millions of cubic miles of molten rock bubbled to the surface, repaving almost the entire planet with smooth volcanic plains.

Today, this landscape is showing its age. Thousands of volcanoes rise from the plains, big domes of volcanic rock punch up through the crust, and deep cracks slice through the surface.

The landscape tells us that Venus is probably put together a little differently than its "sister planet," Earth. On Earth, "plates" of lightweight rock float across the denser rock below, forming our planet's crust. Mountains and volcanoes are born where the plates ram together, while new crust forms where they pull apart.

But Venus's crust probably consists of a single plate that enwraps the entire planet. Molten rock occasionally punches through thin spots in this cap to form volcanoes and related features.

We don't know if any of the volcanoes are still active, though. There's evidence that a few may still belch gases and thick lava, but it's hard to watch the surface through the planet's unbroken cloud cover. A European orbiter is peeking through the clouds even now, searching for volcanoes rumbling atop the volcanic plains.

Look for Venus to the upper left of the Moon this evening. It's the brilliant "evening star." It's in the southwest at sunset, and sets in mid evening.

More about Venus and the Moon tomorrow.

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.