The Moon and the planets Venus, Mars, and Saturn put on quite a show this evening. The planets align to the of right the Moon. They're fairly low in the sky at sunset, and they all drop from view by a couple of hours after sunset.
Venus is the brightest of the three planets. It shines so brilliantly in part because clouds blanket its surface. The clouds never part, so we can't see the surface directly.
But a spacecraft that entered orbit around Venus 20 years ago this week managed to map almost the entire planet.
Magellan accomplished that task with radar, which penetrated the clouds. The radar echoes provided a detailed view of the planet's contours, revealing continent-sized plateaus and giant volcanoes and canyons.
The observations showed that the entire surface is made of volcanic rock. In fact, they indicated that hundreds of millions of years ago, giant eruptions completely repaved the surface. They also hinted that some volcanoes might still be active, although Magellan didn't catch any of them actually erupting.
A couple of other missions also used radar to study Venus, but they didn't map the surface with anywhere near the same level of detail. And a few probes have touched down on Venus, but they survived for only a few minutes. So most of what we know about the Venusian surface comes from Magellan -- a spacecraft that rolled back the clouds from our bright neighbor.
More about the evening lineup tomorrow.
Script by Damond Benningfield, Copyright 2010
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