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Three planets and a crescent moon will light up the western sky shortly after sunset this evening (Feb. 22). Created with Stellarium

Mercury makes its move into the evening sky

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Wadena Minnesota 314 S. Jefferson, P.O. Box 31 56482

Move over Jupiter. Move over Venus. It may be the smallest planet, but Mercury is on its way up into the evening sky. Beginning tonight - and with the help of a very young crescent moon - observers with clear skies and a wide open western horizon can seek the innermost planet alongside the 1-day-old moon. As always, take your binoculars to help in case the sky is less than ideal.

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The duo will be well below the Venus-Jupiter line just five degrees or three fingers held together at arm's length above the west-southwest horizon. The best time to look is starting about 20 minutes after sunset. Don't wait too long or they'll set before you get the chance to see them.

As we move into late February and early March, the moon will move up and away from Mercury and pass near Venus on the 25th and Jupiter on the 26th. Mercury also moves up and away from the sun and will soon become much easier to see. I'll keep you posted on good viewing opportunities coming up.

Two nearly complete maps of the planet Mercury made from pictures taken by the MESSENGER spacecraft in orbit around the planet. The black and white map is more detailed than the color version, which highlights different types of minerals and terrains. Credit: NASA

NASA's Mercury MESSENGER (Mercury Surface, Space ENvironment, GEochemistry, and Ranging) mission has nearly completed its initial mission goal of mapping the planet in color and black and white. It's also made quite a few discoveries including:

* Most of Mercury's mass - 60-70% vs. 32% for Earth is in the form of metal in its core. Lighter materials were either boiled away from intense solar heat and solar wind bombardment or from heating caused by a major impact long ago. Mercury is 36 million miles from the sun or 2.5 times closer than the Earth. Surface temperatures are as hot as 800 degrees and sunlight 6.5 times more intense than on Earth.

Shallow, flat-bottomed pits on Mercury may be caused by subatomic particles from the sun zapping away at sulfur-laden minerals. Credit: NASA

* Like Earth, Mercury is surrounded by a magnetic field, but it's offset far to the north of the planet's center and fluctuates over time. Compared to the planet's small size (3032 miles or about 1.5 times the size of the moon), this offset is far more than any other planet. Scientists are still at a loss to explain why.

* A vast expanse of volcanic plains with lavas as thick as 1.2 miles surround the north polar region. According to James Head of Brown University, the deposits appear to be flood lavas or huge volumes of solidified molten rock similar to those in the Columbia River basin in the northwest United States. "Those on Mercury appear to have poured out from long, linear vents and covered the surrounding areas, flooding them to great depths and burying their source vents," said Head.

* New, unexpected landforms called 'hollows' have been discovered inside some of the planet's craters. The shallow, rimless pits range from about 100 feet to 2 miles wide are often seen in clusters. They're very reflective and appear quite fresh. Scientists believe the intense solar wind felt at Mercury's distance may be eating away at exposed sulfur deposits on the surface to create the depressions.

* Mercury's surface may look like the moon, but its rocks contain lots more potassium and sulfur than the lunar variety.

If you'd care to learn more about the new findings and see additional photos of Mercury, check out the MESSENGER website. And don't forget to go out and see the planet with your own eyes in the next few weeks.

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