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The moon, as seen from Tehran, Iran, in March.

The moon, as seen from Tehran, Iran, in March.

Photograph by Siamak Sabet, My Shot

Ker Than

for National Geographic News

Published September 17, 2010

This Saturday night people will be gathering in groups around the world to examine Earth's nearest celestial neighbor as part of the first ever International Observe the Moon Night.

The global event is a joint project between NASA and several partners to raise awareness about the scientific importance of the moon, such as studying how the solar system formed or planning any future human missions to the lunar surface.

"If we can get people to notice the moon a little more, they might notice it when it's in the news," said Andy Shaner, a spokesperson for the Lunar and Planetary Institute in Houston, which is helping to coordinate the event.

(Find out more about the origins of International Observe the Moon Night.)

Around 370 official events are currently scheduled in nearly 50 countries. But people can have their own moon party from just about anywhere, Shaner said.

"The great thing about this is you could have your own event on your back porch while barbecuing with your friends," he said. "Or you can go to your local observatory. It's anything you want to do."

To observe features on the moon, a telescope or binoculars are helpful but not required, said Mark Hammergren, an astronomer at the Adler Planetarium in Chicago.

"The thing about observing the moon that is just so wonderful is that it's a really bright target," Hammergren said. "It's accessible to people everywhere. You don't have to go to dark skies or travel hours outside of the city."

On the night of September 18, the moon will be in a waxing gibbous phase—a prime time for lunar observations. (Take a moon quiz.)

"A lot of people like to look at the moon when it's full," Hammergren said. "But that's when the sun is hitting it straight on, so you don't get the big shadows" that help bring out details of the moon's topography.

(See "Year's Biggest Full Moon, Mars Create Sky Show.")

As for what to look for, Hammergren shared some of his moon highlights:

Craters Galore

The moon's many craters are some of the easiest features to examine. For example, Tycho crater on the moon's southern hemisphere is visible even to the naked eye.

"You can pick it out as a brightish spot on the moon, but a telescope will reveal it to be a crater for sure," Hammergren said.

(See some of the first pictures from NASA's Lunar Reconnaissance Orbiter.)

Mountain Sunrise

During a waxing gibbous moon, people on Earth can clearly see the line that separates the moon's day and night sides. Called the terminator, this line is the best place to find features such as mountains and cliffs that can cast long shadows on the moon's surface.

"It's the very best part of the moon to look at, because it really lets you see the terrain features," Hammergren said.

"Sometimes you can see the very tips of mountains that were in the darkness actually start to get lit up. What you're watching is sunrise on the moon."

Lunar Lava Channels

One of Hammergren's favorite features on the moon are lunar rilles, channels on the moon carved out long ago by flowing lava.

"The most famous is Hadley Rille, where the Apollo 15 spacecraft moon lander came down near," he said. Hadley Rille is centrally located in the moon's northern hemisphere, and can be a challenging but rewarding target for more advanced telescope users.

(Related: "The Moon Has Shrunk, and May Still Be Contracting.")

Man on the Moon

The moon's surface is a mottled mix of light soil and dark lava plains called maria. This pattern creates an optical illusion that, for some, suggests the face of a man.

"Other cultures see other things, such as a rabbit or a goddess," Hammergren said. In Chinese culture, for example, the dark plains make up the silouhette of a rabbit, the companion to the mythological character Chang'e.

(Related: "China's First Space Walk Mission a Step Toward the Moon?")

Volcanic Domes and Pits

If you do see the man on the moon, you might notice bumps and pits on his face. These are volcanic domes and collapsed parts of the lunar surface called scarps.

"You can pick them out near the moon's terminator," Hammergren said. (See a picture of a pit on the moon.)

Those new to sky-watching, he added, should try to observe the moon when it is high above the horizon, because that's when light from the lunar disk isn't distorted by Earth's lower atmosphere.

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