Our own moon is only 240,000 miles (384,000 km) away. This is more than 150 times closer than the planet Mars. Because it is nearby and easy to reach, earth's moon will probably be the first stop for future space tourists. And why not? It's certainly not lacking in Kodak moments. Aside from obvious tourist attractions, such as the Apollo 11 landing site, there are some natural wonders that rival anything found on earth or the other planets and satellites. Just for starters...
1. There is a small crater named Peary that lies directly on the north pole of the moon. Appropriately enough, it is named after Robert Peary, the Arctic explorer who first reached earth's north pole (unless you're talking to a fan of Dr. Cooke).
Since the sun never gets very far above the horizon, the bottom of the crater is in perpetual darkness. The only illumination might be eerie blue earthlight when our planet is above the horizon. Likewise, the sun never sets on some of the peaks of the crater rim. Even though the crater itself and much of the landscape around it may be in darkness, these peaks will always shine brilliantly. The more poetically inclined astronomers have dubbed these peaks "The Mountains of Eternal Light", which has to be one of the most romantically named places in the solar system.
2. Even seen from earth, Copernicus crater is one of the moon's most beautiful sights. It lies not too far from the center of the moon as seen from earth. At 58 miles wide, it is easily visible through a pair of binoculars: a bright crater surrounded by a white halo, sitting by itself in the midst of a dark plain. It is about the same size as Yellowstone Park on earth.
Standing on the crater rim, you are more than 0.5 mile above the surrounding plain. In front of you are the terraced slopes of the crater, leading to the floor nearly 2.5 miles below. Unlike most other large craters on the Moon, Copernicus was never filled with lava, so its floor is deep and bowl-like with a cluster of towering peaks in the center, three of them rising more than 4,000 feet.
3. A lunar Bali Hai, Mount Pico is a lone, pyramid-shaped mountain rising 8000 feet (1.5 miles) above the surrounding flat lunar landscape. It is part of a ring of mountains that once completely surrounded a giant impact crater.
Unlike Copernicus, however, this crater was flooded with lava, creating a vast, flat, circular plain called the Mare Imbrium. Most of the ancient mountains were buried under the lava and only a few isolated peaks remain, like islands in a sea of stone.
4. The great Alpine Valley splits an entire mountain range in half. The valley is 103 miles long and over 6 miles wide. Alpine Valley was created when the surface of the Moon split along a fissure or crack in the surface.
The two sides pulled apart, leaving the deep valley between. The flat floor was once flooded with the lava that poured from the enormous wound in the lunar crust. Running down the middle of the valley is a narrow winding channel called a rille, which was originally a lava tube (a kind of tunnel through which molten rock once flowed) which collapsed after the lava drained away.
5. The Straight Wall is an enormous lunar cliff—-or, more accurately, a scarp. Its official name is Rupes Recta, Latin for (wait for it) "straight cliff". Like Mt. Pico, it lies all by itself in a flat, smooth plain and is easy to spot through a small telescope. The wall is almost perfectly straight (so it has sometimes been called "the railroad") and nearly 75 miles long.
It was created when a huge block of the lunar crust was thrust upward along a fault or crack. Estimates of its height range from 820 to 1,300 feet: by comparison, the Great Wall of China is only 30 feet high
6. The South Pole-Aitken Basin is the largest crater on the Moon. At 1,392 miles in diameter and 8 miles deep it is also one of the largest known craters in the entire solar system.
A geological map of the moon showing the location of the South Pole-Aitken Basin, the blue area surrounded by the dotted black line.
The result of a collision with an asteroid millions of years ago, if the same crater were on Earth, it would stretch from New York to Kansas City. Unfortunately for our tourists, it is too big to see from the surface and can only be appreciated from orbit.
7. The Natural Bridge was one of the biggest recent surprises astronomers discovered on the lunar landscape, largely because most natural bridges on earth are the result of wind or water erosion...and the moon is notably lacking in both.
In this case, the bridge was created when a lava tube collapsed in two places, leaving a section more than 60 feet long and as wide as a two lane highway still in place. A second, smaller bridge was also discovered nearby.
There are many other candidates for the Seven Wonders of the Moon. Tycho, Hadley Rille, Aristarchus, etc. come to mind. It will be interesting to see what potential wonders readers will suggest!
Illustrations by Ron Miller
Photos from NASA