|Home||Articles||Guide to Observing||Tour of the Constellations||Book Reviews|
While people have seen the features of the Man in the Moon for millennia, it was not until Galileo directed his telescope at it that it became known that those features are not merely painted on the Moon's surface. Galileo discovered by measuring the shadows of the Moon that it had mountains of great height. One must not get carried away and think of the Moon's topography as Earth-like. Its surface is quite unearthly. A lunar mountain range is unlike its earthly counterpart.
The lunar features that create the face of the Man in the Moon are its large plains, called seas. The naming of these areas as seas is one of the two great misnomers of space nomenclature; the other is the "canals" of Mars. The dark areas of the Moon reminded Galileo of water and thus he assumed they were seas and oceans. Although Galileo was totally wrong, and there is not nor has there ever been, any water in the lunar seas, these areas are still called by the Latin word for sea: "mare". The lunar seas are picturesquely named after states of nature and mind. The dark splotch near the right limb of the Moon consists of four connected areas - Sea of Nectar Sea of Fertility, Sea of Tranquility and Sea of Crises Most maps indicate them by their Latin names – Mare Nectaris, Mare Foecunditatiis, Mare Tranquilliitatis and Mare Crisum.
The left limb of the near side of the Moon is divided up into several areas including the Sea of Humors, Sea of Clouds, Sea of Shows and the Oceans of Storms. In Latin, these are respectively called Mare Humorum, Mare Nubium, Mare Imbrium and Oceanus Procellarum. The lunar seas are relatively smooth compared to the rest of the Moon’s surface. For this reason the Sea of Tranquility was chosen was the landing site for Apollo 11, man’s first landing on the Moon. Just before Neil Armstrong landed the lunar module, as he was about to touch-down in a crater "big enough to house The Houston Astrodome", he discovered that the Sea of Tranquility was not quite as smooth as it appeared from Earth.
Most of the surface of the Moon which is not part of a sea (this includes almost the entire far side) is thickly covered with craters. These areas appear to us on Earth as a light gray. While looking more closely at the Moon through binoculars, you will see circles of varying circumferences, which are the craters. While there are also a few craters in the lunar seas, most are concentrated in other areas. All craters have the same circular shape and they range in size from a diameter of over 100 miles across to less than a mile. A crater near limb of the Moon will appear to the viewer on Earth as an ellipse. There may be as many as 200,000 craters, most of them quite small, on the Moon's surface. A crater consists of a thin elevated ring forming its perimeter. The surface within the ring is a bit below the surrounding edge and in the center there is often a peak. An unusual feature of some craters is a series of rays emanating from the crater's edge. These rays are most easily seen when the Sun is directly shining on the near side of the Moon's surface during the full Moon. Unfortunately, it is difficult to see other features of the Moon during this time.
Nobody is absolutely sure today what formed the seas and craters of the Moon. Most likely they were created from meteors, rocks that fell from space. One might think a rock falling from a great distance above would merely create a large hole. In reality, it creates a raised circular rampart around the point of impact – in other words, a crater. The rock will be considerably smaller than the crater that it forms. Over the last 6,000,000,000 years, meteors have been falling onto the Earth. In fact considering the Moon and Earth are so close to one another, the Earth should have received as many meteors as the Moon. The big difference is that the Earth has air, which not only burns up a great deal of any meteor before it reaches the surface, but over the years, weathers away the craters that once existed. Once a crater is formed on the surface of the Moon, it stays there, at least until another meteor falls and creates another crater. The lunar seas were probably also created by falling meteors. If the lunar seas do not look as circular as craters, that is because sea’s frequent overlapping obscures their original shapes. The dark surface of the seas was created by lava that flowed over the seas after their formation and then solidified.
The surface of the Moon is no less complex than that of the Earth. Looking at it through a telescope gives me the same feeling as flying over the Earth in a plane. The following features can be seen with binoculars or better yet, with a telescope. The Moon contains several mountain ranges that are typically located in the areas between the lunar seas. One of the striking ranges is the Apennine Mountains, which is at the edge of the Sea of Showers. Its highest point is about as high as Pike's Peak. A lunar mountain range looks like an aerial view of mountain range on Earth, minus the snow-capped peaks, of course. An unusual feature of the Moon is called a rille. The rilles are channels two to three miles wide, less than one mile deep, that sometimes wind their way around other lunar features, such as lowlands and mountains, for up to 200 miles. The rilles can be seen only with the aid of a telescope.
The airless Moon is virtually unchanging in its appearance except for differences in lighting conditions. The one curious exception to this is the occasional appearance of a red mist, first observed by the Russian N.A. Kozyrev, on a peak in the crater Alphonsus. For over 25 years, people have been seeing this red mist, called a Transient Lunar Phenomenon or TLP, although nobody knows for sure what causes it, or if it really exists.