The Moon

The Moon is the only natural satellite of the Earth, and the fifth largest satellite in the Solar System. It is the largest natural satellite of a planet in the Solar System relative to the size of its primary, having a quarter the diameter of Earth and ¹⁄₈₁ its mass. The Moon is the second densest satellite after Io, a satellite of Jupiter. It is in synchronous rotation with Earth, always showing the same face; the near side is marked with dark volcanic maria among the bright ancient crustal highlands and prominent impact craters. It is the brightest object in the sky after the Sun, although its surface is actually very dark, with a similar reflectance to coal. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art and mythology. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day. The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to appear almost the same size in the sky as the Sun, allowing it to cover the Sun nearly precisely in total solar eclipses.

The Moon is the only celestial body on which humans have set foot. While the Soviet Union's Luna programme was the first to reach the Moon with unmanned spacecraft in 1959, the United States' NASA Apollo program achieved the only manned missions to date, beginning with the first manned lunar orbiting mission by Apollo 8 in 1968, and six manned lunar landings between 1969 and 1972, with the first being Apollo 11. These missions returned over 380 kg of lunar rocks, which have been used to develop a detailed geological understanding of the Moon's origins (it is thought to have formed some 4.5 billion years ago in a giant impact event involving Earth), the formation of its internal structure, and its subsequent history.

After the Apollo 17 mission in 1972, the Moon has been visited only by unmanned spacecraft, notably by the final Soviet Lunokhod rover. Since 2004, Japan, China, India, the United States, and the European Space Agency have each sent lunar orbiters. These spacecraft have contributed to confirming the discovery of lunar water ice in permanently shadowed craters at the poles and bound into the lunar regolith. Future manned missions to the Moon have been planned, including government as well as privately funded efforts. The Moon remains, under the Outer Space Treaty, free to all nations to explore for peaceful purposes. 

Images from this page were published in the Sky & Telescope Magazine's Photo Gallery.

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		Taken on 4/17/2008 Modified Canon Rebel XT 350D Orion ED80 Single Exposure 1/1000 ISO 400 Focused with DSLRFocus Processed with PhotoShop CS
Mare Crisium (Sea of Crises)		Taken on 8/1/2007 Unmodified Canon Rebel XT 350D Orion ED80 Single exposure 0.3 seconds ISO 800 Mare Crisium (the "sea of crises") is a lunar mare located in the Moon's Crisium basin, just northeast of Mare Tranquillitatis. This basin is of the Nectarian epoch, while the mare material is of the Upper Imbrian epoch. This mare is 376 miles (605 KM) in diameter, with many notable features in and around it. The cape-like feature protruding into the southeast of the mare is Promonitorium Agarum. On the western rim of the mare is the palimpsest Yerkes. The crater Picard is located just to the east of Yerkes, and northwest of Picard is the crater Peirce. [*]
		Lunar Eclipse of March 3, 2007.  No filters used.
		March 27, 2007 Photo taken with an Unmodified Canon RebelXT 300mm zoom lens, f/5.6 on a fixed tripod.