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One small grain of moon dust, one giant leap for lunar studies

Back in 1972, NASA sent their last team of astronauts to the Moon in the Apollo 17 mission. These astronauts brought some of the Moon back to Earth so scientists could continue to study lunar soil in their labs. Since we ...

How moon jellyfish get about

With their translucent bells, moon jellyfish (Aurelia aurita) move around the oceans in a very efficient way. Scientists at the University of Bonn have now used a mathematical model to investigate how these cnidarians manage ...

Huygens landing spin mystery solved

Fifteen years ago today, ESA's Huygens probe made history when it descended to the surface of Saturn's moon Titan and became the first probe to successfully land on another world in the outer solar system. However, during ...

Our favorite holiday gift? A box of Apollo moon soil

Fortunately for today's scientists, Apollo-era leaders had the foresight to save much of the 842 pounds (382 kilograms) of Moon soil and rocks retrieved by NASA astronauts 50 years ago for future generations. They figured ...

Europe powers up for third and fourth Orion spacecraft

Europe will power the NASA spacecraft that take astronauts to a new international outpost and forward to the moon, following decisions made by ESA Member States at Space19+ in Seville, Spain.

Mars Express tracks the phases of Phobos

ESA's Mars Express has captured detailed views of the small, scarred and irregularly shaped moon Phobos from different angles during a unique flyby.

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The Moon is Earth's only natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is 384,403 km, about thirty times the diameter of the Earth. The common centre of mass of the system (the barycentre) is located about 1,700 km—a quarter the Earth's radius—beneath the surface of the Earth. The Moon makes a complete orbit around the Earth every 27.3 days (the orbital period), and the periodic variations in the geometry of the Earth–Moon–Sun system are responsible for the phases of the moon, which repeat every 29.5 days (the synodic period).

The Moon's diameter is 3,474 km, a little more than a quarter of that of the Earth. Thus, the Moon's surface area is less than a tenth that of the Earth (about a quarter the Earth's land area, approximately as large as Russia, Canada, and the United States combined), and its volume is about 2 percent that of Earth. The pull of gravity at its surface is about 17 percent of that at the Earth's surface.

The Moon is the only celestial body to which humans have traveled and upon which humans have performed a manned landing. While the Soviet Union's Luna program was the first to reach the Moon with unmanned spacecraft, the NASA Apollo program by the United States achieved the only manned missions to date, beginning with the first manned lunar mission by Apollo 8 in 1968, and six manned lunar landings between 1969 and 1972- the first being Apollo 11 in 1969. Human exploration of the Moon temporarily ceased with the conclusion of the Apollo program, although a few robotic landers and orbiters have been sent to the Moon since that time. The U.S. has committed to return to the moon by 2018.

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