EARTH'S MOON

                                         EARTH'S MOON

 Earth's moon took form in a cosmic collision about 4.5 billion years ago, shortly after our planet formed. An object about the size of Mars struck Eve Earth, blasting large fragments of the planet into orbit. This orbiting matter eventually coalesced into the moon, which has a composition very similar to that of Earth's crust. The moon's original molten   surface cooled over time and then was intensely bombarded by space debris, which created the many craters visible on its surface today. Next, molten rock
      welled up from the moon's interior and flooded the impact basins, creating the moon's seas, called maria.. Eventually the tumult died down and the moon turned into the quiet, dusty, rocky world that greeted the Apollo  astronauts in 1969, when Earth's  moon became the first extraterrestrial body visited by humans. Our planet's sole natural satellite, the moon is one-fourth the size  of Earth and the fifth largest satellite in the solar system. Some astronomers have suggested that Earth and it moon are close enough in size that they should be considered a double-planet system. The Lunar Reconnaissance Orbiter, dubbed "NASA's first step back to the moon," will add to our lunar knowledge.
      
 THE MOON'S SPIN has been slowed by gravitational interactions with both the sun and Earth, so that its rotational speed equals that at which it revolves around Earth. Thus, the same side of the moon consistently faces Earth. Astronomers could only speculate about the landscape of the far side of the moon until the  images brought back by the Soviet space probe Luna 3 in 1959.  

THE MAN IN THE MOON? Some cultures see a hare, whereas others see a frog, a moose, or a woman's silhouette. But many people see a man's face: eyes, nose, and mouth. The topography results from events some four billion years ago. Internal lava flow and other volcanic action caused magma to flood the surface and harden into the features we see today.