page_title: Moon
section_title: Human impact
hierarchical_section_title: Moon / Observation and exploration / By spacecraft / Human impact
caption_attribution_description: English: Apollo 17's LEAM experiment.
context_page_description: The Moon is an astronomical body orbiting Earth and is the planet's only natural satellite. It is the fifth-largest satellite in the Solar System, and by far the largest among planetary satellites relative to the size of the planet that it orbits. The Moon is, after Jupiter's satellite Io, the second-densest satellite in the Solar System among those whose densities are known.
  The Moon is thought to have formed about 4.51 billion years ago, not long after Earth. The most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a hypothetical Mars-sized body called Theia. New research of Moon rocks, although not rejecting the Theia hypothesis, suggests that the Moon may be older than previously thought.
  The Moon is in synchronous rotation with Earth, and thus always shows the same side to Earth, the near side. Because of libration, slightly more than half of the total lunar surface can be viewed from Earth. The near side is marked by dark volcanic maria that fill the spaces between the bright ancient crustal highlands and the prominent impact craters.
context_section_description: Beside the traces of human activity on the Moon, there have been some intended permanent installations like the Moon Museum art piece, Apollo 11 goodwill messages, Lunar plaque, Fallen Astronaut memorial and other artifacts.
caption: Remains of human activity, Apollo 17's Lunar Surface Experiments Package
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