Related on TestTube:
China's Crazy Plan to Mine the Moon
Does the Moon Really Control the Tides?
The most popular theory on how the moon formed is the "giant impact hypothesis", also known as "the Big Splash". In the early days of the Solar System (about 4.5 billion years ago) a Mars-sized planet called Theia smashed into Earth and ejected material into orbit around Earth. This leftover material--mostly dust and rocks--coalesced into what is now our Moon, the Earth's only natural satellite. Some of the best evidence of this is the fact that the isotope ratios of lunar and Earth rock are identical, which implies that they came from the same place.
Although the moon may appear to us as an unchanging, barren landscape covered with craters, new surface imaging by NASA's Lunar Reconnaissance Orbiter shows that the surface of the moon is actually quite active. Distributed throughout its surface are thousands of faults, known as lobate scarps, which indicate it's under compression from the Earth's gravity, which is ever-so-slowly making it smaller by shrinking its interior and compressing the crust. The Moon's thrust faults are similar to the ones on Earth that create mountain ranges like the Himalayas. Without the Earth's gravity, the lobate scarps would be evenly distributed and have random orientations. However, imaging has revealed that most of these scarps go north-south near the Moon's equator and mid-latitude regions and go east-west at the poles. These directions are consistent with gravitational tidal forces from the Earth, according to researchers.
Click Here for More Videos About the Moon on TestTube
If the moon continues to cool and contract, it's likely new lobate scarps will form following the same patterns. The shrinking size--about 100 meters in diameter over the last billion years--is unnoticeable to us on Earth, but as the moon continues to slowly move further from us every year, its decrease in angular size will far outweigh its change in physical size. In five billion years, the Sun will expand into a red giant and possibly consume the moon, so this compression may be the least of its worries by then.
NASA's LRO Reveals 'Incredible Shrinking Moon' (NASA)
"Newly discovered cliffs in the lunar crust indicate the moon shrank globally in the geologically recent past and might still be shrinking today."
Earth's pull is 'massaging' our moon (Science Daily)
"Earth's gravity has influenced the orientation of thousands of faults that form in the lunar surface as the moon shrinks, according to new results."