Guys aren't the only ones who experience shrinkage. It can happen to anyone — or, apparently, anything. A study published in the October issue of the journal Geology suggests that the ridges and cracks researchers have observed in the Moon's crust are the result of Earth's gravitational pull. Scientists first noticed that the Moon is shrinking — and cracking — in 2010, when they analyzed images taken by NASA's Lunar Reconnaissance Orbiter (LRO). But it wasn't until recently that they determined that the shrinkage is most likely the Earth's fault.
"What [the researchers] figured out is that the tidal forces of the Earth pulling on the Moon, while small, generated enough stress to break the Moon's crust," The New York Times explains. The scientists, led by Dr. Thomas Watters of the Smithsonian National Air and Space Museum, have observed about 3,200 ridges — or, as the scientists call them, "scarps" — in the Moon's crust, and they don't think the Moon will stop cracking (and shrinking) anytime soon. So what tipped off the scientists that the Earth was responsible for the Moon's cracks? The geologists note in the study that many of the cracks are recent, and the Moon's ridges are still "actively forming" on a regular basis.
In addition to the timeline of the Moon's shrinking, the researchers noted that the ridges weren't random, but appeared to run north-south near the equatorial lines, while they ran from east to west near the poles. If the cracks were from standard processes on the Moon, the shrinkage would occur on a more scattered basis, with the cracks pointing in a variety of directions.
When the researchers first began studying NASA's images of the Moon's ridges, they only had information from 10 percent of the Moon's surface. The initial research only led them to find 14 ridges. But now, the LRO has taken images of more than 75 percent of the Moon, allowing the scientists to study the patterns of the 3,000-plus ridges.
"The discovery of thousands of young fault scarps, influenced by tidal forces from Earth, is an exciting new dimension to our understanding of the close relationship between our planet and the Moon," Dr. Watters said in a statement released Tuesday. "Exciting" is definitely an optimistic way to look at the fact that the Moon is getting smaller. We're pretty fond of the Moon, so the idea that it's shrinking is pretty alarming. Luckily, though, when the scientists first discovered the cracks, they were quick to note that the shrinkage is "so small that you would never notice it. The Moon "will not shrink out of view in the future."
And similar faults aren't unusual for planets. When scientists found the cracks in 2010, they assumed that they were the result of the Moon's core cooling and getting smaller, a process that's common on Mercury. The Times notes that similar cooling and contraction processes happen to "all planetary bodies" — even Earth — and the overall effect on the planets' size is negligible. So it's safe to say that your favorite Earth-orbiting rock isn't going anywhere.
