The Moon is shrinking, and there’s nothing you can do about it.
Researchers led by the Smithsonian National Air and Space Museum’s Thomas R. Watters first reported the shrinkage, which has taken place over a billion years, as the Moon’s core cooled and contracted, in 2010. Watters’ team, surveying about 10 percent of the lunar surface, identified 14 cracks and ridges in the moon’s surface; five years laters, scientists have identified more than 3,200.
According to the New York Times, if the moon were shrinking uniformly, the ridges—formed when the moon’s surface cracks and one side of the fracture slips over the other—would be distributed randomly around the face of the heavenly body. However, Watters’ team found a preponderance of north-south ridges in the equatorial and midlatitude regions and east-west ridges near the poles.
In a study published in Geology, Watters and his colleagues theorize that this pattern is a result of the Earth’s tidal forces pulling on the Moon. From the study’s abstract:
Lunar Reconnaissance Orbiter Camera images reveal a vast, globally distributed network of over 3200 lobate thrust fault scarps, making them the most common tectonic landform on the Moon. Based on their small scale and crisp appearance, crosscutting relations with small-diameter impact craters, and rates of infilling of associated small, shallow graben, these fault scarps are estimated to be younger than 50 Ma and may be actively forming today. The non-random distribution of the scarp orientations is inconsistent with isotropic stresses from late-stage global contraction as the sole source of stress. We propose that tidal stresses contribute significantly to the current stress state of the lunar crust. Orbital recession stresses superimposed on stresses from global contraction with the addition of diurnal tidal stresses result in non-isotropic compressional stress and thrust faults consistent with lobate scarp orientations. The addition of diurnal tidal stresses at apogee result in peak stresses that may help trigger coseismic slip events on currently active thrust faults on the Moon.
Damn.
“The kind of radius change and shrinking we’re describing here is so small that you would never notice it,” Watters said in 2010. Haha, it’s all right, man—happens to the best of us.
Photo credit: AP Images. Contact the author of this post: brendan.oconnor@gawker.com.