The moon has been compared to all kinds of these things, but this might be the first time for a raisin. The analogy comes from NASA in regard to a new study in Nature Geoscience showing that the moon is still shrinking as its interior cools. "Just as a grape wrinkles as it shrinks down to a raisin, the Moon gets wrinkles as it shrinks," explains NASA. The difference is that the moon doesn't have the flexible skin of a grape. Instead, its brittle surface cracks as it shrinks, resulting in "thrust faults," or cliffs akin to stair steps, per CNN. The key takeaway from the study is that the moon is more active in this regard than was previously thought, which could have ramifications for, say, the location of a future outpost, reports National Geographic.
"The whole idea that a 4.6-billion-year-old rocky body like the moon has managed to stay hot enough in the interior and produce this network of faults just flies in the face of conventional wisdom," says study coauthor Thomas Watters of the Smithsonian Institution. Evidence of such moonquakes were recorded by astronauts using seismometers in missions between 1969 and 1977, and the new study shed more precision on the nature of those quakes. Thousands of resulting cliffs now dot the surface, and in a 1972 landing, astronauts had to zig-zag their rover over one such fault scarp named Lee-Lincoln. As far as the moon's shrinking, it's not a lot—the moon has gotten about 150 feet "skinnier" in the last several hundred million years, per NASA. (Read more moon stories.)