How many new craters have formed on the moon in the last seven years? The answer is higher than most might have guessed: 222. And it turns out, these new lunar craters are occurring more quickly than scientists once thought, reports Space.com’s Charles Q. Choi.
The new study, published in the journal Nature, suggests that lunar crater formation is 33 percent higher than predicted. Using imagery from NASA’s Lunar Reconnaissance Orbiter, which collects a wide range of data about the moon and its environment, the team found 222 new craters that had appeared on the surface of the moon since the LRO took its first images in 2009.
As The Los Angeles Times’ Amina Khan explains, it’s pretty hard to compare images to identify craters, requiring many hours to manually trawl through the snapshots and identify new marks in the pocked lunar surface. So the team designed a computer program to do the comparisons for them. In total, the program compared images from about six and a half percent of the moon’s surface—that's 14,092 pairs of before-and-after photos.
They also studied how comets, meteorites and other objects bombard the moon, creating craters. The before-and-after photos showed zones around the craters that seem to be left by what they call jetting—a phenomenon that happens when the shock wave of impact produce material that jets outwards at a high velocity. The rock hit by the object vaporizes or melts, and these jets can spread to hundreds of crater widths away from the area of initial impact.
That phenomenon doesn’t just create a distinctive zone around the crater—it also indicates potential danger to future moon dwellers. According to a NASA press release, it implies “that equipment placed on the moon for long durations—such as a lunar base—may have to be made sturdier.” A greater number of impacts combined with a larger ring of influence mean that equipment left on the moon could be in peril.
The study also revealed other, previously unknown facts about lunar craters. For example, the time required to churn up the top 0.8 inches or so of the moon’s surface is 100 times less than previously thought. That will not only impact plans for future lunar bases, but also the current historical traces on its surface.
“The newly determined churning rate means that the Apollo astronaut tracks will be gone in tens of thousands of years rather than millions,” Mark Robinson, an Arizona State University space geologist who co-wrote the paper, says in the NASA release. Like all good things, the iconic Apollo footprints will one day come to an end—just a little bit earlier than anyone foresaw.