Tuesday, April 11, 2006
With preliminary plans for a permanent base on the moon under way at NASA, one of the less obvious engineering challenges is moonquakes. The Apollo astronauts installed a total of 4 seismometers on the moon. The seismometers radioed their data back to earth until they were turned off in 1977. The moonquakes recorded fell into 4 broad categories, three of which are quite mild and generally harmless. However the fourth type, called shallow moonquakes, could pose a significant challenge to moonbase designers. According to Clive R. Neal, associate professor of civil engineering and geological sciences at the University of Notre Dame, of the 28 shallow moonquakes recorded between 1972 and 1977, there were some that "registered up to 5.5 on the Richter scale." That is powerful enough to rearrange your furniture and crack plaster. In addition, they all lasted longer than 10 minutes! (A typical earthquake will last about 1 minute or so.) As you can imagine, any moonbase would have to be built from flexible materials that can withstand prolonged and repeated shaking in order to prevent any cracks or leaks from developing in a moonquake. Turns out this space exploration thing isn't so simple. NASA press release about the story.