As if vacuum, intense cosmic radiation, corrosive dust, meteors, and drastic changes in temperature by hundreds of degrees between day and night were not enough, personnel at future lunar bases will also face tremendous dangers from moonquakes.If you read a lot of science fiction, you might think that the main threats to a moon base are hostile flying saucer attacks, the incredibly incredible Catwoman, and meteor showers. Now, according to research by a team of scientists led by Thomas R. Waters, emeritus senior scientist at the University of Maryland Smithsonian, another problem facing future base commanders is moonquakes.
Apollo 17 mission commander Gene Cernan
This new bad news comes from an assessment based on data brought back by the Apollo 17 astronauts. In December 1972, the Apollo 17 astronauts landed in the Taurus-Littrow Valley, located on the southeastern edge of the Mare Chengdu. This rugged, mountainous area was chosen as the landing site for America's last Apollo moon missions because of its geology and its ability to maximize the science brought back by astronauts Eugene Cernan and Harrison Schmidt.
Apollo 17 landing site
Although the six Apollo lunar missions left behind instruments, including seismometers, their performance was very limited and they were all shut down in 1977 as the nuclear power source began to malfunction. As a result, our understanding of lunar geological activity, especially earthquakes, is very limited.
So the Maryland team turned to other clues to learn more about the moon's seismic activity. Specifically, they looked at boulder falls and landslide samples collected by astronauts at Taurus-Littrow Space Center. They found that these falls and landslides were caused by ground movements caused by earthquakes, rather than large meteor impacts, which are too rare to produce the required shock waves.
These earthquakes occurred over a period of 90 million years and had a magnitude of approximately 3.0 on the Richter scale. On Earth, such earthquakes are very mild and may be felt, but are unlikely to cause any damage. On the moon, especially if it's a shallow earthquake, the impact would be much greater.
Astronaut Harrison Schmidt collecting samples
In addition to telling scientists more about the moon's small but still present geological activity as it continues to shrink, the findings also suggest that the danger of disrupting human outposts on the moon is great enough that planners need to keep it in mind.
This danger is not entirely a high-probability event. On any day, the probability of encountering a moonquake is about one in 20 million, but for a long-term lunar base, the probability drops to one in 5,500 over the course of a year, and the longer you stay on the moon, the lower the probability. There are also problems with the design of future landers, which tend to be tall, top-heavy and prone to tipping over if the ground shakes — as has been the case with recent robotic landers.
The team acknowledges that this is based on a small amount of data, but believes that lunar orbiters equipped with high-resolution cameras and new seismic stations as part of the Artemis program will help fill in these knowledge gaps.
"We want to make sure lunar exploration is safe and that investments are well thought out," said Nicholas Schmer, associate professor of geology at the University of Maryland. "We came to the conclusion: Don't build on fault scarps or faults that have been recently active. The further away from the fault scarp, the less risk there is."
The research was published in Science Advances.