The latest discovery about the Moon holds great significance for NASA. Just a few days after India’s Chandrayaan-3 spacecraft detected a “natural” seismic event on the Moon, scientists have revealed that the Moon is not a tranquil place, and its surface regularly experiences “thermal quakes” due to extreme temperature variations.
The Vikram lander touches down on the Moon. Photo: ISRO/India Today
However, it’s not just the temperature differences that cause these “thermal quakes,” but also the recent discovery of mysterious tremors.
So, what is this issue all about?
The Moon experienced geological activity from 3.7 to 2.5 billion years ago, leaving behind evidence in the form of dormant volcanoes, lava flows, and other geological features.
Despite billions of years of geological stability, the Moon still undergoes minor seismic events due to the gravitational forces of Earth and the Sun, as well as sudden temperature changes. These events occur regularly and are referred to as “moonquakes.”
Scientists explain that the Moon, lacking an atmosphere to regulate temperature, experiences significant temperature swings, ranging from 120 degrees Celsius during the day to -130 degrees Celsius at night. This causes the Moon’s surface to expand and contract, leading to vibrations and small cracks called “thermal quakes.”
The Moon is influenced by the gravitational forces of both Earth and the Sun. Photo: NASA
In 1972, astronauts on the Apollo 17 mission placed seismometers on the Moon’s surface to measure its activity. These highly sensitive instruments could record even the slightest vibrations on the Moon’s surface. The sensors collected data for a period of eight months, from October 1976 to May 1977, and much of the data remained unprocessed until recently.
In a recent study sponsored by NASA, a team of researchers led by Francesco Civilini, a postdoctoral researcher at the California Institute of Technology (USA), currently working at NASA’s Marshall Space Flight Center, examined the Moon’s seismometer data using machine learning.
Joining him were Renee Weber, a planetary scientist at NASA’s Marshall Space Flight Center, and Allen Husker, a professor of geophysics at the California Institute of Technology.
Surprising Discovery on the Moon
Their analysis revealed that thermal quakes occur regularly every morning as the Sun moves away from its zenith, and the Moon’s surface rapidly cools. However, the model also detected seismic signals in the morning that differed from evening quakes.
The researchers were able to identify the source of this activity and found that the mysterious morning tremors on the Moon were recorded by the seismometer on the Apollo 17 spacecraft, not caused by seismic events from India’s Vikram lander.
The landing module of the Apollo 17 spacecraft is causing small moonquakes. Photo: Public Domain / NASA / Harrison Schmitt
Each morning, as the Sun’s light touches the lunar module, the spacecraft’s surface expands, causing small vibrations in the ground recorded by the seismometer.
Allen Husker, a professor of geophysics and co-author of the new study, explained: “Every morning, when the Sun hits the lunar module, the spacecraft’s surface expands. Every 5 to 6 minutes (equivalent to 5 to 7 Earth hours), there is a vibration. They are regular and repeat surprisingly.”
This valuable data holds significant importance for future missions to the Moon, including NASA’s Artemis program. While the thermal quakes are too small for anyone on the Moon’s surface to feel, these discoveries provide essential information that can inform the design of future equipment and lunar landers.
It can also provide insights into the construction of future lunar bases, such as the Artemis Base Camp, the International Lunar Research Station (ILRS), and ESA’s proposed Moon Village, where composite materials would be used instead of alloys to avoid causing local seismic disturbances.
Furthermore, seismic activity is a useful tool for probing the interiors of celestial bodies and can be used to infer the structure of these bodies and locate materials (such as water ice) beneath the surface.
“We hope to map impact basins under the Moon’s surface and look for deposits. Moreover, if we could place some seismometers in the Moon’s polar regions, we could search for subsurface ice; seismic waves travel slower in water,” explained Professor Allen Husker.
Despite the absence of tectonic plate movements or volcanic activity on the Moon, many questions about its internal structure remain unanswered. This study marks a significant step in gaining a better understanding of our nearest celestial neighbor.
“The Moon is the only celestial body other than Earth with multiple seismometers at once. It gives us the unique opportunity to study another celestial body in detail,” concluded the group of authors.