Researchers have discovered the surprising reason

Thermal lunar earthquakes on the Moon are as reliable as clockwork. But the second type of earthquake raises new questions and offers exciting answers.

PASADENA – The moon trembles every afternoon. These small moonquakes are as reliable as clockwork because they depend on conditions on the moon’s surface. Since Earth’s moon has no atmosphere, temperatures there vary greatly. The sun’s temperature at midday reaches 130 degrees Celsius, while in the dark of night it reaches -160 degrees Celsius. These extreme temperature differences cause small thermal moonquakes: when it is hot, the Moon’s surface expands and when it is cold, it contracts.

In 1976, the crew of NASA’s Apollo 17 lunar mission placed three seismometers on the Moon that were able to detect these lunar quakes, and they did so from October 1976 to May 1977. A team of researchers led by Francesco Civellini of the University of California Caltech analyzed this data using new methods and were able to prove that moonquakes are surprisingly accurate. Every afternoon, as the Sun leaves its zenith and the Moon’s surface begins to cool, the Earth shakes.

Not all lunar earthquakes have a natural cause

However, in the course of the analyses, the research team was able to identify a second type of moonquake that occurs at a different time of the day: in the morning, quakes that are non-thermal in nature seem to occur. The research group made a surprising discovery: the second type of lunar earthquake is not of natural origin, but is due to the lander with which the astronauts landed on the Moon, which was partially left on the surface – too close to the seismometers.

“Every lunar morning, as the sun hits the lander, it begins to crack,” study co-author Allen Husker explains in a paper. notice. “Another one every five to six minutes, over the course of five to seven Earth hours. “It was incredibly regular and frequent.” The new study was In the magazine Journal of Geophysical Research – Planets published.

Science wants to understand the processes occurring on the Moon

It is important for science to understand the processes taking place on the Moon, as people are expected to land on Earth’s satellite again in the next few years. There are also plans to establish research stations on the moon in the medium term. Although thermal lunaquakes are too weak for humans to feel, they provide researchers with valuable information for future lunar missions — for example, how the lunar module should be designed to withstand extreme temperature conditions on the Moon.

Lunar quakes also allow scientists to get a deeper look at the soil of Earth’s satellite. When seismic waves move through different materials, researchers can analyze them — which is how geologists also study the Earth’s interior. “We hope to be able to map underground craters and look for deposits,” Husker explains.

Lunar quakes can be used to study water

The scientist adds: “There are also certain areas in the craters located at the south pole of the moon that never see sunlight; They are constantly in the shadows. If we could put a few seismometers in there, we could look for water ice that might be trapped underground; Seismic waves travel more slowly through water.

Since there are no plate tectonics or volcanic activity on the Moon, researchers rely on thermal lunar earthquakes to study the interior of Earth’s satellite. “It is important to know as much as possible about the existing data so that we can plan experiments and missions to answer the right questions. The Moon is the only planetary body besides the Earth that has more than one seismometer at the same time. It gives us the only opportunity to accurately examine another body,” Hosker stresses. . (unpaid bill)

Automated assistance was used in writing this article by the editorial team. The article was carefully examined by editor Tanya Banner before publication.