The Moon still has many secrets

Moonquakes are known to exist. The reasons are still partly unknown.

Moonquakes are known to exist

Professor Karri Muinonen from the Department of Astronomy says that moonquakes differ from earthquakes in terms of their birth mechanism and intensity.

“There are no tectonic plates on the Moon. The actual lunar quakes take place deeper than 800 kilometres under the surface and they are caused by tidal forces exerted by the Earth. Moonquakes are notably weaker than earthquakes,” says Muinonen.

“We can detect certain cyclic features in these deep moonquakes, which correspond with the length of the month. The surface of the Moon is also disturbed by small asteroid impacts. Recently, high frequency shallow quakes, approximately 100 kilometres deep, have been detected, but the cause for the phenomenon is not yet known."

Moon research is entering a renaissance and attempts are being made to find suitable locations for a manned space base.

“The idea is to make use of the minerals and elements in the immediate surroundings so that not everything needs to be transported from Earth."

Setting up a base on the Moon is just an intermediate step. The next step is to travel to Mars. Moon researchers are, however, still discussing the origins of the Moon.

“The prevailing theory at the moment is that the Moon was born out of a collision of the Earth and an object the size of Mars. The impact caused material to build up into the body we call the Moon and which orbits our home planet. In the future, we will know more about how the Moon came into being,” says Muinonen.

July 21 marks 40 years since the first Moon landing. The crew of Apollo 11 set up a seismometer on the surface of the Moon, and there is an image of vibrations recorded by the device on the wall of the Department of Seismology at Kumpula campus. The picture frame also holds a snapshot of a moonwalker.

The picture was given to the department by an American engineer, Howard April, and his wife.

“I suspect he knew the people who built the seismometer for the trip,” says Katriina Arhe, the department secretary.

April learnt to know Finnish seismologists when he was installing seismic equipment in Utsjoki Kevo and Nurmijärvi. He subsequently married the librarian of the Department of Seismology.

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Department of Astronomy (University of Helsinki)


Text: Anna-Kaisa Kontinaho
Photo: Pasi Lindblom

Translation: AAC Noodi Oy
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