Long-lasting volcanism on the dark side of the moon
Little is known about the far side of the moon. The Chinese Chang'e-6 mission is set to change that - and is delivering astonishing findings.
Once upon a time, the moon was also volcanically active, as evidenced by the rock deposits on our satellite that were brought to Earth by the Chinese lunar missions Chang'e-5 and -6, among others. The Chang'e-5 mission, for example, collected 1.7 kilograms of loose volcanic basalt material from a huge lava plain called Oceanus Procellarum in the northern part of the moon. And Chang'e-6 brought back corresponding samples from the far side of the moon. An analysis of these rocks by a team led by Qiu-Li Li from the Chinese Academy of Sciences in Beijing shows that volcanism on the far side of the moon could have lasted a long time.
The authors analysed 108 basalt fragments using a technique known as lead-lead dating, in which lead isotopes are measured to determine the age of rocks. They found that one sample with a very high aluminium oxide content was around 4.2 billion years old. The majority of the other basalt fragments, on the other hand, were significantly younger and had a uniform age of formation of around 2.8 billion years. The far side of the moon was therefore obviously particularly active at this time, before volcanism died out, at least at this point in the huge South Pole-Aitken Basin, which is up to eight kilometres deep. However, the activities could have spanned a total of 1.4 billion years - which would mean an astonishingly long period of time.
The working group hopes that analysing the various rock samples will allow them to draw conclusions as to why the two sides of the moon differ so clearly from one another. For example, they differ significantly from each other in terms of topography, the thickness of the upper rock crust, the distribution of basalts and the thorium concentration in the deposits. The samples analysed are some of the youngest and oldest volcanic rocks on the moon that have been identified to date. The older material has significantly higher concentrations of potassium, phosphorus and rare earths compared to the younger samples; they therefore probably originate from different magma sources.
Spectrum of Science
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Original article on Spektrum.de
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