Evidence of volcanic processes discovered on the dark side of the Moon

Apollo16 Sun

The Moon is a world with little activity. It is constantly bombarded by micrometeoroids and the occasional larger object. Beyond that there are no major events. Unlike its past, when it is believed to have presented a great volcanism on its entire surface. It had a large lava cover that forged what we now know as seas. Recently, a team using data from two Chinese probes managed to find evidence of new volcanic processes on the Moon.

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False-color map of the temperature difference centered on the temperature anomaly on the far side of the Moon.

Explored the Moon

China has a space program that has continuously explored the Moon for the past decade. It has orbiters, rovers and sample recovery missions. The first two, Chang'e 1 and 2, sought to lay the first steps of lunar conquest. These had instruments to study our satellite, as well as to demonstrate and test the country's industry and technology.

The Chinese space program is largely carried out under a great curtain that prevents the world from knowing the progress, news or problems they encounter. However, a considerable portion of the data that are collected are released to the public for independent review. Thus, a team of researchers took advantage of microwave remote sensing data to analyze the changes in the surface between day and night.

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Orbital photograph taken by NASA's Ebb probe of the Compton-Belkovich anomaly on the far side of the Moon.

Evidence of volcanic activity

Microwaves, whose wavelength is longer than infrared, are used to measure temperatures below the surface. By combining the data from all the sweeps made by the Chang'e 1 and 2 probes, maps of the thermal evolution of the Moon can be created.

On the far side is a volcanic complex known as Compton-Belkovich, so called because it lies between the two craters bearing those names, which has generated great curiosity among researchers since 1998. When using a gamma ray detector, a temperature anomaly appeared. Likewise, it glowed brightly at microwave wavelengths. Indicating an intense heat source that lurked beneath the surface, hidden deep within the lunar crust.

Compton Belkovich Thorium Anomaly
Location of the Compton-Belkovich anomaly.

When the outer layer of the volcano is analyzed, there is strong evidence that the last eruption occurred more than three and a half billion years ago, so the heat source must have been something other than molten magma. The only other possibility is a large concentration of radioactive material, specifically thorium.

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Diagram of the granitic batholith hidden several kilometers deep in the Compton-Belkovich volcanic complex. The colors represent the heat flow produced by radioactive elements.

Secrets beneath the surface

There is only one kind of rock capable of accounting for the amount of thorium present inside the volcano. The so-called granitic batholithsThe lava flows, more than 20 kilometers in diameter, are large quantities of trapped lava that cannot escape before cooling. Reaching low temperatures gives way to granite, a rock commonly found beneath the earth's mountain ranges and which has high concentrations of radioactive elements. However, this is the first time that detected on a body other than the Earth.

The interior of the Moon remains a great mystery. Its study is limited to analyses of its surface and measurements of seismic activity, however, these leave large gaps in the possible structures hiding several kilometers deep. Which will only be discovered if the space agencies release the information collected and everyone has the ability to analyze it and unveil the secrets of the solar system.

Francisco Andrés Forero Daza