Humans have been practicing the art of glass-making for almost 4,000 years, but nature has been doing it for billions of years. If glass is left out in the open for eons, it could undergo drastic changes, especially with no air and running water. Scientists try to understand these changes by studying naturally occurring glass on the moon's surface.
Glass on the Lunar Surface
The moon may not seem to be a prominent place to find glass samples since it is known that rock chips and other loose materials cover its surface. However, previous research has shown that the lunar surfaces are littered with tiny bits of glass subjected to cosmic rays and radiation from the Sun.
As meteoroids constantly hit the lunar surface, they bombard the regolith, melting them into tiny pools. As the molten layer of unconsolidated rocky materials cools back down, it hardens to form pieces of glass.
Even on the moon, glass does not last for long without undergoing crucial changes. Although the moon has neither a significant atmosphere nor running water to weather rocks like on our planet, its surface is subject to radiation, which the Earth's atmosphere can filter out. Some of this radiation comes from the Sun, while some arrive as cosmic rays from farther regions. Regardless of the radiation source, its effect on the moon builds up after billions of years of exposure.
Effect of Prolonged Radiation
Materials scientists at Songshan Lake Materials Laboratory wanted to investigate how the moon's glass is affected by the bombardment of cosmic rays and solar radiation. In collaboration with experts from the China Academy of Space Technology and the Chinese Academy of Sciences, the researchers studied glass made naturally on the moon by meteoroids striking and melting lunar regolith.
In this study, the experts obtained five tiny bits of glass brought back by the Chang'e-5 moon lander. Each piece, which is no bigger than the width of a human hair, was studied using the transmission electron microscope, giving the researchers a view of its structure.
The team also squeezed each sample to observe their reaction to force. Both methods used in the study gave the scientists a baseline to understand how aging has affected the bits of lunar glass.
For approximately five minutes, each glass sample was also subjected to extreme heat that reached 650 degrees Celsius. The heat treatment was enough to melt the glass and bring the samples back to their original form. By doing so, the researchers could compare the lunar glass's original form with their current state. This way, the team can observe what billions of years of radiation exposure has done to the glass.
After observing the differences, the experts discovered major changes in Young's modulus, a measure of the force a material can take before it gets distorted. The change was found to be as much as 70%. Additionally, the research team discovered that the radiation bombardment had made the lunar glass harder.
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