China’s historic lunar lander Chang’e-4 has helped reveal important information on how the moon may have evolved.
The last time we heard from the Chang’e-4, Chinese scientists were mourning the loss of a cotton plant they had attempted to grow in the lander on the surface of the moon. Now however, the Chinese Academy of Sciences has revealed new information from within one of the largest craters in the solar system.
The South Pole-Aitken basin stretches 2,500km across, or half the width of China itself. Since the 1970s, a theory has emerged that in the moon’s infancy, an ocean of magma covered the surface of the moon. As this began to cool, lighter materials floated to the top, leaving heavier material to sink deeper.
As the top crusted over, it created a sheet of mare basalt that encased a mantle of dense materials such as olivine and pyroxene. When asteroids and other space junk collided with the moon, pieces of this lunar mantle were thrown up to the surface.
Researchers working with the lander’s data expected to find a wealth of mantle material on the floor of the basin where Chang’e-4 landed, but were surprised to find only mere traces of olivine, the primary component of Earth’s upper mantle.
“The absence of abundant olivine in the [basin] interior remains a conundrum,” said Li Chunlai, a professor of the National Astronomical Observatories of Chinese Academy of Sciences. “Could the predictions of an olivine-rich lunar mantle be incorrect?”
As it turns out, olivine was found in more abundance in samples from deeper impacts. A new theory proposed by Li and the researchers is that rather than the mantle being dominated by either olivine or pyroxene, both share an equal presence.
Such discoveries are important, Li said, in helping us understand more about Earth’s satellite, the place NASA and other space agencies are hoping to colonise in just a few years’ time.
“Understanding the composition of the lunar mantle is critical for testing whether a magma ocean ever existed, as postulated,” he said. “It also helps advance our understanding of the thermal and magmatic evolution of the moon.”
Details of the findings have been published to Nature.