Ion Probes Unpack a 4.3-Billion-Year-Old Lunar Mystery
By analyzing impact-melt fragments from Chang'e-6 soil samples using a domestically developed ion probe, the team linked surface disparities to the massive South Pole-Aitken Basin impact approximately 4.3 billion years ago.
When viewed from Earth, the near side is dominated by dark, basaltic volcanic plains known as maria. Conversely, the far side is defined by rugged, heavily cratered highlands stripped of extensive volcanic flooding.
Precision Mass Spectrometry on Chang’e-6 Regolith
To investigate this divergence, scientists turned to material returned by China’s historic 2024 lunar mission. According to Long Tao, deputy director of the Center for Planetary Sciences, researchers utilized a homegrown ion probe to target microscale impact-melt fragments extracted from the regolith.
The instrument fires an ion beam with pinpoint accuracy, comparable to sinking a basketball from 3,000 meters away, vaporizing tiny target areas to generate secondary ions for ultra-precise mass spectrometry.
The Cataclysmic Formation of the South Pole-Aitken Basin
Analytical data point directly to a colossal cataclysm. The formation of the South Pole-Aitken Basin—recognized as the largest, deepest, and oldest impact structure on the Moon—set the stage for the planet’s dual personality.
According to research team member Che Xiaochao, the monumental kinetic event deposited radioactive elements across specific regions, fundamentally altering the thermal and geological evolution of the impacted hemisphere.
Bringing 1,935.3 Grams of Far-Side History Back to Earth
In 2024, the Chang’e-6 mission touched down in this ancient basin, successfully scooping up 1,935.3 grams of lunar material from the far side. This payload marked a historic engineering and scientific milestone, representing the first time physical samples from the lunar far side were successfully brought back to Earth for laboratory-grade analysis.
Radioactive Isotope Gradients and Volcanic Asymmetry
The far-side samples exhibit distinctly higher concentrations of radioactive isotopes compared to primordial crustal samples that escaped the ancient basin-forming shock.
