China’s ambitious Chang’e-6 mission has delivered new insights into the Moon’s geological past, particularly the differences between its near and far sides.
Launched on May 3, 2024 the mission returned with 1,935.3 grams of lunar material from the South Pole–Aitken Basin (SPA) on the Moon’s far side, arriving back on Earth on 25 June 2024.
These samples have enabled scientists to explore one of planetary science’s long-standing mysteries regarding the Moon’s topographical and compositional asymmetry.
The SPA, the largest and oldest impact structure on the Moon, was formed approximately 4.25 billion years ago by a massive impact. This event is thought to have released energy equivalent to that of a trillion atomic bombs.
Until recently, the impact’s effects on lunar geology and thermal evolution remained unsolved, but recent studies have begun to unravel these mysteries.
Research conducted over the past year by teams from CAS institutions, including the Institute of Geology and Geophysics (IGG) and the National Astronomical Observatories (NAOC), has led to four significant discoveries.
These findings were published in the journal Nature, marking a major step forward in understanding the lunar landscape. According to Prof. WU Fuyuan, “the geological consequences of the impact that formed the SPA are, for the first time, revealed collectively in these four Nature papers.”
One key discovery is the evidence of prolonged volcanic activity on the Moon’s far side. The analysis identified two distinct volcanic phases occurring 4.2 billion and 2.8 billion years ago.
This persistence of volcanic activity for at least 1.4 billion years is far longer than previously believed.
Additionally, a fluctuating magnetic field was observed. Measurements revealed a resurgence in the Moon’s magnetic field around 2.8 billion years ago, indicating that the lunar dynamo responsible for generating magnetic fields was more active than previously thought, experiencing episodes of fluctuation rather than a steady decline.
The samples also highlight an asymmetric water distribution between the Moon’s near and far sides.
The far side’s mantle contains significantly less water, suggesting an uneven distribution of volatile elements within the lunar interior, shedding light on the Moon’s compositional diversity.
Finally, geochemical analyses of the basalt samples unveiled a mantle source described as “ultra-depleted,” pointing to a primordial depleted mantle or massive melt extraction due to large impacts. This insight points to the role of major impacts in shaping the Moon’s interior.
These findings not only illuminate the evolution of the Moon’s far side but also shows the transformative impact of the Chang’e-6 mission, offering a critical reference point for studying early Solar System impacts.
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