Researchers, including scientists from Curtin University, have analysed some of the first rock samples ever returned from the moon’s far side, uncovering evidence that challenges one of planetary science’s longest-standing theories about the early history of the solar system.
The study examined tiny fragments of impact-melt rock collected by China’s Chang’e-6 mission from the South Pole–Aitken Basin, the largest and oldest known impact crater on the moon. By dating the rocks, researchers reconstructed more than 3 billion years of asteroid impacts, finding the bombardment of the moon declined steadily over time rather than occurring in a short-lived period of intense collisions known as the Late Heavy Bombardment.
The findings carry implications far beyond the moon. Unlike Earth, where erosion, volcanic activity and plate tectonics have erased much of the geological record from the planet’s earliest history, the moon has preserved a largely intact archive of events dating back more than 4 billion years.
That makes lunar rocks an invaluable record of the conditions that also shaped the young Earth.
According to the research team, analysing samples from the moon’s far side has provided an unprecedented opportunity to compare two geologically distinct hemispheres for the first time.
Previous laboratory studies had relied almost entirely on material collected from the near side during the Apollo and Soviet Luna missions, leaving scientists with an incomplete picture of the moon’s evolution.
The far side’s comparatively undisturbed geology has preserved a cleaner record of ancient impacts, allowing researchers to identify impact events spanning from around 4.33 billion to 1.13 billion years ago.
Those observations suggest the early solar system experienced a prolonged decline in asteroid collisions rather than a brief, catastrophic spike, prompting scientists to reconsider existing models of planetary evolution.
The research also offers fresh insight into the conditions that may have influenced the emergence of life on Earth. Because the Earth and moon formed together and occupied the same region of the solar system, the impacts recorded on the moon provide an indirect record of the environment experienced by the young Earth during its formative years.
The findings highlight the growing scientific value of international lunar exploration missions. China’s Chang’e-6 mission became the first to successfully return samples from the moon’s far side, opening an entirely new chapter in planetary science and providing researchers with access to material that had never before been available for laboratory analysis.
Published in Science Advances, the research reinforces Australia’s growing contribution to international planetary science through Curtin University’s expertise in geochronology and planetary geology.
As a new era of lunar exploration gathers pace, scientists expect future sample return missions to further refine humanity’s understanding of how the moon, Earth and the wider solar system evolved billions of years ago.
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