Chang'e-6 Lunar Samples Chronology Breakthrough: Science Advances Study Revises Moon Impact Crater Model, Challenging Late Heavy Bombardment Hypothesi

Understanding the Chang'e-6 Mission and Its Historic Sample Return

China's Chang'e-6 mission marked a monumental achievement in lunar exploration when it successfully returned 1,935 grams of samples from the Moon's far side in June 2024. Launched on May 3, 2024, the probe landed in the Apollo Basin within the vast South Pole-Aitken (SPA) basin, the Moon's largest and oldest impact feature. This was the first-ever sample return from the lunar farside, providing unprecedented access to materials untouched by previous Apollo and Luna missions, which focused on the nearside. 62 61

These samples include diverse rock types such as basalts and norites, offering insights into the Moon's geological evolution, volcanism, and bombardment history. For researchers in China, this mission underscores the growing prowess of domestic space science programs led by institutions like the Chinese Academy of Sciences (CAS).

The Groundbreaking Science Advances Study

A team of Chinese scientists published a pivotal paper in Science Advances on February 4, 2026, titled "Lunar chronology model with the Chang'e-6 farside samples and implications for the early impact history." Led by researchers from the Institute of Geology and Geophysics, CAS, the study leverages radiometric ages from these samples to refine the lunar cratering chronology function (CF)—a critical tool for dating planetary surfaces via crater counts. 62

The work integrates far-side data with nearside samples from Apollo, Luna, and Chang'e-5 missions, establishing a universal model applicable across the entire Moon. This publication highlights the collaborative efforts of over 20 authors from CAS institutes and universities like Chengdu University. 61

Radiometric Dating: Unlocking Precise Ages from Lunar Rocks

Radiometric dating, particularly the lead-lead (Pb-Pb) method, was applied to minerals like zircons, phosphates, and Zr-rich phases in the Chang'e-6 samples. The local basalts yielded an age of 2,807 ± 3 million years (Ma), confirming late-stage farside volcanism. More remarkably, norite clasts—believed to be impact melt from the SPA basin—dated to 4,247 ± 5 Ma, providing a key anchor for early lunar history. 62

This process involves measuring the decay of uranium to lead in closed isotopic systems, step-by-step: sample preparation isolates minerals, mass spectrometry analyzes ratios, and isochron plots yield ages with uncertainties. These precise dates surpass previous estimates reliant on crater counting alone. 60

• Basalt samples: Represent post-impact volcanism in Apollo Basin.
• Norite clasts: Crystallized from SPA impact melt ~4.25 billion years ago.
• Methodology: High-resolution imaging and buffered crater counting for N(1) densities.

Refining the Lunar Cratering Chronology Function

The cornerstone of planetary geology, the chronology function (CF) relates crater density N(1)—cumulative craters ≥1 km per km²—to absolute time. Previous models, like Neukum's from 1983, used only nearside data. The new CF is N(1, t) = 3.885 × 10⁻¹⁵ (e⁷⋅⁵⁹⁵ᵗ - 1) + 7.377 × 10⁻⁴ t, fitted via nonlinear least-squares to 20+ calibration points including Chang'e-6. 62

This hybrid exponential-linear form captures rapid early decline followed by steady-state impacts. Farside points fall within nearside 95% confidence intervals, validating universality.Read the full study.

Photo by Brett Jordan on Unsplash

Evidence for Uniform Impact Flux Across the Moon

Contrary to assumptions that the nearside was shielded by Earth, crater densities in the Apollo Basin (N(1)=2.08×10⁻³ km⁻² for basalts) and SPA (N(1)=3.69×10⁻¹ km⁻²) match nearside predictions. Lead author Yue Zongyu noted, "This indicates that the impact flux was homogeneous across the entire moon." 59

This symmetry enables reliable age assignments to unsampled regions, revolutionizing lunar mapping. For Chinese planetary scientists at CAS, it affirms the value of far-side exploration.

Challenging the Late Heavy Bombardment Hypothesis

The Late Heavy Bombardment (LHB) posits a spike in impacts ~3.9 billion years ago, inferred from nearside samples and isotopic anomalies. However, the SPA anchor at 4.247 Ga deviates sharply from LHB and "sawtooth" models, supporting smooth decay: impact rate φ(1, t) = 2.951 × 10⁻¹⁴ e⁷⋅⁵⁹⁵ᵗ + 7.377 × 10⁻⁴. 62 48

No evidence for abrupt flux changes; instead, exponential drop pre-3.0 Ga then linear slowdown. This shifts paradigms on solar system dynamics, questioning Nice model instabilities.CAS insights on SPA age.

Implications for Lunar and Solar System Evolution

The revised model dates geologic units older than Neukum's by up to 340 Ma at ~2.6 Ga, refining volcanism timelines and mantle evolution. It constrains impactor populations—likely trans-Neptunian objects—without cataclysmic migration. For Earth-Moon analogs, it informs habitability windows post-accretion.

• Older basalts suggest prolonged farside magmatism.
• Smooth flux aids Mercury, Mars dating.
• Resolves SPA age debates (previously 4.2-4.3 Ga).

Explore planetary science roles at higher-ed research jobs.

Spotlight on Chinese Academic Contributions

Researchers from CAS's Institute of Geology and Geophysics, Aerospace Information Research Institute, and Chengdu University drove this breakthrough. Their expertise in geochronology and remote sensing exemplifies China's rise in space science education. Institutions like these train next-gen experts via programs in planetary geology.China university opportunities.

Photo by Brett Jordan on Unsplash

Future Prospects: Upcoming Missions and Research

Chang'e-7 and -8 will target lunar south pole resources, building on this chronology. International collaborations, including sample sharing, promise further refinements. In China, universities ramp up lunar studies, fostering PhD programs and labs.

Career Pathways in Lunar Science

This discovery opens doors for geologists, astrophysicists, and remote sensing specialists. Chinese higher ed institutions seek talent for space agencies. Check academic CV tips, higher-ed jobs, and rate professors. Postdocs thrive via postdoc positions.