Groundbreaking Discovery

In a groundbreaking discovery, Chinese scientists have unveiled that the Moon's largest and oldest impact crater, known as the South Pole-Aitken (SPA) Basin, was formed approximately 4.25 billion years ago. This revelation, stemming from lunar soil samples collected by the Chang'e-6 mission, marks a pivotal moment in the study of both lunar evolution and the history of our solar system.

Significance of the Discovery

Published in the academic journal National Science Review, this significant finding provides a crucial reference point for understanding large impact events in the solar system's formative years. With a staggering diameter of about 2,500 kilometers, the SPA Basin serves as a monumental record of the Moon's tumultuous history and bears witness to the violent collisions that shaped it.

Benchmark for Impact Events

The formation of the SPA Basin is not only a landmark in lunar history but also a key benchmark for calculating the age of impact events across the solar system, aiding scientists in creating a unified chronology for craters on other planetary bodies, including Mars and Mercury. This ancient crater acts as a 'cosmic clock,' helping researchers to piece together the timeline of our celestial neighborhood.

Historical Challenges

Historically, estimating the age of the SPA Basin has remained a formidable challenge. Scientists utilized two primary methods: one based on the analysis of impact crater statistics, suggesting an age between 4.26 billion and over 4.33 billion years, and the other through investigations of lunar meteorite samples, hinting at a global thermal event around 4.35 to 4.33 billion years ago possibly linked to the SPA impact.

The Chang'e-6 Mission

However, previous endeavors had lacked direct samples from the SPA Basin—until the successful landing of the Chang'e-6 probe, which impeccably recovered samples from the Moon's far side. This extraordinary mission not only collected soil from the interior of the SPA Basin but also provided a rare opportunity to gain insight into the crater's formation age.

Analysis of Lunar Soil Samples

The Chang'e-6 lander targeted the Apollo Basin, an area characterized by lunar mare basalt, intercepting a geological layer marked by subsequent impacts and volcanic activity over the last 2.8 billion years. Electrical analysis found that the soil samples comprised a mix of materials from various epochs, revealing nuances of the Moon's history.

Research Findings

In identifying the samples, the research team, led by Chen Yi from the Institute of Geology and Geophysics, meticulously analyzed over 1,600 fragments from the lunar soil. They distinguished 20 significant fragments, characterized as Norites, which turned out to be a previously unclassified type that the researchers named South Pole-Aitken Norites (SPANs).

Dating the Impact Events

By applying a lead isotopic dating technique to small zircon minerals within these fragments, scientists identified two impactful events corresponding to ages of 4.25 and 3.87 billion years. Each of these Norite samples exhibited distinct mineralogical features, suggesting they derived from various layers of the same impact magma pool.

Further Contextualization

To further contextualize these ancient materials, extensive lithological mapping and sourcing were conducted, drawing from an impressive 447 GB of remote sensing data. Ultimately, these investigations confirmed that the 4.25 billion-year-old Norite originated from a unique region within the SPA Basin.

Implications of the Discovery

This monumental discovery underscores that a significant impact event transpired just 320 million years after the formation of the solar system, shaping the Moon's most considerable impact feature. The findings laid the groundwork for lunar impact dating from far-side samples and offered new insights into the early evolution of the Moon.

Clarifying Theories

Furthermore, the research clarified that the previously speculated global thermal event from approximately 4.35 to 4.33 billion years ago is distinct from the SPA impact, providing important data for understanding the Moon's early development and rectifying existing theories about its evolutionary timeline.

Conclusion

As the quest for knowledge about our Moon progresses, this research exemplifies the strides made in lunar science, potentially unlocking even more mysteries of our celestial neighbor. Stay tuned as we delve deeper into the findings of the Chang'e-6 mission and what they reveal about the Moon's ancient impact history!