Tiny particles of iron trapped inside lunar glass may preserve evidence of the Moon’s ancient magnetic history. Scientists studying soil returned by China’s Chang’e-6 mission have identified face-centered cubic γ-Fe, an unusual form of metallic iron never before confirmed in natural lunar samples.
The discovery is particularly unexpected because γ-Fe normally exists only at high temperatures and changes into a different crystal structure as it cools. Yet researchers found that this phase of iron had survived inside microscopic glass particles formed during impacts on the lunar surface.
Researchers led by Prof. Haifeng Du of the High Magnetic Field Laboratory at the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS) examined impact glass containing numerous nanoscale iron particles. Using focused ion beam preparation, transmission electron microscopy, and chemical analysis, they confirmed that γ-Fe was the dominant iron phase in the two glass samples studied. Their findings were published September 16 in the Proceedings of the National Academy of Sciences (PNAS).
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