Crystalline Lunar Spherules

It’s a harsh place, the surface of the moon. NWA 8010 is a lunar regolith breccia meteorite that bears witness to this.

Melt veins are formed by large impacts. The veins in NWA 8010 did not cool instantly into glass. They had time to nucleate along wall rock and crystallize into feathery tufts of very fine laths that grew to meet in the center of the veins.

Apollo 14 and 16 returned with crystalline lunar spherules similar to those in NWA 8010. Researchers believe a large impact was necessary to form not only melt droplets but also a cloud of dust and gas that insulated the molten material from the cold of space and allowed time for crystals to form. Long flight time is inferred by the time needed for solidification and, in the case of Apollo 14, the composition of the spherules differs from the rock in which they are found.

All these photos were taken from the single thin section shown last.

A one millimeter thick melt vein runs between the left and right edges of this 4.5 mm wide view. Fine crystalline laths grew in bundles from the edges of the melt inwardly toward the center of the vein. Cross-polarized light. NWA 8010 Lunar (feldspathic breccia).

Large chondrule-like spherule. Apparent length is 0.9 mm (900 μm).  XPL.  NWA 8010 Lunar (feldspathic breccia).

A pair of lunar crystalline spherules. Diameters are 200 μm and 65 μm. Plane polarized light. NWA 8010 Lunar (feldspathic breccia).

Plane polarized light. Plane polarized light.

Two lunar crystalline spherules. The smaller is 240 μm in diameter. The larger has two lithologies. The core is 170 μm in diameter and the overall spherule has an length of 370 μm. PPL. NWA 8010 Lunar (feldspathic breccia).

Partial lunar crystalline spherule 90 μm in diameter. PPL. NWA 8010 Lunar (feldspathic breccia).

Lunar crystalline spherule 80 μm in diameter. PPL. NWA 8010 Lunar (feldspathic breccia).

Dark lunar crystalline spherule 60 μm in diameter. What is the small red spherule? A glassy impact droplet? Red volcanic fire fountain glass? PPL. NWA 8010 Lunar (feldspathic breccia).

Sample thin section, 15 mm wide. Transmitted white light. NWA 8010 Lunar (feldspathic breccia).

About the Author

John is a natural history enthusiast living in Oregon.

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