Surface microstructures of lunar soil reveal an intermediate stage in space weathering process

A research performed by a joint group from Chinese language Academy of Sciences used aberration-corrected transmission electron microscopy (TEM), Electron-energy loss spectroscopy (EELS) and scanning transmission electron microscopy (STEM) to look at the microstructures and chemical compositions at nano/atomic scales of 25 soil grains (1-3 μm in dimension) from lunar pattern CE5C0400YJFM00507 (1.5 g).

The soil primarily contains the minerals olivine, pyroxene, anorthite and glass beads. To keep away from attainable chemical contamination and ion-bombing-induced amorphization, the group didn’t make use of the targeted ion beam (FIB) to chop the majority samples aside from the glass bead.

First, they unambiguously recognized the wüstite FeO nanoparticles as an alternative of npFe⁰ which are embedded in amorphous Si_xO_y rims exterior the olivine grains. This distinctive rim construction has not been reported for every other lunar, terrestrial, Martian, or meteorite samples to this point.

Provided that the nano-phase Fe is the ultimate product of decomposing olivine Fe₂SiO₄, they recommend that wüstite FeO could function an intermediate state of the thermal decomposition course of, after which the FeO could additional remodel into nano-phase Fe within the presence of cosmic radiation or solar flares.

For pyroxene and anorthite, the chemical compositions of floor areas are equivalent to inside elements, and there’s no Si_xO_y rim exterior pattern. In the meantime, no overseas risky parts deposition layer and solar flare tracks will be discovered on the floor or contained in the olivine and different minerals.

Such findings suggest that the studied samples don’t endure extreme space weathering, and the underlying mechanism deserves additional investigation. They supply clues or constraints on the incipient formation mechanism of rim construction beneath space weathering.

The analysis was revealed in Science Bulletin.