Meteorite’s blue salt points to a long history of space irradiation
Blue salt crystals in the Sidi El Habib 001 meteorite contain optical signatures consistent with radiation-related defects and sodium aggregates. A peer-reviewed mineral study favours space irradiation as an explanation for their colour, while leaving an internal radioactive contribution possible. Noble-gas measurements indicate exposure lasting millions of years, without dating when the salt formed.
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Crystal defects accompany the blue colour
The blue grains inside Sidi El Habib 001, a stony meteorite classified as an ordinary chondrite, contain halite: crystalline sodium chloride. Researchers examined their colour using optical absorption, Raman spectroscopy and elemental measurements. Across 20 optical spectra, they found signatures compatible with radiation-related crystal defects and sodium aggregates. Some weaker spectral assignments remain uncertain. This single peer-reviewed mineral investigation was published in npj Space Exploration.[1]
Low potassium strengthens the external-irradiation explanation
Space irradiation is the researchers’ favoured explanation for the defects. The analysed salt contained relatively little potassium and no clearly identified potassium-chloride inclusions, weakening an explanation based mainly on internal radioactive decay. Nevertheless, a contribution accumulated inside the salt remains possible. Its formation date and subsequent heating history are unknown, preventing a reliable reconstruction of the radioactive exposure before the meteorite left its parent body.[1]
Exposure ages do not date salt formation
Helium indicated exposure for 3.9 million years; the neon estimate was 4.3 million years and argon gave 2.6 million years. Their disagreement leaves the detailed exposure history unresolved; these measurements do not establish when halite crystallised. Earlier mineral relationships support a fluid-related origin for the salt, followed by irradiation. No clear fluid inclusions were identified in the analysed areas, so the colour investigation supplies no direct measurement of an ancient trapped fluid.[1]
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