summary - Direct experimental search for strangelets (hypothetical stable lumps of strange quark matter) in lunar soil, using the Yale Wright Nuclear Structure Laboratory accelerator as a mass spectrometer to look for anomalously heavy isotopes at nuclear charge Z=8 (oxygen-like). Finds no strangelet candidates and sets a 95%-confidence upper limit on strangelet concentration in lunar soil of about 10^-16 per nucleon for that charge, exploiting the Moon’s airless, multi-billion-year-exposed surface as a natural collector for any strangelet flux reaching it.
relevance_note - A direct empirical search bounding strangelet abundance/flux - independent of, and complementary to, the cosmic-ray-collision-survival argument, since it constrains whether strangelets exist/persist at all rather than whether producing them in a collider would be dangerous.