Billions of neutrinos, an elusive species of subatomic particles, pass through our bodies and the entire Earth each second. But experiments to find neutrinos requires new ways of cleaning up the sensitive measurements.
The most recent ally in this quest seems to come from archaeology: lead from a Roman ship which sank 2000 years ago could be ideal for capturing neutrinos from distant exploding stars.
The RES-NOVA research team, set on catching neutrinos coming from the cores of supernovae, turned to ancient mineral to improve its experimental signal. A few of the passing neutrinos will be caught by colliding with atomic nuclei, making lead the material of choice thanks to its heavy nucleus.
Radioactivity is an important consideration though. Scientists design crystals with lead in order to detect neutrinos. Newly mined lead contains traces of radioactive elements which begin to cool down only after processing, and this radioactivity affects these measurements.
But if the lead was processed a long time ago, say during the Roman empire, the natural radioactivity has largely settled down by now. And this is how the wreck of a ship loaded with the mineral, sunk off Sardinia around 50 BCE, provided lead with ten thousand less radioactivity than newer lead.
The ship was discovered in 1988 but its load was too costly to retrieve. The expedition was eventually funded by Italy's National Institute for Nuclear Physics, or INFN, in exchange for a few tons of this VIP metal.
Part of it has already been used in experiments as a shield against ambient radiation. The proposal of RES-NOVA (Latin for “new thing”) is novel though: here the lead will be a component of the crystals with which the neutrinos from outer space will actually collide. The low-radioactivity crystals are expected to be more sensitive in detecting neutrinos and thus to study more distant supernovae, covering the whole bulk of the Milky Way.
In the process, ancient lead, probably initially destined to become ammunition, will be given a second life as an explorer of stars.
Correction: This story was updated to clarify the role of low-radioactivity lead in crystals