Ancient shipwreck to aid ghostly neutrino search

Old underwater lead

By Jennifer Ouellette - Discovery News

You wouldn't think a sunken ship from 2000 years ago could hold the key to the success of a neutrino detection experiment, except perhaps in a Hollywood movie, or a NOVA special on Jacques Cousteau. But sometimes truth really is stranger than fiction.

Scientists with the Cryogenic Underground Observatory for Rare Events (CUORE), a neutrino observatory buried under the Gran Sasso mountain in Italy, hit the mother load when archaeologists discovered a Spanish ship off the coast of Sardinia, filled with lead that dates back two millennia.

Yes, lead. Really, really old lead. That might not seem very exciting to you, but for CUORE scientists, it's a godsend. They use lead (also copper) as a shielding material for their neutrino detection materials.

See, neutrinos -- dubbed "ghost particles" because they so rarely interact with everything (billions course through you every second) -- are extremely difficult to detect, in part because their signals can be obscured by things like cosmic rays, and the natural radioactivity in rocks, for example.

CUORE is looking for an even rarer event, known as neutrinoless double-beta decay. Among other things, such an observation would provide a handy means of directly calculating the mass of a neutrino (which is very, very small -- so small that for decades physicists believed neutrinos had no mass).

Alas, there are also trace amounts of radioactivity in the very materials that are supposed to shield the experiments from interference -- the radioactive isotope lead-210, in the case of contemporary lead ingots.

But if you have lead that is 2000 years old, that radioactive isotope has pretty much disappeared.

Unfortunately, lead that old is quite a rare find. US scientists working on the IGEX experiment lucked out a few years ago when they snagged from 450-year-old lead from a sunken Spanish galleon.

NOVA Jacques Cousteau neutrinos lead ingots Cryogenic Underground Observatory for Rare Events Spanish ship Sardinia