  We present a novel experimental concept to search for proton decay. Using
paleo-detectors, ancient minerals acquired from deep underground which can hold
traces of charged particles, it may be possible to conduct a search for $p \to
\bar{\nu} K^+$ via the track produced at the endpoint of the kaon. Such a
search is not possible on Earth due to large atmospheric-neutrino-induced
backgrounds. However, the Moon offers a reprieve from this background, since
the conventional component of the cosmic-ray-induced neutrino flux at the Moon
is significantly suppressed due to the Moon's lack of atmosphere. For a 100 g,
$10^9$ year old (100 kton$\cdot$year exposure) sample of olivine extracted from
the Moon, we expect about 0.5 kaon endpoints due to neutrino backgrounds,
including secondary interactions. If such a lunar paleo-detector sample can be
acquired and efficiently analyzed, proton decay sensitivity exceeding
$\tau_p\sim10^{34}$ years may be achieved, competitive with Super-Kamiokande's
current published limit ($\tau_p>5.9\times 10^{33}$ years at 90% CL) and the
projected reach of DUNE and Hyper-Kamiokande in the $p \to \bar{\nu} K^+$
channel. This concept is clearly futuristic, not least since it relies on
extracting mineral samples from a few kilometers below the surface of the Moon
and then efficiently scanning them for kaon endpoint induced crystal defects
with sub-micron-scale resolution. However, the search for proton decay is in
urgent need of a paradigm shift, and paleo-detectors could provide a promising
alternative to conventional experiments.
