  Recent surveys have discovered a population of faint supernovae, known as
Ca-rich gap transients, inferred to originate from explosive ignitions of white
dwarfs. In addition to their unique spectra and luminosities, these supernovae
have an unusual spatial distribution and are predominantly found at large
distances from their presumed host galaxies. We show that the locations of
Ca-rich gap transients are well matched to the distribution of dwarf spheroidal
galaxies surrounding large galaxies, in accordance with a scenario where dark
matter interactions induce thermonuclear explosions among low-mass white dwarfs
that may be otherwise difficult to ignite with standard stellar or binary
evolution mechanisms. A plausible candidate to explain the observed event rate
are primordial black holes with masses above $10^{21}$ grams.
