  Comet 107P/Wilson-Harrington, cross-listed as asteroid 4015, is one of the
original transition objects whose properties do not neatly fit into a cometary
or asteroidal origin. Discovered in a period of apparently gas-dominated
activity in 1949, it was subsequently lost and recovered as the inactive
asteroid 1979 VA. We obtained new and re-analyzed archival observations of the
object, compared to meteorites, and conducted new orbital integrations in order
to understand the nature of this object and to understand where it falls on the
asteroid-comet continuum. Wilson-Harrington's reflectance spectrum is
approximately neutral from visible to near-infrared wavelengths, but has a
reflectance maximum near 0.8-0.9 microns. The object's spectrum is well matched
by laboratory spectra of carbonaceous chondrite meteorites like the CM
Murchison or the CI Ivuna. The object's phase curve is compatible with either
an asteroidal or cometary origin, and its recent orbital history has no periods
with high enough temperatures to have altered its surface. While it is possible
that some unknown process has acted to change the surface from an originally
cometary one, we instead prefer a fundamentally asteroidal origin for
Wilson-Harrington which can explain its surface and orbital properties.
However, this would require a way to maintain significant (hyper-)volatile
supplies on the near-Earth objects beyond what is currently expected.
Wilson-Harrington's similar meteorite affinity and possible orbital link to
sample return targets (162173) Ryugu and (101955) Bennu suggest that the
returned samples from the Hayabusa-2 and OSIRIS-REx missions might hold the key
to understanding this object.
