  In Newtonian gravity, mass is an intrinsic property of matter while in
general relativity (GR), mass is a contextual property of matter, i.e., matter
can simultaneously possess two different values of mass when it is responsible
for two different spatiotemporal geometries. Herein, we explore the possibility
that the astrophysical missing mass attributed to non-baryonic dark matter (DM)
actually obtains because we have been assuming the Newtonian view of mass
rather than the GR view. Since an exact GR solution for realistic astrophysical
situations is not feasible, we explore GR-motivated ansatzes relating proper
mass and dynamic mass for one and the same baryonic matter, as justified by GR
contextuality. We consider four GR alternatives and find that the GR ansatz
motivated by metric perturbation theory works well in fitting galactic rotation
curves (THINGS data), the mass profiles of X-ray clusters (ROSAT and ASCA data)
and the angular power spectrum of the cosmic microwave background (CMB, Planck
2015 data) without DM. We compare our galactic rotation curve fits to modified
Newtonian dynamics (MOND), Burkett halo DM and Navarro-Frenk-White (NFW) halo
DM. We compare our X-ray cluster mass profile fits to metric skew-tensor
gravity (MSTG) and core-modified NFW DM. We compare our CMB angular power
spectrum fit to scalar-tensor-vector gravity (STVG) and $\Lambda$CDM. Overall,
we find our fits to be comparable to those of MOND, MSTG, STVG, $\Lambda$CDM,
Burkett, and NFW. We present and discuss correlations and trends for the best
fit values of our fitting parameters. For the most part, the correlations are
consistent with well-established results at all scales, which is perhaps
surprising given the simple functional form of the GR ansatz.
