  We present HST/WFC3 multiband imagery of N103B, the remnant of a Type Ia
supernova in the Large Magellanic Cloud, as well as HST/COS ultraviolet
spectroscopy of the brightest radiatively shocked region. The images show a
wide range of morphology and relative emission-line intensities, from smooth
Balmer-line dominated collisionless shocks due to the primary blast wave, to
clumpy radiative shock filaments due to secondary shocks in density
enhancements. The COS data show strong FUV line emission despite a moderately
high extinction along this line of sight. We use the COS data with previous
optical spectra to constrain the shock conditions and refine the abundance
analysis, finding abundances typical of the local interstellar medium within
the uncertainties. Under an assumption that the material being shocked was shed
from the pre-supernova system, this finding places constraints on any
significant enrichment in that material, and thus on the non-degenerate star in
what was presumably a single-degenerate Type Ia supernova.
