  The surfaces of airless bodies such as asteroids are exposed to many
phenomena that can alter their physical properties. Bennu, the target of the
OSIRIS-REx mission, has demonstrated how complex the surface of a small body
can be. In 2019 November, the potentially hazardous asteroid 2015 JD1
experienced a close approach of 0.0331 au from the Earth. We present results of
the physical characterization of 2015 JD1 based on ground-based radar,
spectroscopy, and photometric observations acquired during 2019 November. Radar
polarimetry measurements from the Arecibo Observatory indicate a
morphologically complex surface. The delay-Doppler images reveal a
contact-binary asteroid with an estimated visible extent of ~150 m. Our
observations suggest that 2015 JD1 is an E-type asteroid with a surface
composition similar to aubrites, a class of differentiated enstatite
meteorites. The dynamical properties of 2015 JD1 suggest it came from the
$\nu_6$ resonance with Jupiter, and spectral comparison with major E-type
bodies suggest that it may have been derived from a parental body similar to
the progenitor of the E-type (64) Angelina. Significantly, we find rotational
spectral variation across the surface of 2015 JD1 from red to blue spectral
slope. Our compositional analysis suggests that the spectral slope variation
could be due to the lack of iron and sulfides in one area of the 2015 JD1
and/or differences in grain sizes.
