  Using the Moon to occult the Sun, the Clementine spacecraft used its
navigation cameras to map the inner zodiacal light at optical wavelengths over
elongations of 3-30 degrees from the Sun. This surface brightness map is then
used to infer the spatial distribution of interplanetary dust over heliocentric
distances of about 10 solar radii to the orbit of Venus. We also apply a simple
model that attributes the zodiacal light as being due to three dust populations
having distinct inclination distributions, namely, dust from asteroids and
Jupiter-family comets (JFCs), dust from Halley-type comets, and an isotropic
cloud of dust from Oort Cloud comets. The best-fitting scenario indicates that
asteroids + JFCs are the source of about 45% of the optical dust cross-section
seen in the ecliptic at 1 AU, but that at least 89% of the dust cross-section
enclosed by a 1 AU radius sphere is of a cometary origin. When these results
are extrapolated out to the asteroid belt, we find an upper limit on the mass
of the light-reflecting asteroidal dust that is equivalent to a 12 km asteroid,
and a similar extrapolation of the isotropic dust cloud out to Oort Cloud
distances yields a mass equivalent to a 30 km comet, although the latter mass
is uncertain by orders of magnitude.
