  The Mission Accessible Near-Earth Object Survey (MANOS) aims to observe and
characterize small (mean absolute magnitude H ~ 25 mag) Near-Earth Objects
(NEOs) that are accessible by spacecraft (mean $\Delta v$ ~ 5.7 km/s) and that
make close approaches with the Earth (mean Minimum Orbital Intersection
Distance MOID ~ 0.03 AU). We present here the first results of the MANOS
visible spectroscopic survey. The spectra were obtained from August 2013 to
March 2018 at Lowell Observatory's Discovery Channel 4.3 meter telescope, and
both Gemini North and South facilities. In total, 210 NEOs have been observed
and taxonomically classified. Our taxonomic distribution shows significant
variations with respect to surveys of larger objects. We suspect these to be
due to a dependence of Main Belt source regions on object size. Compared to
previous surveys of larger objects (Binzel et al. 2019, 2004; Perna et al.
2018), we report a lower fraction of S+Q-complex asteroids of 43.8 $\pm$ 4.6%.
We associate this decrease with a lack of Phocaea family members at very small
size. We also report higher fractions of X-complex and A-type asteroids of 23.8
$\pm$ 3.3% and 3.8 $\pm$ 1.3% respectively due to an increase of Hungaria
family objects at small size. We find a strong correlation between the Q/S
ratio and perihelion distance. We suggest this correlation is due to planetary
close encounters with Venus playing a major role in turning asteroids from S to
Q-type. This hypothesis is supported by a similar correlation between the Q/S
ratio and Venus MOID.
