  Context. Airless planetary objects have their surfaces covered by craters,
and these can be used to study the characteristics of asteroid populations.
Planetary surfaces present binary craters that are associated with the
synchronous impact of binary asteroids. Aims. We identify binary craters on
asteroids (1) Ceres and (4) Vesta, and aim to characterize the properties (size
ratio and orbital plane) of the binary asteroids that might have formed them.
Methods. We used global crater databases developed in previous studies and
mosaics of images from the NASA DAWN mission high-altitude and low-altitude
mapping orbits. We established selection criteria to identify craters that were
most likely a product of the impact of a binary asteroid. We performed
numerical simulations to predict the orientation of the binary craters assuming
the population of impactors has mutual orbits coplanar with heliocentric
orbits, as the current census of binary asteroids suggests. We compared our
simulations with our survey of binary craters on Ceres and Vesta through a
Kolmogorov-Smirnov test. Results. We find geomorphological evidence of 39 and
18 synchronous impacts on the surfaces of Ceres and Vesta, respectively. The
associated binary asteroids are widely separated and similar in diameter. The
distributions of the orientation of these binary craters on both bodies are
statistically different from numerical impact simulations that assume binary
asteroids with coplanar mutual and heliocentric orbits. Conclusions. Although
the identification of binary craters on both bodies and the sample size are
limited, these findings are consistent with a population of well-separated and
similarly sized binary asteroids with nonzero obliquity that remains to be
observed, in agreement with the population of binary craters identified on
Mars.
