  We derive purely gravitational constraints on dark matter and cosmic neutrino
profiles in the solar system using asteroid (101955) Bennu. We focus on Bennu
because of its extensive tracking data and high-fidelity trajectory modeling
resulting from the OSIRIS-REx mission. We find that the local density of dark
matter is bound by $\rho_{\rm DM}\lesssim 3.3\times 10^{-15}\;\rm kg/m^3 \simeq
6\times10^6\,\bar{\rho}_{\rm DM}$, in the vicinity of $\sim 1.1$ au (where
$\bar{\rho}_{\rm DM}\simeq 0.3\;\rm GeV/cm^3$). We show that high-precision
tracking data of solar system objects can constrain cosmic neutrino
overdensities relative to the Standard Model prediction $\bar{n}_{\nu}$, at the
level of $\eta\equiv n_\nu/\bar{n}_{\nu}\lesssim 1.7 \times 10^{11}(0.1 \;{\rm
eV}/m_\nu)$ (Saturn), comparable to the existing bounds from KATRIN and other
previous laboratory experiments (with $m_\nu$ the neutrino mass). These local
bounds have interesting implications for existing and future direct-detection
experiments. Our constraints apply to all dark matter candidates but are
particularly meaningful for scenarios including solar halos, stellar basins,
and axion miniclusters, which predict or allow overdensities in the solar
system. Furthermore, introducing a DM-SM long-range fifth force with a strength
$\tilde{\alpha}_D$ times stronger than gravity, Bennu can set a constraint on
$\rho_{\rm DM}\lesssim \bar{\rho}_{\rm DM}\left(6 \times
10^6/\tilde{\alpha}_D\right)$. These constraints can be improved in the future
as the accuracy of tracking data improves, observational arcs increase, and
more missions visit asteroids.
