  Using the multi-band imager MapCam onboard the OSIRIS-REx (Origins, Spectral
Interpretation, Resource Identification, and Security-Regolith Explorer)
spacecraft, we identified 77 instances of proposed exogenic materials
distributed globally on the surface of the B-type asteroid (101955) Bennu. We
identified materials as exogenic on the basis of an absorption near 1 um that
is indicative of anhydrous silicates. The exogenic materials are spatially
resolved by the telescopic camera PolyCam. All such materials are brighter than
their surroundings, and they are expressed in a variety of morphologies:
homogeneous, breccia-like, inclusion-like, and others. Inclusion-like features
are the most common. Visible spectrophotometry was obtained for 46 of the 77
locations from MapCam images. Principal component analysis indicates at least
two trends: (i) mixing of Bennu's average spectrum with a strong 1-um band
absorption, possibly from pyroxene-rich material, and (ii) mixing with a weak
1-um band absorption. The endmember with a strong 1-um feature is consistent
with Howardite-Eucrite-Diogenite (HED) meteorites, whereas the one showing a
weak 1-um feature may be consistent with HEDs, ordinary chondrites, or
carbonaceous chondrites. The variation in the few available near-infrared
reflectance spectra strongly suggests varying compositions among the exogenic
materials. Thus, Bennu might record the remnants of multiple impacts with
different compositions to its parent body, which could have happened in the
very early history of the Solar System. Moreover, at least one of the exogenic
objects is compositionally different from the exogenic materials found on the
similar asteroid (162173) Ryugu, and they suggest different impact tracks.
