We have initial data from the Lucy mission, and its Sunday flyby of asteroid (52246) Donaldjohanson. We knew it was an elongated asteroid beforehand, and it turns out imagery confirms this (rather than, say, a close binary system, or something else completely).
Ground telescopes could tell something was unusual; the lightcurve of Donaldjohanson has strong peaks and valleys. Traditionally, this means the body appears to brighten and dim, as it turns from side-on to the Sun, to end-on, and back. (We’re guessing it’s not because bodies have brighter and darker faces, like Saturn’s satellite Iapetus.) We can now see from Lucy images that Donaldjohanson has two lobes, joined together. Previous bilobate objects include numerous comets, and the Kuiper-Belt Object (486958) Arrokoth. The ‘neck’ of Donaldjohanson appears filled in with regolith, like 67P/Churyumov-Gerasimenko, or possibly (25143) Itokawa. All in all, Donaldjohanson most resembles the ‘bowling pin’ comet 19P/Borrelly.
Asteroid Donaldjohanson is in the C-complex of asteroid classifications. Given that C-asteroids are organic-rich, water-rich, and likely related to comets, every single one we visit fills us in on the origins of water and life. Lucy’s future targets- the Trojan asteroids near Jupiter- orbit in a cooler region of the Solar System, and beyond the ‘snow line.’ This is the distance from the Sun at which water ice will be stable, instead of sublimating. If the trojans are truly primordial (as old as the Solar System itself, and not captured from elsewhere), they, too, will be puzzle pieces to the history of the Solar System and life itself.