IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2023A027 PROGRAM_TITLE The characterisation of the potentially differentiated Kalliope asteroid family. PROGRAM_INV1 Chrysa Avdellidou PROGRAM_INV2 Marco Delbo PROGRAM_INV3 Kevin Walsh PROGRAM_INV4 Pierre Vernazza PROGRAM_INV5 Michael Marsset PROGRAM_SCICAT main-belt / Trojan asteroids PROGRAM_ABSTRACT_BEG In the classical theory of planetesimal differentiation, a body would form an iron-rich core, an olivine-dominated mantle, and a pyroxene-rich basaltic crust. The detection of differentiated bodies in the current asteroid main belt will allow to get insights and study the very initial phases of planetesimal accretion. So far, the only proof of a differentiated planetesimal is the case of asteroid [4] Vesta and its family, which are linked with the howardite--eucrite--diogenite meteorites that correspond to the crust of a differentiated planetesimal. Spectroscopic searches for other differentiated material have proven successful. However, this material is spread throughout the belt with no connection to each other. The asteroid family of Kalliope belongs to C/X-complex and its members have geometric visible albedos spanning a wide range [0.1-0.35]. Moreover, [22] Kalliope appears to be the densest known solar system small body, supporting the argument for a metallic interior and thus a differentiated body. If the original planetesimal from which Kalliope originates accreted beyond the snow line and contains as much carbon measured in the carbonaceous chondrite meteorites, then the high internal temperatures would lead to the production of materials such as enstatite or other iron-poor pyroxene, metallic iron, and possibly silica. We request IRTF observing time to spectroscopically characterise the largest members of the Kalliope family. In this framework, Kalliope family would be the second discovered differentiated family after Vesta, and the only differentiated family that is potentially linked to carbonaceous-chondrite-related iron meteorites. Near-infrared spectra are required to measure the spectral slope and distinguish the C from the X-complex asteroids and identify [or not] the presence of the 0.9--1 um absorption feature that distinguishes the X-complex classes. The IRTF observations will be combined with the Gaia visible spectra. PROGRAM_ABSTRACT_END