IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2023B033 PROGRAM_TITLE The characterisation of the potentially differentiated Kalliope asteroid family. PROGRAM_INV1 Chrysa Avddellidou 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 to the howardite--eucrite--diogenite meteorites that correspond to the crust of a differentiated planetesimal. The Kalliope asteroid 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 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. From the studies of iron meteorites we now know that also primitive carbonaceous rich planetesimals were differentiated as they achieved high temperatures. We request IRTF observing time, using SpeX and MORIS to spectroscopically characterise the largest members of the Kalliope family. Near-infrared spectra will be combined with the available Gaia DR3 visible spectra and geometric visible albedos from the literature, in order 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. In this framework, Kalliope family would be the second discovered differentiated family after Vesta, and the only differentiated family that originates from a differentiated carbonaceous planetesimal, hence potentially linked to carbonaceous-chondrite-related iron meteorites. PROGRAM_ABSTRACT_END