Laboratory mid-IR spectra of equilibrated and igneous meteorites Searching for observables of planetesimal debris

Meteorites contain minerals from Solar System asteroids with differentproperties (like size, presence of water, core formation). We providenew mid-IR transmission spectra of powdered meteorites to obtaintemplates of how mid-IR spectra of asteroidal debris would look like.This is essential for interpreting mid-IR spectra of past and futurespace observatories, like the James Webb Space Telescope. First wepresent new transmission spectra of powdered ordinary chondrite,pallasite and HED meteorites and then we combine them with alreadyavailable transmission spectra of chondrites in the literature, giving atotal set of 64 transmission spectra. In detail we study the spectralfeatures of minerals in these spectra to obtain measurables used tospectroscopically distinguish between meteorite groups. Being able todifferentiate between dust from different meteorite types means we canprobe properties of parent bodies, like their size, if they were wet ordry and if they are differentiated (core formation) or not.We show that the transmission spectra of wet and dry chondrites,carbonaceous and ordinary chondrites and achondrite and chondritemeteorites are distinctly different in a way one can distinguish inastronomical mid-IR spectra. Carbonaceous chondrites type <3(aqueously altered) show distinct features of hydrated silicates(hydrosilicates) compared to the olivine and pyroxene rich ordinarychondrites (dry and equilibrated meteorites). Also the ironconcentration of the olivine in carbonaceous chondrites differs fromordinary chondrites, which can be probed by the wavelength peak positionof the olivine spectral features. The transmission spectra of chondrites(not differentiated) are also strongly different from the achondrite HEDmeteorites (meteorites from differentiated bodies like 4 Vesta), wherethe latter show much stronger pyroxene signatures.The two observables that spectroscopically separate the differentmeteorites groups (and thus the different types of parent bodies) arethe pyroxene-olivine feature strength ratio and the peak shift of theolivine spectral features due to an increase in the iron concentrationof the olivine.