  Mid-infrared (5 micron to 25 micron) transmission/absorption spectra of
differentiated meteorites (achondrites) were measured to permit comparison with
astronomical observations of dust in different stages of evolution of young
stellar objects. In contrast to primitive chondrites, achondrites underwent
heavy metamorphism and/or extensive melting and represent more advanced stages
of planetesimal evolution. Spectra were obtained from primitive achondrites
(acapulcoite, winonaite, ureilite, and brachinite) and differentiated
achondrites (eucrite, diogenite, aubrite, and mesosiderite silicates). The
ureilite and brachinite show spectra dominated by olivine features, and the
diogenite and aubrite by pyroxene features. The acapulcoite, winonaite,
eucrite, and mesosiderite silicates exhibit more complex spectra, reflecting
their multi-phase bulk mineralogy. Mixtures of spectra of the primitive
achondrites and differentiated achondrites in various proportions show good
similarities to the spectra of the few Myr old protoplanetary disks HD104237A
and V410 Anon 13. A spectrum of the differentiated mesosiderite silicates is
similar to the spectra of the mature debris disks HD172555 and HD165014. A
mixture of spectra of the primitive ureilite and brachinite is similar to the
spectrum of the debris disk HD113766. The results raise the possibility that
materials produced in the early stage of planetesimal differentiation occur in
the protoplanetary and debris disks.
