Variability, absorption features, and parent body searches in “spectrally featureless” meteorite reflectance spectra: Case study – Tagish Lake

M.R.M. Izawa, M.A. Craig, D.M. Applin, J.A. Sanchez, V. Reddy, L. LeCorre, P. Mann, E.A. Cloutis

published online 15 April 2015


Reflectance spectra of many asteroids and other solar system bodies are commonly reported as “featureless”. Here, we show that weak but consistently detectable absorption bands are observable in 200-2500 nm spectra of the Tagish Lake meteorite, a likely compositional and spectral analogue for low-albedo, “spectrally-featureless” asteroids. Tagish Lake presents a rare opportunity to study multiple lithologies within a single meteorite. Reflectance spectra of Tagish Lake display significant variation between different lithologies. The spectral variations are due in part to mineralogical variations between different Tagish Lake lithologies. Ultraviolet reflectance spectra (200-400 nm), few of which have been reported in the literature to date, reveal albedo and spectral ratio variations as a function of mineralogy. Similarly visible-near infrared reflectance spectra reveal variations in albedo, spectral slope, and the presence of weak absorption features that persist across different lithologies and can be attributed to various phases present in Tagish Lake. These observations demonstrate that significant spectral variability may exist between different lithologies of Tagish Lake, which may affect the interpretation of potential source body spectra. It is also important to consider the spectral variability within the meteorite before excluding compositional links between possible parent bodies in the main belt and Tagish Lake. Tagish Lake materials may also be spectral-compositional analogues for materials on the surfaces of other dark asteroids, including some that are targets of upcoming spacecraft missions. Tagish Lake has been proposed as a spectral match for ‘ultra-primitive’ D or P-type asteroids, and the variability reported here may be reflected in spatially or rotationally-resolved spectra of possible Tagish Lake parent bodies and source objects in the near-Earth asteroid population. A search for objects with spectra similar to Tagish Lake has been carried out among the Near-Earth Asteroids. We have identified three possible spectral matches, the best of which are asteroids (326732) 2003 HB6, and (17274) 2000 LC16.