UV to far-IR reflectance spectra of carbonaceous chondrites – I. Implications for remote characterization of dark primitive asteroids targeted by sample-return missions

We analyse here a wide sample of carbonaceous chondrites from historic falls (e.g. Allende, Cold Bokkeveld, Kainsaz, Leoville, Murchison, Murray, Orgueil and Tagish Lake) and from NASA Antarctic collection. With the analysis of these meteorites we want to get new clues on the role of aqueous alteration in promoting the reflectance spectra diversity evidenced in the most primitive chondrite groups. The selected meteorite specimens are a sample large enough to exemplify how laboratory reflectance spectra of rare groups of carbonaceous chondrites exhibit distinctive features that can be used to remotely characterize the spectra of primitive asteroids. Our spectra cover the full electromagnetic spectrum from 0.2 to 25 μm by using two spectrometers. First one is an ultraviolet (UV)–near-infrared (NIR) spectrometer that covers the 0.2–2 μm window, while the second one is an attenuated total reflectance infrared spectrometer covering the 2–25 μm window. In particular, laboratory analyses in the UV–NIR window allow obtaining absolute reflectance by using standardized measurement procedures. We obtained reflectance spectra of specimens belonging to the CI, CM, CV, CR, CO, CK, CH, R and CB groups of carbonaceous chondrites plus some ungrouped ones, and it allows identifying characteristic features and bands for each class, plus getting clues on the influence of parent body aqueous alteration. These laboratory spectra can be compared with the remote spectra of asteroids, but the effects of terrestrial alteration forming (oxy)hydroxides need to be considered.Current research was supported by the Spanish Ministry of Science and Innovation (project: AYA2011-26522) and CSIC (starting grant #201050I043). JL1 is grateful to ICREA Academia program. ZM acknowledges support from the Royal Society. NASA Meteorite Working Group and Johnson Space Center meteorite curators are acknowledged for providing the Antarctic carbonaceous chondrites. We also want to express our sincere gratitude for the valuable effort made over the years in the recovery of Antartic samples by ANSMET (The Antarctic Search for Meteorites programme). Katsuhito Othsuka and R. H. are also acknowledged for providing some of the carbonaceous chondrites from historic falls