Deconvolving Terrestrial Alteration Mineral Signatures from Meteorite Reflectance Measurements …to derive a precise and accurate spectrum of a weathered meteorite to find its true parent body… Sweta Shah Physics Dept. Ithaca College Acknowledgements: Prof: Beth Clark RELAB of Brown University CNS-Physics Department

Earth’s atmosphere chemically alters the original minerals in a meteorite.

Spectroscopy- links a meteorite to its corresponding asteroid in space. Credit: Cornell University and NASA NASA

Goal of the project: Reproduce an uncontaminated spectrum Importance : It will give us a better vision of the source and thus help understand our solar system and its history.

Terrestrial age of a meteorite. Terrestrial age and original chemistry determine the degree to which a meteorite is weathered. A weathered iron meteorite StoneChondrite_Olivine- Hypersthene_L6(weathered crust)

Antarctic meteorite samples – * rusty and evaporitic Hot desert samples- *iron oxides and hydroxides Billygoat Donga meteorite Kind of Weathering

Goethite, Akagenite, Maghemite, Magnetite, Carbonates and/or sulfides of Magnesium Olivine, Pyroxene Troilite olivine goethite akagenite troilite Iddingsite (on rims of olivine)

Spectroscopy –the study of light

Reflectance spectroscopy Study of light as a function of wavelength that has been reflected or scattered from an object. Reflected light is ALBEDO Absorption occurs in many ways.

Absorption processes Electronic absorption

Charge transfer The absorption of a photon causes an electron to move between ions.

Crystal field A crystal field varies with crystal structure from mineral to mineral. Example: ion Fe 2+ Crystal structure of an Olivine

Vibrational processes Exmaples: water and hydroxyl

Approach Spectra Download Minerals (altered and non-altered) Weathered samples Samples’ name: Bishopville-red and META78008,34 Thanks to RELAB of Brown University! – A NASA facility

Enstatite Sodic Plagioclase Diopside Olivine Troilite, and Metal Achondrites – Aubrites BISHOPVILLE Stone. Achondrite aubrite (AUB) Lee County, South Carolina, USA Fell March 25, 1843 Total recovered weight 5.9 kg Specimen weight: 7.8 grams Bishopville-red

Ureilite META78008,34 Like Bishopville Carbonaceous material (graphite and microscopic diamond)

Sample data RELAB Spectral Catalog - TB-RPB-011Brown University Keck/NASA Spectrum TB-RPB-011/LATB11 Wavelength(micron)ReflectanceError … Data for a weathered urelite meteorite

The Mixing Model Program Optimix written in IDL Combines endmembers Simulates a model spectrum

Output data

What we learned Restricted with major minerals Several different models match the spectrum.

Future work Need more minerals Further detailed studies on the alteration of minerals