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

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 Fe2+

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, USAFell March 25, 1843Total 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) Reflectance Error

0.32 0.123529 0.0001

0.33 0.121921 0.0001

…

2.59987 0.341959 0.0001

2.60117 0.343273 0.0001

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