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Deconvolving Terrestrial
Alteration Mineral Signatures
from Meteorite Reflectance
Measurements
Sweta Shah
Physics Dept.
Ithaca College
…to derive a precise and
accurate spectrum of a
weathered meteorite to find its
true parent body…
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_OlivineHypersthene_L6(weathered crust)
Kind of Weathering
Antarctic meteorite samples –
* rusty and evaporitic
Hot desert samples*iron oxides and hydroxides
Billygoat Donga meteorite
Olivine, Pyroxene
Troilite
Goethite, Akagenite, Maghemite, Magnetite,
Carbonates and/or sulfides of Magnesium
Iddingsite (on rims of olivine)
olivine
troilite
akagenite
goethite
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.
Crystal structure
of an Olivine
Example: ion Fe2+
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
Bishopville-red
Achondrites – Aubrites
•Enstatite
•Sodic Plagioclase
•Diopside
•Olivine
•Troilite, and Metal
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
Ureilite
•Like Bishopville
•Carbonaceous material (graphite
and microscopic diamond)
META78008,34
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