Transcript Shah-2005 - Ithaca College

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, Nate
RELAB of Brown University
CNS-Physics Department
Earth’s atmosphere
chemically alters the
original minerals
in a meteorite.
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
akagenite
troilite
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.
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+
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
Meteorite measurement samples
The Mixing Model Program
Optimix
• written in IDL
•Combines endmembers
•Simulates a model spectrum
Output data
Our Model Results
Conclusion
•A close match for Bishopville red wheras not for Ureilite
•Several different models match the spectrum.
•Restricted with major minerals
•Include minor minerals
• Further detailed studies on the alteration of minerals