Spectral calibration for deriving surface mineralogy of Asteroid (25143) Itokawa from Hayabusa Near-Infrared Spectrometer (NIRS) data

Megha Bhatt, Vishnu Reddy, Lucille Le Corre, Juan A. Sanchez, Tasha Dunn, Matthew Richar Izawa, Jian Yang Li, Kris J. Becker, Lynn Weller

Research output: Contribution to journalArticle

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Abstract

We present spectral calibration equations for determining mafic silicate composition of near-Earth asteroid (25143) Itokawa from visible/near-infrared (VNIR) spectra (0.85-2.1. μm) measured using the Near Infrared Spectrometer (NIRS) on board the Japanese Hayabusa spacecraft. Itokawa was the target of the Hayabusa sample return mission and has a surface composition similar to LL chondrites. Existing laboratory spectral calibrations (e.g., Dunn, T.L. et al. [2010]. Icarus 208, 789-797) use a spectral wavelength range that is wider (0.75-2.5. μm) than that of the NIRS instrument (0.85-2.1. μm), making them unfit for interpreting the Hayabusa spectral data currently archived in the Planetary Data System (PDS). We used laboratory near-infrared (NIR) reflectance spectra of ordinary chondrites (H, L and LL) from the study of Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797), which we resampled to the NIRS wavelength range. Using spectral parameters extracted from these resampled spectra we established a relationship between band parameters and mafic silicate compositions (olivine and low-Ca pyroxene). We found a correlation >90% between mafic silicate compositions (fayalite and ferrosilite mol.%) estimated by our spectral method, and electron microprobe measured values from Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797). The standard deviation between the measured and estimated values is 1.5 and 1.1. mol.% for fayalite and ferrosilite, respectively. To test the validity of the new equations we blind tested them using nine laboratory spectra of L and LL chondrites with well-known compositions. We found that the absolute difference between the measured and computed values is in the range 0.1-1.6. mol.%. Our study demonstrates that this new calibration is robust and can be applied to Hayabusa NIRS data despite its limited spectral range (0.85-2.1. μm). We applied the equations to a subset of uncalibrated (no photometric corrections) NIRS spectra and we obtained fayalite and ferrosilite values that are consistent with Itokawa having a LL chondrite surface composition. We intend to develop a photometric model to calibrate the NIRS spectra to standard viewing geometry and apply the new equations to create a global mineralogical map of Itokawa.

Original languageEnglish
Pages (from-to)124-130
Number of pages7
JournalIcarus
Volume262
DOIs
Publication statusPublished - Dec 1 2015
Externally publishedYes

Fingerprint

infrared spectrometers
mineralogy
asteroids
asteroid
near infrared
spectrometer
chondrites
fayalite
calibration
silicates
chondrite
Japanese spacecraft
silicate
sample return missions
data systems
spectral methods
wavelength
olivine
wavelengths
set theory

Keywords

  • Asteroid Itokawa
  • Asteroids, composition
  • Asteroids, surfaces
  • Meteorites
  • Spectroscopy

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Spectral calibration for deriving surface mineralogy of Asteroid (25143) Itokawa from Hayabusa Near-Infrared Spectrometer (NIRS) data. / Bhatt, Megha; Reddy, Vishnu; Le Corre, Lucille; Sanchez, Juan A.; Dunn, Tasha; Richar Izawa, Matthew; Li, Jian Yang; Becker, Kris J.; Weller, Lynn.

In: Icarus, Vol. 262, 01.12.2015, p. 124-130.

Research output: Contribution to journalArticle

Bhatt, Megha ; Reddy, Vishnu ; Le Corre, Lucille ; Sanchez, Juan A. ; Dunn, Tasha ; Richar Izawa, Matthew ; Li, Jian Yang ; Becker, Kris J. ; Weller, Lynn. / Spectral calibration for deriving surface mineralogy of Asteroid (25143) Itokawa from Hayabusa Near-Infrared Spectrometer (NIRS) data. In: Icarus. 2015 ; Vol. 262. pp. 124-130.
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abstract = "We present spectral calibration equations for determining mafic silicate composition of near-Earth asteroid (25143) Itokawa from visible/near-infrared (VNIR) spectra (0.85-2.1. μm) measured using the Near Infrared Spectrometer (NIRS) on board the Japanese Hayabusa spacecraft. Itokawa was the target of the Hayabusa sample return mission and has a surface composition similar to LL chondrites. Existing laboratory spectral calibrations (e.g., Dunn, T.L. et al. [2010]. Icarus 208, 789-797) use a spectral wavelength range that is wider (0.75-2.5. μm) than that of the NIRS instrument (0.85-2.1. μm), making them unfit for interpreting the Hayabusa spectral data currently archived in the Planetary Data System (PDS). We used laboratory near-infrared (NIR) reflectance spectra of ordinary chondrites (H, L and LL) from the study of Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797), which we resampled to the NIRS wavelength range. Using spectral parameters extracted from these resampled spectra we established a relationship between band parameters and mafic silicate compositions (olivine and low-Ca pyroxene). We found a correlation >90{\%} between mafic silicate compositions (fayalite and ferrosilite mol.{\%}) estimated by our spectral method, and electron microprobe measured values from Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797). The standard deviation between the measured and estimated values is 1.5 and 1.1. mol.{\%} for fayalite and ferrosilite, respectively. To test the validity of the new equations we blind tested them using nine laboratory spectra of L and LL chondrites with well-known compositions. We found that the absolute difference between the measured and computed values is in the range 0.1-1.6. mol.{\%}. Our study demonstrates that this new calibration is robust and can be applied to Hayabusa NIRS data despite its limited spectral range (0.85-2.1. μm). We applied the equations to a subset of uncalibrated (no photometric corrections) NIRS spectra and we obtained fayalite and ferrosilite values that are consistent with Itokawa having a LL chondrite surface composition. We intend to develop a photometric model to calibrate the NIRS spectra to standard viewing geometry and apply the new equations to create a global mineralogical map of Itokawa.",
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AU - Bhatt, Megha

AU - Reddy, Vishnu

AU - Le Corre, Lucille

AU - Sanchez, Juan A.

AU - Dunn, Tasha

AU - Richar Izawa, Matthew

AU - Li, Jian Yang

AU - Becker, Kris J.

AU - Weller, Lynn

PY - 2015/12/1

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N2 - We present spectral calibration equations for determining mafic silicate composition of near-Earth asteroid (25143) Itokawa from visible/near-infrared (VNIR) spectra (0.85-2.1. μm) measured using the Near Infrared Spectrometer (NIRS) on board the Japanese Hayabusa spacecraft. Itokawa was the target of the Hayabusa sample return mission and has a surface composition similar to LL chondrites. Existing laboratory spectral calibrations (e.g., Dunn, T.L. et al. [2010]. Icarus 208, 789-797) use a spectral wavelength range that is wider (0.75-2.5. μm) than that of the NIRS instrument (0.85-2.1. μm), making them unfit for interpreting the Hayabusa spectral data currently archived in the Planetary Data System (PDS). We used laboratory near-infrared (NIR) reflectance spectra of ordinary chondrites (H, L and LL) from the study of Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797), which we resampled to the NIRS wavelength range. Using spectral parameters extracted from these resampled spectra we established a relationship between band parameters and mafic silicate compositions (olivine and low-Ca pyroxene). We found a correlation >90% between mafic silicate compositions (fayalite and ferrosilite mol.%) estimated by our spectral method, and electron microprobe measured values from Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797). The standard deviation between the measured and estimated values is 1.5 and 1.1. mol.% for fayalite and ferrosilite, respectively. To test the validity of the new equations we blind tested them using nine laboratory spectra of L and LL chondrites with well-known compositions. We found that the absolute difference between the measured and computed values is in the range 0.1-1.6. mol.%. Our study demonstrates that this new calibration is robust and can be applied to Hayabusa NIRS data despite its limited spectral range (0.85-2.1. μm). We applied the equations to a subset of uncalibrated (no photometric corrections) NIRS spectra and we obtained fayalite and ferrosilite values that are consistent with Itokawa having a LL chondrite surface composition. We intend to develop a photometric model to calibrate the NIRS spectra to standard viewing geometry and apply the new equations to create a global mineralogical map of Itokawa.

AB - We present spectral calibration equations for determining mafic silicate composition of near-Earth asteroid (25143) Itokawa from visible/near-infrared (VNIR) spectra (0.85-2.1. μm) measured using the Near Infrared Spectrometer (NIRS) on board the Japanese Hayabusa spacecraft. Itokawa was the target of the Hayabusa sample return mission and has a surface composition similar to LL chondrites. Existing laboratory spectral calibrations (e.g., Dunn, T.L. et al. [2010]. Icarus 208, 789-797) use a spectral wavelength range that is wider (0.75-2.5. μm) than that of the NIRS instrument (0.85-2.1. μm), making them unfit for interpreting the Hayabusa spectral data currently archived in the Planetary Data System (PDS). We used laboratory near-infrared (NIR) reflectance spectra of ordinary chondrites (H, L and LL) from the study of Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797), which we resampled to the NIRS wavelength range. Using spectral parameters extracted from these resampled spectra we established a relationship between band parameters and mafic silicate compositions (olivine and low-Ca pyroxene). We found a correlation >90% between mafic silicate compositions (fayalite and ferrosilite mol.%) estimated by our spectral method, and electron microprobe measured values from Dunn et al. (Dunn, T.L. et al. [2010]. Icarus 208, 789-797). The standard deviation between the measured and estimated values is 1.5 and 1.1. mol.% for fayalite and ferrosilite, respectively. To test the validity of the new equations we blind tested them using nine laboratory spectra of L and LL chondrites with well-known compositions. We found that the absolute difference between the measured and computed values is in the range 0.1-1.6. mol.%. Our study demonstrates that this new calibration is robust and can be applied to Hayabusa NIRS data despite its limited spectral range (0.85-2.1. μm). We applied the equations to a subset of uncalibrated (no photometric corrections) NIRS spectra and we obtained fayalite and ferrosilite values that are consistent with Itokawa having a LL chondrite surface composition. We intend to develop a photometric model to calibrate the NIRS spectra to standard viewing geometry and apply the new equations to create a global mineralogical map of Itokawa.

KW - Asteroid Itokawa

KW - Asteroids, composition

KW - Asteroids, surfaces

KW - Meteorites

KW - Spectroscopy

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