Space weathering on Eros: Constraints from albedo and spectral measurements of Psyche crater

B. E. Clark, P. Lucey, P. Helfenstein, James Bell, C. Peterson, J. Veverka, T. McConnochie, Mark Robinson, B. Bussey, S. L. Murchie, N. I. Izenberg, C. R. Chapman

Research output: Contribution to journalArticle

80 Citations (Scopus)

Abstract

We present combined multi-spectral imager (MSI) (0.95 μm) and near-infrared spectrometer (NIS) (0.8-2.4 μm) observations of Psyche crater on S-type asteroid 433 Eros obtained by the Near-Earth Asteroid Rendezvous (NEAR)-Shoemaker spacecraft. At 5.3 km in diameter, Psyche is one of the largest craters on Eros which exhibit distinctive brightness patterns consistent with downslope motion of dark regolith material overlying a substrate of brighter material. At spatial scales of 620 m/ spectrum, Psyche crater wall materials exhibit albedo contrasts of 32-40% at 0.946 μm. Associated spectral variations occur at a much lower level of 4-8% (±2-4%). We report results of scattering model and lunar analogy investigations into several possible causes for these albedo and spectral trends: grain size differences, olivine, pyroxene, and troilite variations, and optical surface maturation. We find that the albedo contrasts in Psyche crater are not consistent with a cause due solely to variations in grain size, olivine, pyroxene or lunar-like optical maturation. A grain size change sufficient to explain the observed albedo contrasts would result in strong color variations that are not observed. Olivine and pyroxene variations would produce strong band-correlated variations that are not observed. A simple lunar-like optical maturation effect would produce strong reddening that is not observed. The contrasts and associated spectral variation trends are most consistent with a combination of enhanced troilite (a dark spectrally neutral component simulating optical effects of shock) and lunar-like optical maturation. These results suggest that space weathering processes may affect the spectral properties of Eros materials, causing surface exposures to differ optically from subsurface bedrock. However, there are significant spectral differences between Eros' proposed analog meteorites (ordinary chondrites and/or primitive achondrites), and Eros' freshest exposures of subsurface bright materials. After accounting for all differences in the measurement units of our reflectance comparisons, we have found that the bright materials on Eros have reflectance values at 0.946 μm consistent with meteorites, but spectral continua that are much redder than meteorites from 1.5 to 2.4 μm. Most importantly, we calculate that average Eros surface materials are 30-40% darker than meteorites.

Original languageEnglish (US)
Pages (from-to)1617-1637
Number of pages21
JournalMeteoritics and Planetary Science
Volume36
Issue number12
StatePublished - 2001
Externally publishedYes

Fingerprint

space weathering
albedo
craters
crater
weathering
meteorite
meteorites
maturation
pyroxene
troilite
olivine
grain size
asteroid
asteroids
reflectance
units of measurement
achondrite
achondrites
ordinary chondrite
trends

ASJC Scopus subject areas

  • Geophysics

Cite this

Clark, B. E., Lucey, P., Helfenstein, P., Bell, J., Peterson, C., Veverka, J., ... Chapman, C. R. (2001). Space weathering on Eros: Constraints from albedo and spectral measurements of Psyche crater. Meteoritics and Planetary Science, 36(12), 1617-1637.

Space weathering on Eros : Constraints from albedo and spectral measurements of Psyche crater. / Clark, B. E.; Lucey, P.; Helfenstein, P.; Bell, James; Peterson, C.; Veverka, J.; McConnochie, T.; Robinson, Mark; Bussey, B.; Murchie, S. L.; Izenberg, N. I.; Chapman, C. R.

In: Meteoritics and Planetary Science, Vol. 36, No. 12, 2001, p. 1617-1637.

Research output: Contribution to journalArticle

Clark, BE, Lucey, P, Helfenstein, P, Bell, J, Peterson, C, Veverka, J, McConnochie, T, Robinson, M, Bussey, B, Murchie, SL, Izenberg, NI & Chapman, CR 2001, 'Space weathering on Eros: Constraints from albedo and spectral measurements of Psyche crater', Meteoritics and Planetary Science, vol. 36, no. 12, pp. 1617-1637.
Clark BE, Lucey P, Helfenstein P, Bell J, Peterson C, Veverka J et al. Space weathering on Eros: Constraints from albedo and spectral measurements of Psyche crater. Meteoritics and Planetary Science. 2001;36(12):1617-1637.
Clark, B. E. ; Lucey, P. ; Helfenstein, P. ; Bell, James ; Peterson, C. ; Veverka, J. ; McConnochie, T. ; Robinson, Mark ; Bussey, B. ; Murchie, S. L. ; Izenberg, N. I. ; Chapman, C. R. / Space weathering on Eros : Constraints from albedo and spectral measurements of Psyche crater. In: Meteoritics and Planetary Science. 2001 ; Vol. 36, No. 12. pp. 1617-1637.
@article{747d974f40094b57991992bddedb5674,
title = "Space weathering on Eros: Constraints from albedo and spectral measurements of Psyche crater",
abstract = "We present combined multi-spectral imager (MSI) (0.95 μm) and near-infrared spectrometer (NIS) (0.8-2.4 μm) observations of Psyche crater on S-type asteroid 433 Eros obtained by the Near-Earth Asteroid Rendezvous (NEAR)-Shoemaker spacecraft. At 5.3 km in diameter, Psyche is one of the largest craters on Eros which exhibit distinctive brightness patterns consistent with downslope motion of dark regolith material overlying a substrate of brighter material. At spatial scales of 620 m/ spectrum, Psyche crater wall materials exhibit albedo contrasts of 32-40{\%} at 0.946 μm. Associated spectral variations occur at a much lower level of 4-8{\%} (±2-4{\%}). We report results of scattering model and lunar analogy investigations into several possible causes for these albedo and spectral trends: grain size differences, olivine, pyroxene, and troilite variations, and optical surface maturation. We find that the albedo contrasts in Psyche crater are not consistent with a cause due solely to variations in grain size, olivine, pyroxene or lunar-like optical maturation. A grain size change sufficient to explain the observed albedo contrasts would result in strong color variations that are not observed. Olivine and pyroxene variations would produce strong band-correlated variations that are not observed. A simple lunar-like optical maturation effect would produce strong reddening that is not observed. The contrasts and associated spectral variation trends are most consistent with a combination of enhanced troilite (a dark spectrally neutral component simulating optical effects of shock) and lunar-like optical maturation. These results suggest that space weathering processes may affect the spectral properties of Eros materials, causing surface exposures to differ optically from subsurface bedrock. However, there are significant spectral differences between Eros' proposed analog meteorites (ordinary chondrites and/or primitive achondrites), and Eros' freshest exposures of subsurface bright materials. After accounting for all differences in the measurement units of our reflectance comparisons, we have found that the bright materials on Eros have reflectance values at 0.946 μm consistent with meteorites, but spectral continua that are much redder than meteorites from 1.5 to 2.4 μm. Most importantly, we calculate that average Eros surface materials are 30-40{\%} darker than meteorites.",
author = "Clark, {B. E.} and P. Lucey and P. Helfenstein and James Bell and C. Peterson and J. Veverka and T. McConnochie and Mark Robinson and B. Bussey and Murchie, {S. L.} and Izenberg, {N. I.} and Chapman, {C. R.}",
year = "2001",
language = "English (US)",
volume = "36",
pages = "1617--1637",
journal = "Meteoritics and Planetary Science",
issn = "1086-9379",
publisher = "The University of Arkansas Press",
number = "12",

}

TY - JOUR

T1 - Space weathering on Eros

T2 - Constraints from albedo and spectral measurements of Psyche crater

AU - Clark, B. E.

AU - Lucey, P.

AU - Helfenstein, P.

AU - Bell, James

AU - Peterson, C.

AU - Veverka, J.

AU - McConnochie, T.

AU - Robinson, Mark

AU - Bussey, B.

AU - Murchie, S. L.

AU - Izenberg, N. I.

AU - Chapman, C. R.

PY - 2001

Y1 - 2001

N2 - We present combined multi-spectral imager (MSI) (0.95 μm) and near-infrared spectrometer (NIS) (0.8-2.4 μm) observations of Psyche crater on S-type asteroid 433 Eros obtained by the Near-Earth Asteroid Rendezvous (NEAR)-Shoemaker spacecraft. At 5.3 km in diameter, Psyche is one of the largest craters on Eros which exhibit distinctive brightness patterns consistent with downslope motion of dark regolith material overlying a substrate of brighter material. At spatial scales of 620 m/ spectrum, Psyche crater wall materials exhibit albedo contrasts of 32-40% at 0.946 μm. Associated spectral variations occur at a much lower level of 4-8% (±2-4%). We report results of scattering model and lunar analogy investigations into several possible causes for these albedo and spectral trends: grain size differences, olivine, pyroxene, and troilite variations, and optical surface maturation. We find that the albedo contrasts in Psyche crater are not consistent with a cause due solely to variations in grain size, olivine, pyroxene or lunar-like optical maturation. A grain size change sufficient to explain the observed albedo contrasts would result in strong color variations that are not observed. Olivine and pyroxene variations would produce strong band-correlated variations that are not observed. A simple lunar-like optical maturation effect would produce strong reddening that is not observed. The contrasts and associated spectral variation trends are most consistent with a combination of enhanced troilite (a dark spectrally neutral component simulating optical effects of shock) and lunar-like optical maturation. These results suggest that space weathering processes may affect the spectral properties of Eros materials, causing surface exposures to differ optically from subsurface bedrock. However, there are significant spectral differences between Eros' proposed analog meteorites (ordinary chondrites and/or primitive achondrites), and Eros' freshest exposures of subsurface bright materials. After accounting for all differences in the measurement units of our reflectance comparisons, we have found that the bright materials on Eros have reflectance values at 0.946 μm consistent with meteorites, but spectral continua that are much redder than meteorites from 1.5 to 2.4 μm. Most importantly, we calculate that average Eros surface materials are 30-40% darker than meteorites.

AB - We present combined multi-spectral imager (MSI) (0.95 μm) and near-infrared spectrometer (NIS) (0.8-2.4 μm) observations of Psyche crater on S-type asteroid 433 Eros obtained by the Near-Earth Asteroid Rendezvous (NEAR)-Shoemaker spacecraft. At 5.3 km in diameter, Psyche is one of the largest craters on Eros which exhibit distinctive brightness patterns consistent with downslope motion of dark regolith material overlying a substrate of brighter material. At spatial scales of 620 m/ spectrum, Psyche crater wall materials exhibit albedo contrasts of 32-40% at 0.946 μm. Associated spectral variations occur at a much lower level of 4-8% (±2-4%). We report results of scattering model and lunar analogy investigations into several possible causes for these albedo and spectral trends: grain size differences, olivine, pyroxene, and troilite variations, and optical surface maturation. We find that the albedo contrasts in Psyche crater are not consistent with a cause due solely to variations in grain size, olivine, pyroxene or lunar-like optical maturation. A grain size change sufficient to explain the observed albedo contrasts would result in strong color variations that are not observed. Olivine and pyroxene variations would produce strong band-correlated variations that are not observed. A simple lunar-like optical maturation effect would produce strong reddening that is not observed. The contrasts and associated spectral variation trends are most consistent with a combination of enhanced troilite (a dark spectrally neutral component simulating optical effects of shock) and lunar-like optical maturation. These results suggest that space weathering processes may affect the spectral properties of Eros materials, causing surface exposures to differ optically from subsurface bedrock. However, there are significant spectral differences between Eros' proposed analog meteorites (ordinary chondrites and/or primitive achondrites), and Eros' freshest exposures of subsurface bright materials. After accounting for all differences in the measurement units of our reflectance comparisons, we have found that the bright materials on Eros have reflectance values at 0.946 μm consistent with meteorites, but spectral continua that are much redder than meteorites from 1.5 to 2.4 μm. Most importantly, we calculate that average Eros surface materials are 30-40% darker than meteorites.

UR - http://www.scopus.com/inward/record.url?scp=0035676331&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035676331&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0035676331

VL - 36

SP - 1617

EP - 1637

JO - Meteoritics and Planetary Science

JF - Meteoritics and Planetary Science

SN - 1086-9379

IS - 12

ER -