scholarly journals Distinguishing between Shock-darkening and Space-weathering Trends in Ordinary Chondrite Reflectance Spectra

2020 ◽  
Vol 1 (2) ◽  
pp. 37
Author(s):  
Tomas Kohout ◽  
Antti Penttilä ◽  
Paul Mann ◽  
Ed Cloutis ◽  
Jan Čuda ◽  
...  
Keyword(s):  
Ordinary Chondrite ◽  
Reflectance Spectra ◽  
Space Weathering

Rigorous light-scattering simulations of space-weathering effects on reflectance spectra

2021 ◽  
Author(s):  
Antti Penttilä ◽  
Timo Väisänen ◽  
Johannes Markkanen ◽  
Julia Martikainen ◽  
Tomas Kohout ◽  
...  
Keyword(s):  
Light Scattering ◽  
Reflectance Spectra ◽  
Space Weathering ◽  
Spectral Slope ◽  
Simulation Tools ◽  
Multi Scale ◽  
Spectral Bands ◽  
Size Scales ◽  
Weathering Effects

<p>We present a multi-scale light-scattering model that is capable of simulating the reflectance spectra of a regolith layer. In particular, the model can be applied to a case where the regolith grains have varying amounts of nanophase inclusions due to space weathering of the material. As different simulation tools are employed for different size scales of the target geometry (roughly, nano-, micro-, and millimeter scales), the particle size effects, the surface reflections, and the volume scattering can all be properly accounted for. Our results with olivine grains and nanophase iron inclusions verify the role of the nanoinclusions in the reflectance spectra of space-weathered materials. Together with the simulation results, we give simplified explanations for the space-weathering effects based on light scattering, namely the decrease of albedo, the general increase of the red spectral slope, and the dampening of the spectral bands. We also consider the so-called ultraviolet bluing effect and show how the change in the spectral slope over the ultraviolet-visual wavelengths is due to the decrease of reflectance in the visual wavelengths rather than the increase of reflectance in the ultraviolet part.</p>

scholarly journals Rigorous light-scattering simulations of nanophase iron space-weathering effects on reflectance spectra of olivine grains

Icarus ◽  
2020 ◽  
Vol 345 ◽  
pp. 113727 ◽  
Author(s):  
Antti Penttilä ◽  
Timo Väisänen ◽  
Johannes Markkanen ◽  
Julia Martikainen ◽  
Tomáš Kohout ◽  
...  
Keyword(s):  
Light Scattering ◽  
Reflectance Spectra ◽  
Space Weathering ◽  
Weathering Effects ◽  
Nanophase Iron

scholarly journals Q-type asteroids: Possibility of non-fresh weathered surfaces

2019 ◽  
Vol 71 (5) ◽  
Author(s):  
Sunao Hasegawa ◽  
Takahiro Hiroi ◽  
Katsuhito Ohtsuka ◽  
Masateru Ishiguro ◽  
Daisuke Kuroda ◽  
...  
Keyword(s):  
Surface State ◽  
Laboratory Experiments ◽  
Fine Particles ◽  
Ordinary Chondrite ◽  
Formation Mechanisms ◽  
Space Weathering ◽  
Ordinary Chondrites ◽  
New Hypothesis

Abstract Itokawa particles, which are samples recovered from the S-complex asteroid 25143 Itokawa by the Hayabusa spacecraft, demonstrate that S-complex asteroids are parent bodies of ordinary chondrite meteorites. Furthermore, they clarify that the space-weathering age of the Itokawa surface is of the order of several thousand years. Traditionally, Q-type asteroids have been considered fresh-surfaced. However, as the space-weathering timescale is approximately three orders of magnitude lesser than the conventionally considered age, the previously proposed formation mechanisms of Q-type asteroids cannot sufficiently explain the surface refreshening. In this study, we propose a new hypothesis on the surface state of Q-type asteroids: Q-type asteroids have a non-fresh weathered surface with a paucity of fine particles. For verifying this hypothesis, laboratory experiments on the space weathering of ordinary chondrites are performed. Based on the results of these experiments, we found that large (more than $100\, \mu \mathrm{m}$) ordinary chondritic particles with space weathering exhibit spectra consistent with Q-type asteroids.

scholarly journals 5. Asteroid Infrared Reflectances and Compositional Implications

1977 ◽  
Vol 39 ◽  
pp. 229-241
Author(s):  
D. L. Matson ◽  
T. V. Johnson ◽  
G. J. Veeder
Keyword(s):  
Optical Properties ◽  
Metallic Phase ◽  
The State ◽  
Reflectance Spectra ◽  
Space Weathering ◽  
Infrared Reflectance ◽  
Reflectance Measurements

This paper assesses the state of asteroid infrared reflectance measurements and discusses what they have contributed to our understanding of asteroidal surfaces. The data suggest that space weathering has not significantly affected the optical properties of the asteroids. Thus comparisons of asteroid reflectance spectra with unweathered meteorite and rock data is a valid procedure. The high 1.6 and 2.2 μm reflectances of a number of asteroids strongly suggest the presence of a metallic phase.

scholarly journals The mystery of 506.5 nm feature of reflectance spectra of Vesta and Vestoids: Evidence for space weathering?

2001 ◽  
Vol 53 (11) ◽  
pp. 1071-1075 ◽  
Author(s):  
Takahiro Hiroi ◽  
Carlé M Pieters ◽  
Faith Vilas ◽  
Sho Sasaki ◽  
Yoshimi Hamabe ◽  
...  
Keyword(s):  
Reflectance Spectra ◽  
Space Weathering

scholarly journals Reflectance spectra of seven lunar swirls examined by statistical methods: A space weathering study

Icarus ◽  
2019 ◽  
Vol 333 ◽  
pp. 516-527 ◽  
Author(s):  
Kateřina Chrbolková ◽  
Tomáš Kohout ◽  
Josef Ďurech
Keyword(s):  
Statistical Methods ◽  
Reflectance Spectra ◽  
Space Weathering

scholarly journals Space Weathering of S-Complex Asteroids Manifested in the UV/Blue: Recent Insights and Future Directions

2015 ◽  
Vol 10 (S318) ◽  
pp. 201-205
Author(s):  
Faith Vilas ◽  
Amanda R. Hendrix
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Uv Absorption ◽  
Reflectance Spectra ◽  
Absorption Feature ◽  
Space Weathering ◽  
The Moon ◽  
Future Directions ◽  
Absorption Features ◽  
Weathering Effects

AbstractSpace weathering affects reflectance spectra of the Moon and S-complex asteroids by spectral bluing (increasing reflectance with decreasing wavelength) of their surface materials at UV/blue (less than 400 nm) wavelengths. This spectral bluing is attributed to a degradation of the UV absorption feature seen in spectral reflectance of olivine as a result of the creation of nanophase (npFe0) iron. We have modeled the effect of the addition of small amounts of npFe0 intimately mixed with particles from a hypothetical material and a terrestrial basalt. The addition of 0.0001% npFe0 affects the reflectance at these UV/blue wavelengths, while the addition of 0.01% is required to see the visible/near infrared reddening and diminution of VNIR absorption features. Thus, the UV/blue spectral reflectance characteristics allow earlier detection of the onset of space weathering effects.

Study of vegetation red edge indices of reflectance spectra for crops of winter wheat cultivated in the steppe zone of Ukraine

2012 ◽  
Vol 18 (4(77)) ◽  
pp. 45-51
Author(s):  
G.M. Zholobak ◽  
◽  
Z.M. Shportiuk ◽  
O.N. Sibirtseva ◽  
S.S. Dugin ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Steppe Zone ◽  
Reflectance Spectra ◽  
Red Edge

Color Space Transformation using Neural Networks

2019 ◽  
Vol 2019 (1) ◽  
pp. 153-158
Author(s):  
Lindsay MacDonald
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Color Space ◽  
Reflectance Spectra ◽  
Network Architectures ◽  
Color Spaces ◽  
Natural Materials ◽  
Space Transformation ◽  
Color Space Transformation

We investigated how well a multilayer neural network could implement the mapping between two trichromatic color spaces, specifically from camera R,G,B to tristimulus X,Y,Z. For training the network, a set of 800,000 synthetic reflectance spectra was generated. For testing the network, a set of 8,714 real reflectance spectra was collated from instrumental measurements on textiles, paints and natural materials. Various network architectures were tested, with both linear and sigmoidal activations. Results show that over 85% of all test samples had color errors of less than 1.0 ΔE2000 units, much more accurate than could be achieved by regression.

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