laboratory simulations of planetary surfaces: understanding … · 2020. 1. 3. · coherent...
TRANSCRIPT
-
Robert M. Nelson, Bruce W. Hapke, Mark D. Boryta,
Ken S. Manatt, William D. Smythe, Desiree Kroner,
Adaeze Nebedum
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and Planetary I
Laboratory Simulations of Planetary Surfaces:
Understanding Regolith Physical Properties
from Astronomical Photometric Observations
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Galileo, 1636 Dialogues, p92
Salviati: “You must know then that
a given surface receives more or less
illumination from the same light
according as the rays of light fall
upon it less or more obliquely; the
greatest illumination occurs where the
rays are perpendicular”.
Simplicius: “Please explain further
for me, since I am not that quick
witted.”
The First Bi-directional Reflectance Measurements
-
Reflectance Phase Curve The Reflectance Opposition Effect
Δm
Phase Angle (deg)
-
Reflectance Phase Curve The Reflectance Opposition Effect
Δm
Phase Angle (deg)
-
Reflectance Phase Curve The Reflectance Opposition Effect
Δm
Phase Angle (deg)
-
Polarization Phase Curve The Polarization Opposition Effect
Umov, N (1905). "Chromatische depolarisation durch Lichtzerstreuung". Physik. Z. 6: 674–676 Lyot, B. (1929). Studies of the Polarization of Planets, NASA TT F-187. Lyot, B. 1929. Recherches sur la polarisation de la lumiere des planetes et de queldues substances terrestres. Ann. Obs. Meudon. 8, 1–161. Dollfus, A. (1975) Optical polarimetry of the Galilean satellites of Jupiter. Icarus, 25, pp. 416–435.
-
Polarization Phase Curve The Polarization Opposition Effect
Min
Crossover Point, a.k.a. Inversion Angle
-
Polarization Phase Curve The Polarization Opposition Effect
Min
Crossover Point, a.k.a. Inversion Angle
Slope
-
The Problem for Asteroids α≤30 deg
-
The Problem for Saturnian Satellites α≤7 deg
-
Schematic Representation of Shadow Hiding Opposition Effect (SHOE)
Hapke, B. W. 1963. A Theoretical photometric function for the lunar surface. J. Geophys. Res., 68, 4571-86.
Irvine, W. (1965). Multiple Scattering by Large Particles. Astrophys. J. 142, 1563-1575. Irvine, W. (1966). The Shadowing Effect in Diffuse Reflectance. G. Geophys. Res. 71, 2931-2937.
-
Schematic Representation of Coherent Backscattering Opposition Effect
Shkuratov, Yu. G. 1985. On the origin of the opposition effect and negative polarization for cosmic bodies with solid surface. In Astronomicheskii Circular 1400, pp. 3–6. Sternberg State Astron.
Inst., Moscow. [In Russian] Muinonen, K. 1990. Light Scattering by Inhomogeneous Media: Backward Enhancement and Reversal of Polarization. Ph.D. thesis, University of Helsinki. Hapke, B. 1990. Coherent backscatter and the radar characteristics of outer planet satellites. Icarus 88, 407–417. Mishchenko, M. I. 1992. The angular width of the coherent backscatter opposition effect: An application to icy outer planet satellites. Astrophys. Space Sci. 194, 327–333.
-
Coherent Backscattering vs. Shadow Hiding
If SHOE then most of the returned signal is singly scattered
If CBOE then most of the returned signal is multiply scattered
-
Sketch of optical path
Nelson et al, 1998, 2000,2002
Laboratory Approach: The Goniometric Photopolarimeter (GPP)
-
Nelson et al., 1998, 2000, 2002
0.056 < α < 5 deg
P.M.T.
Distinguishing CBOE from SHOE
-
GPP, 1998,2000,2002
-
Polarization Ratios
-
Expected behavior in LPR and CPR in returned signal
-
CPRLPR, AL203, 1.5 Microns (Nelson et al., 2000)
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Circular polarization ratio increases with
decreasing phase angle in high albedo
particulate materials
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
… consistent with Coherent Backscattering hypothesis
Nelson, R.M., et al., (2000).The Opposition Effect in Simulated Planetary Regoliths. Reflectance and Circular Polarization Ratio Change at Small Phase Angle. Icarus, 147, 545-558. Nelson, R. M. et al. (2002). Low phase angle laboratory studies of the opposition e%ect: search for Wavelengthdependence. Planetary and Space Science 50 (2002) 849 – 856
Circular polarization ratio increases with
decreasing phase angle in high albedo
particulate materials
-
Half Width Half Max vs. Particle Size
It is known theoretically (Stephen and Cwilich, 1986), and demonstrated experimentally in investigations of polystyrene spheres in liquid suspension (Van Abada et al., 1987) that : HWHM ~/2D
Where D is the diffusion length in the medium
D=~ (LsLa/3) 1/2
Ls is mean distance traveled between scatterings La is the mean distance traveled before absorption
However…
-
Mishchenko Predictions
-
Reflectance of 13 Al2O3 powders at 0.633 microns
-
Mischenko Model Compared to Al2O3 powders
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Most probable explanation:
Aluminum Oxide particles are not spherical
-
Rosenbush et al, 2014
The Challenge for Laboratory Investigators
-
0.056 < α < 5 deg Nelson et al., 1998,2000,2002
(P.M.T.)
The Old Configuration
-
Helmholtz Reciprocity Principle
Interchanging the light source and the detector in a bidirectional reflectance
measurement produces the physically identical configuration.
BDRF( i, e, θ)=BDRF(e, i, θ)
Helmholtz, 1859; Stokes, 1849, See Minnaert, 1941; Hapke, 2012, p 264-265
-
Helmholtz Reciprocity Principle
Interchanging the light source and the detector in a bidirectional reflectance
measurement produces the physically identical configuration.
BDRF( i, e, θ)=BDRF(e, i, θ)
Helmholtz, 1859; Stokes, 1849, See Minnaert, 1941; Hapke, 2012, p 264-265
“If I can see you, then you can see me” John W. Strutt, 1873
-
Helmholtz Reciprocity Principle
“If I can see you, then you can see me” John W. Strutt, 1873, (a.k.a. Lord Rayleigh!)
Interchanging the light source and the detector in a bidirectional reflectance
measurement produces the physically identical configuration.
BDRF( i, e, θ)=BDRF(e, i, θ)
Helmholtz, 1859; Stokes, 1849, See Minnaert, 1941; Hapke, 2012, p 264-265
-
Helmholtz configuration of goniometric photopolarimeter is an exact duplication of astronomical measurements.
The New Configuration
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Phase Curve Al2O3, 1.5 and 22.5 microns
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Phase Curve Al2O3, 1.5 and 22.5 microns
Data from 0.1 to 5 degrees are extrapolated to zero to determine peak
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Extrapolation done by two methods
1. Modified Surkatov-Akimov (y=a+b*x+c*exp(-d*x)) 2. New Mount San Antonio College Function (y=a*exp(b*x)+c*exp(d*x))
Akimov, L. A. 1980. Nature of the opposition effect. Vestn. Kharkov State University 204, 3–12.
Shkuratov, Yu. G. 1988. A diffraction mechanism for the formation of the opposition effect of the brightness of surfaces having a complex structure. Kinem.Fiz. Nebes. Tel. 4, 33–39.
Fit to lab data from 0.1 to 5 degrees
Phase Curve Maxima for 13 particle sizes, Al2O3
Particle Size (microns)
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
-
Half Width Half Max vs. Particle Size It is known theoretically (Stephen and Cwilich, 1986), and
demonstrated experimentally in investigations of polystyrene spheres in liquid suspension (Van Abada et al., 1987) that :
HWHM ~/2D Where D is the diffusion length in the medium
D=~ (LsLa/3) 1/2
Ls is mean distance traveled between scatterings La is the mean distance traveled before absorption
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Not consistent with models (Mishchenko (1992) or Hapke (2013))
Mishchenko, M. I. 1992. The angular width of the coherent backscatter opposition effect: An application to icy outer Solar System satellites. Astrophys. Space Sci. 194, 327–333. Hapke, B.W. chapter 9, eq 9.24
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Models are premised on spherical particles.
Aluminum Oxide particles are not spherical.
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Models are premised on spherical particles.
Aluminum Oxide particles are not spherical.
Planetary Regolith Particles are also
not spherical.
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
What about Polarization Phase Curve?
Similar effects reported by Shkuratov et al., 2002, Fig14
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Preliminary Conclusions 1) Reflectance and Polarization Phase Curves depend on particle size
2) In highly reflective, highly porous media, the following also depend on particle size:
a) The location of the polarization minimum, b) The depth of the polarization minimum, c) The slope of the negative branch at the crossover point
3) When particle size is > ~ 2λ, the polarization phase curve is flat
4) It remains to be determined if these effects (2 and 3 above) apply to low albedo materials.
5) Both SHOE and CBOE reflectance mechanisms may have associated polarization phase curves.
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
1. If a reflectance phase curve and a polarization phase curve of solar system object can be obtained (even at a very small range of phase angles), it will soon be possible to determine (or at least constrain) important regolith properties.
2. Future missions to the Jovian system (particularly Europa) would derive great benefit from including polarization measurement capability.
Looking Ahead…
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Acknowledgements Dale P. Cruikshank Jay Gogeun Ludmilla Kolokolova Karri Muinonen Yuriy Shkuratov Ted Roush Nichoas Thomas Gorden Videen Robert A. West Yunzhao Wu
-
August 4, 2015 IAU 2015, FM 12: Dust and Ices II and
Planetary I
Al2O3, Ref@5 deg = 94.6 % SiC, Ref@5deg =22%
The Problem
Little shadow hiding expected in high albedo materials, but…