Modeling of the Light Scattering by Dust Particle Plasma near the Moon Surface

1. Modeling of the Light Scattering by Dust Particle Plasma near the Moon Surface G.V.Belokopytov, A.V.Zhuravlev M.V.Lomonosov Moscow State University, Dept. of Physics

2. Outline • Introduction. Lunar dust levitation. • Methods, have been used in lunar dust research • Concentration of chemical elements and their optical properties • Thin layer of non oxidizing iron on dust particles • Size distribution of dust on the ground and above It • Scattering type of lunar dust plasma in visible optical region and near IR.

3. Introduction. Lunar dust levitation. http://lunarscience.nasa.gov

4. Methods, have been used in lunar dust research Electronic microscopy Impact measurement • Sedimentation Electrical charge measurement ? LIDAR measurements Single particle optical levitation

5. Concentration of chemical elements on the Moon • Lunar dust consists not only from pure chemical elements but also from their compounds. • Optical constants of elements and compounds may strongly differ. • http://www.permanent.com/l-apollo.htm

6. Optical properties of main elements and their compounds • Optical constants of elements and compounds comprising lunar dust strongly differ. • [1] Johnson, Christy // Phys. Rev. B 1974, V.9, N.12 • [2] Virgin semiconductors technical report // http://www.virginiasemi.com/pdf/OpticalPropertiesofSilicon71502.doc • [3] Hagemann, Gudat, Kunz // DESY SR-74/7, 1974 • [4] Malitson // J. Opt. Soc. Am., 1965, 55, 1205-1209

7. Scattering efficiencies of nanoparticles with different diameters example for l =400 nm - scattering crossection Scattering efficiency Qsca - radius of the particle Particle diameter D, nm • Difference in optical constants leads to strongly different scattering efficiencies • This in turn complicates optical measurement of nanoparticles concentrations • and size distribution in dusty plasma

8. Thin layer of non oxidizing iron • Lunar dust have thin (approx. 100 nm) layer of non oxidizing iron • Does they all have? Bibring, Durand, // Science V. 175, 1971, P. 753

9. Two scattering types • Multipolar • Dipolar • Dl • Difficult to handle • The scattering diagram depends on particle shape strongly • Nonuniform scattering diagram • D << l • Easy to handle • Uniform scattering in plane, perpendicular to E • Almost independent scattering diagram on particle shape

10. Size distribution of lunar dust particles Apollo 11 Apollo 17 Diameter (mm) Diameter (mm) Apollo 16 Diameter (mm) Liu,Taylor// NLSI Lunar Science Conference (2008)

11. There is estimation of particle distribution in levitating dust Size distribution f(D) Golub’, Dol’nikov, Zakharov, et al. // JETP Lett., 2012, V. 95, N. 4, P. 182

12. Numerical Results. Determination of the scattering type Averaged over size distribution scattering diameter <Dsca> Size distribution f(D) all modes on ground dipole modes above ground

13. Conclusions • There is background to suppose that the size distribution of levitating particles differs from one on the ground in the direction of decreasing diameters up to one order of magnitude. • The scattering type of dusty plasma particles in visible and IR range is dipolar in case that mean diameter is about 10 nm, and multipolar when mean diameter is about 100 nm.

14. Conclusions • The frequency and angular spectrum of scattered radiation is strongly dependent on the chemical composition of the lunar dust particles. • Thin non oxidizing iron layer on certain portion of dust particles helps to decrease influence of variability of chemical composition. The concentration of particles with this layer should be investigated.

15. for your attention