nature.com

A permanent, asymmetric dust cloud around the Moon - Nature

  • ️Sternovsky, Z.
  • ️Wed Jun 17 2015
  • Letter
  • Published: 17 June 2015

Nature volume 522, pages 324–326 (2015)Cite this article

Subjects

Abstract

Interplanetary dust particles hit the surfaces of airless bodies in the Solar System, generating charged1 and neutral2 gas clouds, as well as secondary ejecta dust particles3. Gravitationally bound ejecta clouds that form dust exospheres were recognized by in situ dust instruments around the icy moons of Jupiter4 and Saturn5, but have hitherto not been observed near bodies with refractory regolith surfaces. High-altitude Apollo 15 and 17 observations of a ‘horizon glow’ indicated a putative population of high-density small dust particles near the lunar terminators6,7, although later orbital observations8,9 yielded upper limits on the abundance of such particles that were a factor of about 104 lower than that necessary to produce the Apollo results. Here we report observations of a permanent, asymmetric dust cloud around the Moon, caused by impacts of high-speed cometary dust particles on eccentric orbits, as opposed to particles of asteroidal origin following near-circular paths striking the Moon at lower speeds. The density of the lunar ejecta cloud increases during the annual meteor showers, especially the Geminids, because the lunar surface is exposed to the same stream of interplanetary dust particles. We expect all airless planetary objects to be immersed in similar tenuous clouds of dust.

This is a preview of subscription content, access via your institution

Access options

Subscribe to this journal

Receive 51 print issues and online access

$199.00 per year

only $3.90 per issue

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF

Prices may be subject to local taxes which are calculated during checkout

Additional access options:

Similar content being viewed by others

References

  1. Auer, S. & Sitte, K. Detection technique for micrometeoroids using impact ionization. Earth Planet. Sci. Lett. 4, 178–183 (1968)

    Article  ADS  Google Scholar 

  2. Collette, A., Sternovsky, Z. & Horányi, M. Production of neutral gas by micrometeoroid impacts. Icarus 227, 89–93 (2014)

    Article  ADS  CAS  Google Scholar 

  3. Hartmann, W. K. Impact experiments: 1. Ejecta velocity distributions and related results from regolith targets. Icarus 63, 69–98 (1985)

    Article  ADS  Google Scholar 

  4. Krüger, H., Krivov, A., Hamilton, D. & Grün, E. Detection of an impact-generated dust cloud around ganymede. Nature 399, 558–560 (1999)

    Article  ADS  Google Scholar 

  5. Spahn, F. et al. Cassini dust measurements at Enceladus and implications for the origin of the E ring. Science 311, 1416–1418 (2006)

    Article  ADS  CAS  Google Scholar 

  6. McCoy, J. E. Photometric studies of light scattering above the lunar terminator from Apollo solar corona photography. Proc. Lunar Sci. Conf. 7, 1087–1112 (1976)

    ADS  Google Scholar 

  7. Zook, H. A. & McCoy, J. E. Large scale lunar horizon glow and a high altitude lunar dust exosphere. Geophys. Res. Lett. 18, 2117–2120 (1991)

    Article  ADS  Google Scholar 

  8. Glenar, D. A., Stubbs, T. J., Hahn, J. M. & Wang, Y. Search for a high-altitude lunar dust exosphere using Clementine navigational star tracker measurements. J. Geophys. Res. Planets 119, 2548–2567 (2014)

    Article  ADS  CAS  Google Scholar 

  9. Feldman, P. D. et al. Upper limits for a lunar dust exosphere from far-ultraviolet spectroscopy by LRO/LAMP. Icarus 233, 106–113 (2014)

    Article  ADS  Google Scholar 

  10. Elphic, R. C. et al. The Lunar Atmosphere and Dust Environment Explorer mission. Space Sci. Rev. 185, 3–25 (2014)

    Article  ADS  Google Scholar 

  11. Iglseder, H., Uesugi, K. & Svedhem, H. Cosmic dust measurements in lunar orbit. Adv. Space Res. 17, 177–182 (1996)

    Article  ADS  Google Scholar 

  12. Krivov, A. V., Sremčević, M., Spahn, F., Dikarev, V. V. & Kholshevnikov, K. V. Impact-generated dust clouds around planetary satellites: spherically symmetric case. Planet. Space Sci. 51, 251–269 (2003)

    Article  ADS  Google Scholar 

  13. Buhl, E., Sommer, F., Poelchau, M. H., Dresen, G. & Kenkmann, T. Ejecta from experimental impact craters: particle size distribution and fragmentation energy. Icarus 237, 131–142 (2014)

    Article  ADS  Google Scholar 

  14. Stern, S. A. The lunar atmosphere: history, status, current problems, and context. Rev. Geophys. 37, 453–492 (1999)

    Article  ADS  CAS  Google Scholar 

  15. Sremčević, M., Krivov, A. V., Krüger, H. & Spahn, F. Impact-generated dust clouds around planetary satellites: model versus Galileo data. Planet. Space Sci. 53, 625–641 (2005)

    Article  ADS  Google Scholar 

  16. McNamara, H. et al. Meteoroid Engineering Model (MEM): a meteoroid model for the inner Solar System. Earth Moon Planets 95, 123–139 (2004)

    Article  ADS  Google Scholar 

  17. Dikarev, V. et al. The new ESA meteoroid model. Adv. Space Res. 35, 1282–1289 (2005)

    Article  ADS  Google Scholar 

  18. Nesvorný, D. et al. Dynamical model for the zodiacal cloud and sporadic meteors. Astrophys. J. 743, 129 (2011)

    Article  ADS  Google Scholar 

  19. Rennilson, J. J. & Criswell, D. R. Surveyor observations of lunar horizon-glow. Moon 10, 121–142 (1974)

    Article  ADS  Google Scholar 

  20. Glenar, D. A., Stubbs, T. J., McCoy, J. E. & Vondrak, R. R. A reanalysis of the Apollo light scattering observations, and implications for lunar exospheric dust. Planet. Space Sci. 59, 1695–1707 (2011)

    Article  ADS  Google Scholar 

  21. Markwardt, C. B. in Astronomical Data Analysis Software and Systems XVIII (eds Bohlender, D. A., Durand, D. & Dowler, P.) ASP Conf. Ser. 411, 251 (2009); preprint at http://arxiv.org/abs/0902.2850

    Google Scholar 

  22. Horányi, M. et al. The Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission. Space Sci. Rev. 185, 93–113 (2014)

    Article  ADS  Google Scholar 

  23. Dietzel, H. et al. The HEOS 2 and HELIOS micrometeoroid experiments. J. Phys. E 6, 209–217 (1973)

    Article  ADS  CAS  Google Scholar 

  24. Saito, Y. et al. Solar wind proton reflection at the lunar surface: low energy ion measurement by MAP-PACE onboard SELENE (KAGUYA). Geophys. Res. Lett. 35, L24205 (2008)

    Article  ADS  Google Scholar 

  25. Saul, L. et al. Solar wind reflection from the lunar surface: the view from far and near. Planet. Space Sci. 84, 1–4 (2013)

    Article  ADS  Google Scholar 

  26. Allegrini, F. et al. Lunar energetic neutral atom (ENA) spectra measured by the interstellar boundary explorer (IBEX). Planet. Space Sci. 85, 232–242 (2013)

    Article  ADS  CAS  Google Scholar 

  27. Poppe, A. R., Halekas, J. S., Szalay, J. R., Horányi, M. & Delory, G. T. Model-data comparisons of LADEE/LDEX observations of low-energy lunar dayside ions. Lunar Planet. Sci. Conf. Abstr. 45, 1393 (2014)

    ADS  Google Scholar 

  28. Sremčević, M., Krivov, A. V. & Spahn, F. Impact-generated dust clouds around planetary satellites: asymmetry effects. Planet. Space Sci. 51, 455–471 (2003)

    Article  ADS  Google Scholar 

  29. Auer, S. in Interplanetary Dust (eds Grün, E., Gustafson, B., Dermott, S. & Fechtig., H.) 387–438 (Springer, 2001)

    Google Scholar 

  30. Krüger, H., Krivov, A. V. & Grün, E. A dust cloud of Ganymede maintained by hypervelocity impacts of interplanetary micrometeoroids. Planet. Space Sci. 48, 1457–1471 (2000)

    Article  ADS  Google Scholar 

  31. Koschny, D. & Grün, E. Impacts into ice-silicate mixtures: ejecta mass and size distributions. Icarus 154, 402–411 (2001)

    Article  ADS  CAS  Google Scholar 

  32. Grün, E., Zook, H. A., Fechtig, H. & Giese, R. H. Collisional balance of the meteoritic complex. Icarus 62, 244–272 (1985)

    Article  ADS  Google Scholar 

  33. Drolshagen, G. Comparison of Meteoroid Models. IADC Report No. 24.1 (Inter-Agency Space Debris Coordination Committee, 2009)

    Google Scholar 

Download references

Acknowledgements

The LADEE/LDEX project was supported by NASA. Tests and calibrations were done at the dust accelerator facility of the University of Colorado, supported by NASA’s Solar System Exploration Research Virtual Institute (SSERVI). We are grateful for engineering and technical support from the Laboratory for Atmospheric and Space Physics (LASP), especially from M. Lankton (project manager), S. Gagnard and D. Gathright (mission operations), and D. James (calibration).

Author information

Authors and Affiliations

  1. Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, 80303, Colorado, USA

    M. Horányi, J. R. Szalay, S. Kempf, E. Grün & Z. Sternovsky

  2. Department of Physics, University of Colorado, Boulder, 80309, Colorado, USA

    M. Horányi, J. R. Szalay & S. Kempf

  3. Institute for Modeling Plasma, Atmospheres, and Cosmic Dust (IMPACT), University of Colorado, Boulder, 80303, Colorado, USA

    M. Horányi, J. R. Szalay, S. Kempf, E. Grün & Z. Sternovsky

  4. Astronomy and Space Physics, University of Oulu, Oulu, FI-90014, Finland

    J. Schmidt

  5. Max-Planck-Institut für Kernphysik, Heidelberg, D-69117, Germany

    E. Grün

  6. Institut für Raumfahrtsysteme, Universität Stuttgart, Raumfahrtzentrum Baden Württemberg, Stuttgart, 70569, Germany

    R. Srama

  7. Aerospace Engineering Sciences, University of Colorado, Boulder, 80309, Colorado, USA

    Z. Sternovsky

Authors

  1. M. Horányi

    You can also search for this author in PubMed Google Scholar

  2. J. R. Szalay

    You can also search for this author in PubMed Google Scholar

  3. S. Kempf

    You can also search for this author in PubMed Google Scholar

  4. J. Schmidt

    You can also search for this author in PubMed Google Scholar

  5. E. Grün

    You can also search for this author in PubMed Google Scholar

  6. R. Srama

    You can also search for this author in PubMed Google Scholar

  7. Z. Sternovsky

    You can also search for this author in PubMed Google Scholar

Contributions

M.H. was the instrument principal investigator, directed the data analysis, and was primarily responsible for writing this paper. J.R.S. developed the data analysis software. S.K. was responsible for the calibration of the instrument and contributed to the data analysis. J.S. led the modelling effort. E.G. and R.S. contributed to the analysis and interpretation of the data. Z.S. designed the instrument and contributed to the data analysis.

Corresponding author

Correspondence to M. Horányi.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Detection geometry.

A particle of velocity v is recorded by a detector of sensitive area A. The surface normal of the detector area points along the velocity vector of the spacecraft vsc. The particle enters the instrument with an angle ω measured between the instrument boresight and the relative velocity vector of the particle vsc − v .

Extended Data Figure 2 Systematic approximation error and its dependence on ejection parameters.

a, The calculated density for a standard set of parameters listed in Extended Data Table 1 for the model ejecta cloud12 as function of altitude (black line) normalized to the production rate N+. The density is recalculated using n = γ/(Avsc) (red line), the approach taken in this paper to infer the dust density from the measured impact rates γ, indicating an underestimate of <20% for altitudes below 100 km. b, Contour plot of the ratio of the ‘true’ model density over the recalculated density at the altitude h = 50 km, as a function of the opening cone angle of the ejecta plume ψ0 and the exponent of the power-law initial-speed distribution µ, appropriately setting the minimum speed u0, while keeping the maximum speed constant at 2vescape, maintaining a constant total kinetic energy of the ejecta particles.

Extended Data Figure 3 Comparison of observed and modelled cloud properties.

a, The dust density n(h) of the lunar ejecta cloud as function of altitude and size (colour scale). The continuous black line shows the model prediction12 using the best-fit parameters listed in Extended Data Table 1. b, The cumulative dust mass in the lunar exosphere. The continuous blue line shows the ejecta model prediction (Extended Data Table 1). c, The initial normalized vertical velocity distribution f(u) calculated from n(h) using energy conservation. The continuous line shows f(u) ∝ u−3.4 ± 0.1 matched to the data at u ≥ 400 m s−1 (altitude h ≈ 50 km). Error bars were calculated by propagating the error through the various calculations, where N is the number of detected dust impacts.

Extended Data Figure 4 Modelled flux and mass production in the lunar equatorial plane.

a, The calculated flux of interplanetary dust particles Fimp reaching the lunar equatorial region as a function of lt and t (colour coded for monthly averages). b, The mass production rate, equation (9), calculated using a model for the spatial and velocity distributions of interplanetary dust particles near the Earth16, consistent with the observed asymmetric dust cloud.

Extended Data Table 1 Parameters of the theoretical ejecta cloud model12 for the Moon

Full size table

PowerPoint slides

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Horányi, M., Szalay, J., Kempf, S. et al. A permanent, asymmetric dust cloud around the Moon. Nature 522, 324–326 (2015). https://doi.org/10.1038/nature14479

Download citation

  • Received: 07 October 2014

  • Accepted: 15 April 2015

  • Published: 17 June 2015

  • Issue Date: 18 June 2015

  • DOI: https://doi.org/10.1038/nature14479

This article is cited by

Editorial Summary

A permanent dust ring around the Moon

Before its planned demise on lunar impact in April 2014, NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spent some seven months orbiting the Moon's equator, collecting dust particles for spectroscopic analysis. Sketches made by the Apollo 17 astronauts famously showed a lunar horizon glow, triggering suggestions that electrostatic lofting might be generating dense clouds of small dust particles high above the lunar surface. In this first report on the observations made by the Lunar Dust Experiment (LDEX) onboard LADEE, Mihaly Horànyi et al. find no evidence for such clouds. However, they have detected a permanent asymmetric dust cloud around the Moon, supplied by secondary ejecta dust particles produced by the continual surface impacts of high-speed cometary dust particles in eccentric orbits, as opposed to particles of asteroidal origin following near-circular paths and striking the Moon at lower speeds. The lunar surface is exposed to the same stream of interplanetary dust particles as the Earth, and the LDEX data show that the density of the lunar ejecta cloud increases during meteor showers such as the Geminids.