# A Large Basin on the Near Side of the Moon

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## Abstract

The differences between the surface structure of the near side and the far side of the Moon have been topics of interest ever since photographs of the far side have been available. One recurrent hypothesis is that a large impact on the near side has deposited ejecta on the far side, resulting in thicker crust there. Specific proposals were made by P.H. Cadogan for the Gargantuan Basin and by E.A. Whitaker for the Procellarum Basin. Despite considerable effort, no consensus has been reached on the existence of these basins. The problem of searching for such a basin is one of finding its signature in a somewhat chaotic field of basin and crater impacts. The search requires a model of the topographic shape of an impact basin and its ejecta field. Such a model is described, based on elevation data of lunar basins collected by the Lidar instrument of the Clementine mission and crustal thickness data derived from tracking Clementine and other spacecraft. The parameters of the model are scaled according to the principles of dimensional analysis and isostatic compensation in the early Moon. The orbital dynamics of the ejecta and the curvature of the Moon are also taken into account. Using such a scaled model, a search for the best fit for a large basin led to identification of a basin whose cavity covers more than half the Moon, including the area of all of the impact basins visible on the near side. The center of this basin is at 22 degrees east longitude and 8.5 degrees north latitude and its average radius is approximately 3,160 km. It is a megabasin, a basin that contains other basins (the far side South Pole-Aitken Basin also qualifies for that designation). It has been called the Near Side Megabasin. Much of the material ejected from the basin escaped the Moon, but the remainder formed an ejecta blanket that covered all of the far side beyond the basin rim to a depth of from 6 to 30 km. Isostatic compensation reduced the depth relative to the mean surface to a range of 1–5 km, but the crustal thickness data reveals the full extent of the original ejecta. The elevation profile of the ejecta deposited on the far side, together with modification for subsequent impacts by known basins (especially the far side South Pole-Aitken Basin) matches the available topographic data to a high degree. The standard deviation of the residual elevations (after subtracting the model from the measured elevations) is about one-half of the standard deviation of the measured elevations. A section on implications discusses the relations of this giant basin to known variations in the composition, mineralogy, and elevations of different lunar terranes.

## Keywords

Moon Lunar basins Multi-ringed basins Multi-ring basins Impact basins Basin ejecta Clementine Near Side Megabasin South Pole-Aitken Basin## Notes

### Acknowledgements

The author has had the benefit of conversations with the authors of many of the referenced publications. Particular gratitude is due to Hajime Hikida and Mark Wieczorek for sharing their crustal thickness data. The reviewers of this paper made many constructive suggestions that have been incorporated. Greg Neumann has been very helpful with suggestions for additional figures and analysis.

## References

- B.A. Archinal, Final completion of the Unified Lunar Control Network 2005 and the lunar topographic model, LPSC XXXVIII, Abstract 1904 (2007)Google Scholar
- A.B. Binder, Lunar Prospector: overview. Science
**281**, 1475–1476 (1998)Google Scholar - B. Bussey, P.D. Spudis,
*The Clementine Atlas of the Moon*. Cambridge University Press (2004)Google Scholar - C.J. Byrne, Automated cosmetic improvement of mosaics from the Lunar Orbiter Atlas, LPSC XXXIII, Abstract 1260 (2002)Google Scholar
- C.J. Byrne, Evidence for three basins beneath Oceanus Procellarum, LPSC XXXV, Abstract 1103 (2004)Google Scholar
- C.J. Byrne,
*Lunar Orbiter Photographic Atlas of the Near Side of the Moon*. Springer-Verlag, London (2005)Google Scholar - C.J. Byrne, Radial profiles of lunar basins, LPSC XXXVII, Abstract 1900 (2006a)Google Scholar
- C.J. Byrne, The Near Side Megabasin of the Moon, LPSC XXXVII, Abstract 1930 (2006b)Google Scholar
- C.J. Byrne,
*The Far Side of the Moon: A Photographic Guide*. Springer-Verlag, New York (2008)Google Scholar - P.H. Cadogan, Oldest and largest lunar basin? Nature
**250**(5464), 315–316 (1974)CrossRefADSGoogle Scholar - G. Chin, A. Bartels, S. Brylow, M. Foote, J. Garvin, J. Kaspar, J. Keller, I. Mitrofanov, K. Raney, M. Robinson, D. Smith, H. Spence, P. Spudis, S.A. Stern, M. Zuber, Lunar reconnaissance Orbiter overview: the instrument suite and mission, LPSC XXVII, Abstract 1949 (2006)Google Scholar
- R.C. Elphic, D.J. Lawrence, W.C. Feldman, B.L. Burraclough, O.M. Gasnault, S. Maurice, P.G. Lucey, D.T. Blewett, Lunar Prospector neutron spectrometer constraints on TiO
_{2}. JGR**107**(E4), 5024 (2002), doi: 10.1029/2000JE001460 Google Scholar - W.C. Feldman, O. Gasnault, S. Maurice, D.J. Lawrence, R.C. Elphic, P.G. Lucey, A.B. Binder, Global distribution of lunar composition: new results from Lunar Prospector. JGR
**107**(E3), 5016 (2002), doi: 10.1029/2001JE001506 Google Scholar - I. Garrick-Bethell, Ellipses of the South Pole-Aitken Basin: implications for basin formation, LPSC XXXV, Abstract 1515 (2004)Google Scholar
- I. Garrick-Bethell, I.J. Wisdom, M.T. Zuber, Evidence for a past high-eccentricity lunar orbit. Science
**313**, 652–655 (2006)Google Scholar - O. Gasnault, W.C. Feldman, C. d’Uston, D.J. Lawrence, S. Maurice, S.D. Chevrel, P.C. Pinet, R.C. Elphic, I. Genetay, K.R. Moore, Statistical analysis of thorium and fast neutron data at the lunar surface. JGR
**107**(E10), 5072 (2002), doi: 10.1029/2000JE001461 Google Scholar - S.H. Hikida, H. Mizutani, Earth, planets, and space
**57**, 1121–1126 (2005)Google Scholar - S.H. Hikida, M.A. Wieczorek, Crustal thickness of the Moon: new constraints from gravity inversion using polyhedral shape models, LPSC 2007, Abstract #1547 (2007)Google Scholar
- K.R. Housen, R.M. Schmidt, K.A. Holsapple, Crater ejecta scaling laws: fundamental forms based on dimensional analysis. JGR
**88**(B3), 2485–2499 (1983)Google Scholar - B.A. Ivanov, The effect of gravity on crater formation: thickness of ejecta and concentric basins. in
*Proceeding of the Lunar Science Conference, 7th*(1976)Google Scholar - B.A. Ivanov, Lunar impact basins—numerical modeling, LPSC XXXVII, Abstract 2003 (2007)Google Scholar
- B.L. Jolliff, J.J. Gillis, L.A. Haskin, R.L. Korotev, M.A. Wieczorek, Major lunar crustal terranes: surface expressions and crust-mantle origins. JGR
**105**(E2), 4197–4216 (2000)Google Scholar - D.J. Lawrence, W.C. Feldman, B.L. Barraclough, A.B. Binder, R.C. Elphic, S. Maurice, M.C. Miller, T.H. Prettyman, Thorium abundances on the lunar surface. JGR
**195**(E8), 20,307–20,331 (2000)Google Scholar - D.J. Lawrence, W.C. Feldman, R.C. Wlphic, R.C. Little, T.H. Prettyman, S. Maurice, P.G. Lucey, Iron abundances on the lunar surface as measured by the Lunar Prospector gamma-ray and neutron spectrometers. JGR
**107**(E12), 5130 (2002), doi: 10.1029/2001JE001530 Google Scholar - P.G. Lucey, P.D. Spudis, M. Zuber, D. Smith, E. Malaret, Topographic-compositional units on the Moon and the early evolution of the lunar crust. Science
**266**, 1855–1858 (1994)Google Scholar - P. Lucey, R.L. Korotev, J.J. Gillis, L.A. Taylor, D. Lawrence, B.A. Campbell, R. Elphic, B. Feldman, L.L. Hood, D. Hunten, M. Mendillo, S. Noble, J.J. Papike, R.C. Reedy, S. Lawson, T. Prettyman, O. Gasnault, S. Maurice, Understanding the lunar surface and space–Moon interactions in the book
*New Views of the Moon*, reviews in mineralogy and geochemistry. Mineralogical Society of America**60**, 83–220 (2006)Google Scholar - H.J. Melosh,
*Impact Cratering. A Geologic Process*. Oxford University Press (1989)Google Scholar - G.A. Neumann, M.T. Zuber, D.E. Smith, F.G. Lemoine, The lunar crust: global structure and signature of major basins. JGR
**101**(E7), 16,841–16,843 (1996)Google Scholar - S. Nozette et al., The Clementine mission to the moon. Science
**266**, 1835–1839 (1994)Google Scholar - N.E. Petro, C.M. Pieters, Surviving the heavy bombardment: ancient material at the surface of South Pole-Aitken basin. JGR
**109**(E06004) (2004), doi: 1029/2003JE002182 - N.E. Petro, C.M. Pieters, The lunar-wide effects of the formation of basins on the megaregolith, LPSC XXXVI, Abstract 1209 (2005)Google Scholar
- J.E. Richardson, Improving the modeling of impact ejecta behavior: the effects of gravity and strength near the crater rim, LPSC XXXVIII, Abstract 1345 (2007)Google Scholar
- P.H. Schultz, A possible link between Procellarum and the South Pole-Aitken Basin, LPSC XXXVIII, Abstract 1839 (2007)Google Scholar
- P.D. Spudis,
*The Geology of Multi-ring Impact Basins*. Cambridge University Press (1993)Google Scholar - W.T. Thomson,
*Introduction to Space Dynamics*. Dover (1986)Google Scholar - E.P. Turtle, E. Pierazzo, G.S. Collins, G.R. Osinski, H.J. Melosh, J.V. Morgan, W.U. Reimold, Impact structures: what does crater diameter mean? Geological Society of America, Special Paper
**384**, 1–24 (2005)Google Scholar - E.A. Whitaker, The lunar procellarum basin, in multi-ring basins, LPSCP 12, Part A (1981)Google Scholar
- M.A. Wieczorek, R.J. Phillips, The structure of lunar basins: implications for basin forming processes, LPSC XXIX, Abstract 1299 (1998)Google Scholar
- M.A. Wieczorek, R.J. Phillips, The Porcellarum KREEP terrane. Implications for mare volcanism and lunar evolution. JGR
**105**(E8), 20,417–20,430 (2000)Google Scholar - M.A. Wieczorek, R.J. Phillips, R.L. Korotev, B.L. Jolliff, L.A. Haskin, Geophysical evidence for the existence of the lunar Procellarum KREEP terrane, LPSC XXX, Abstract 1548 (1999)Google Scholar
- D.E. Wilhelms,
*The Geologic History of the Moon*. USGS Professional Paper 1384, US Government Printing Office, Washington, DC (1987)Google Scholar - K.K. Williams, M.T. Zuber, Meaurement and analysis of lunar basin depths from Clementine altimetry. Icarus
**11**, 107–122 (1998)Google Scholar - J.A. Wood, Bombardment as a cause of the lunar asymmetry. The Moon
**8**, 77–103 (1973)Google Scholar - M.T. Zuber, D.E. Smith, G.A. Neumann, The shape and internal structure of the Moon from the Clementine Mission. Science
**266**, 1839–1843 (1994)Google Scholar - M.T. Zuber, D.E. Smith, G.A. Neumann, Topogrd2, web site of the University of Washington in St. Louis, http://www.wufs.wustl.edu/geodata/clem1-gravity-topo-v1/ (2004)