Katarina Miljković^1,*, Mark A. Wieczorek¹, Gareth S. Collins², Matthieu Laneuville¹, Gregory A. Neumann³, H. Jay Melosh⁴, Sean C. Solomon^5,6, Roger J. Phillips⁷, David E. Smith⁸, Maria T. Zuber⁸

¹Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Case 7011, Lamarck A, 5, 35 rue Hélène Brion, 75205 Paris cedex 13, France.
²Department of Earth Sciences and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
³Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
⁴Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA.
⁵Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.
⁶Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA.
⁷Planetary Science Directorate, Southwest Research Institute, Boulder, CO 80302, USA.
⁸Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Maps of crustal thickness derived from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission revealed more large impact basins on the nearside hemisphere of the Moon than on its farside. The enrichment in heat-producing elements and prolonged volcanic activity on the lunar nearside hemisphere indicate that the temperature of the nearside crust and upper mantle was hotter than that of the farside at the time of basin formation. Using the iSALE-2D hydrocode to model impact basin formation, we found that impacts on the hotter nearside would have formed basins with up to twice the diameter of similar impacts on the cooler farside hemisphere. The size distribution of lunar impact basins is thus not representative of the earliest inner solar system impact bombardment.

Reference
Miljković K, Wieczorek MA, Collins GS, Laneuville M, Neumann GA, Melosh HJ, Solomon SC, Phillips RJ, Smith DE and Zuber MT (2013) Asymmetric Distribution of Lunar Impact Basins Caused by Variations in Target Properties. Science 342:724-726.
[doi:10.1126/science.1243224]
Reprinted with permission from AAAS

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