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Planetary science: Explaining Earth–Moon similarity *IMAGES* (N&V) NATURE Planetary science Embargo London: Wednesday 08 April 2015 18:00 (BST) New York: Wednesday 08 April 2015 13:00 (EDT) Tokyo: Thursday 09 April 2015 02:00 (JST) Sydney: Thursday 09 April 2015 03:00 (AEST) The planetary body that collided with the early Earth to produce the Moon may have had an Earth-like composition, reports a paper published in Nature this week. The study could resolve a long-standing challenge in understanding the origin of the Moon. The Moon is thought to have formed from a collision between the growing Earth and a Marssized body. From the majority of numerical simulations of this ‘giant impact’, it seems that most of the material that formed the Moon would have come from the impactor itself rather than the proto-Earth. However, rock samples from the Moon reveal a similar composition to Earth’s mantle, which has posed a major challenge to this model of Moon formation, given that other bodies in the Solar System have different compositions. Alessandra Mastrobuono-Battisti and colleagues simulated collisions between protoplanets and compared the composition of each surviving planet with the composition of its last giant impactor. They found that 20 to 40 per cent of impactors had similar compositions to the planets they impacted, whereas planets that formed in the same simulation tended to have distinct compositions. The authors suggest that their results may explain the compositional similarities between the Earth and the Moon — and why their compositions differ from those of other planets in the Solar System. Article and author details 1. A primordial origin for the compositional similarity between the Earth and the Moon Corresponding Author Alessandra Mastrobuono-Battisti Israel Institute of Technology, Haifa, Israel Email: [email protected], Tel: +972 04829 5909 News & Views Author Robin Canup Southwest Research Institute, Boulder, Colorado, United States Email: [email protected] DOI 10.1038/nature14333 Online paper* http://nature.com/articles/doi:10.1038/nature14333 * Please link to the article in online versions of your report (the URL will go live after the embargo ends). Image Caption: A collision between two planetary bodies of similar composition leading to the formation of the Moon. Credit: Hagai Perets Planetary science: Understanding the early history of the Earth–Moon system NATURE Planetary science Embargo London: Wednesday 08 April 2015 18:00 (BST) New York: Wednesday 08 April 2015 13:00 (EDT) Tokyo: Thursday 09 April 2015 02:00 (JST) Sydney: Thursday 09 April 2015 03:00 (AEST) Differences between tungsten isotope measurements of the Earth and the Moon, reported in two papers published in this week’s Nature, provide evidence to support theories that, following the giant Moon-forming impact, a ‘late veneer’ of material was added to both bodies. Previous measurements were unable to distinguish between the tungsten isotope compositions of the Earth and the Moon, and the differences now reported provide information about the early history of the Earth–Moon system that may affect models of the Moon’s formation. The Earth’s crust and mantle have an excess of iron-loving elements, such as tungsten, which has prompted suggestions that the iron-loving elements now measured on the Earth and Moon come mainly from a ‘late veneer’ of material that accumulated after the giant Moon-forming impact (and therefore were not incorporated into the Earth’s core). If this theory is true, the Earth and Moon are expected to have different tungsten compositions, but the expected difference has thus far eluded detection. Such differences have now been identified by two independent studies. Analyses of lunar rocks performed by Thomas Kruijer and co-authors and Mathieu Touboul and colleagues reveal an excess in the abundance of the tungsten isotope 182W on the Moon relative to the present-day Earth’s mantle. The offset is best explained by differing proportions of material accumulated by each object after the Moon-forming impact, which supports the late veneer hypothesis. Article and author details 1. Lunar tungsten isotopic evidence for the late veneer Corresponding Author Thomas Kruijer Westfälische Wilhelms-Universität Münster, Münster, Germany Email: [email protected], Tel: +49 174 62 80574 DOI 10.1038/nature14360 Online paper* http://nature.com/articles/doi:10.1038/nature14360 2. Tungsten isotopic evidence for disproportional late accretion to the earth and moon Corresponding Author Mathieu Touboul Université Lyon, Lyon, France Email: [email protected], Tel: +33 6 17 50 53 18 DOI 10.1038/nature14355 Online paper* http://nature.com/articles/doi:10.1038/nature14355 * Please link to the article in online versions of your report (the URL will go live after the embargo ends).
