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  • 1
    Publication Date: 2012-06-23
    Description: Shackleton crater is nearly coincident with the Moon's south pole. Its interior receives almost no direct sunlight and is a perennial cold trap, making Shackleton a promising candidate location in which to seek sequestered volatiles. However, previous orbital and Earth-based radar mapping and orbital optical imaging have yielded conflicting interpretations about the existence of volatiles. Here we present observations from the Lunar Orbiter Laser Altimeter on board the Lunar Reconnaissance Orbiter, revealing Shackleton to be an ancient, unusually well-preserved simple crater whose interior walls are fresher than its floor and rim. Shackleton floor deposits are nearly the same age as the rim, suggesting that little floor deposition has occurred since the crater formed more than three billion years ago. At a wavelength of 1,064 nanometres, the floor of Shackleton is brighter than the surrounding terrain and the interiors of nearby craters, but not as bright as the interior walls. The combined observations are explicable primarily by downslope movement of regolith on the walls exposing fresher underlying material. The relatively brighter crater floor is most simply explained by decreased space weathering due to shadowing, but a one-micrometre-thick layer containing about 20 per cent surficial ice is an alternative possibility.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zuber, Maria T -- Head, James W -- Smith, David E -- Neumann, Gregory A -- Mazarico, Erwan -- Torrence, Mark H -- Aharonson, Oded -- Tye, Alexander R -- Fassett, Caleb I -- Rosenburg, Margaret A -- Melosh, H Jay -- England -- Nature. 2012 Jun 20;486(7403):378-81. doi: 10.1038/nature11216.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. zuber@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722197" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2012-03-23
    Description: Radio tracking of the MESSENGER spacecraft has provided a model of Mercury's gravity field. In the northern hemisphere, several large gravity anomalies, including candidate mass concentrations (mascons), exceed 100 milli-Galileos (mgal). Mercury's northern hemisphere crust is thicker at low latitudes and thinner in the polar region and shows evidence for thinning beneath some impact basins. The low-degree gravity field, combined with planetary spin parameters, yields the moment of inertia C/MR(2) = 0.353 +/- 0.017, where M and R are Mercury's mass and radius, and a ratio of the moment of inertia of Mercury's solid outer shell to that of the planet of C(m)/C = 0.452 +/- 0.035. A model for Mercury's radial density distribution consistent with these results includes a solid silicate crust and mantle overlying a solid iron-sulfide layer and an iron-rich liquid outer core and perhaps a solid inner core.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, David E -- Zuber, Maria T -- Phillips, Roger J -- Solomon, Sean C -- Hauck, Steven A 2nd -- Lemoine, Frank G -- Mazarico, Erwan -- Neumann, Gregory A -- Peale, Stanton J -- Margot, Jean-Luc -- Johnson, Catherine L -- Torrence, Mark H -- Perry, Mark E -- Rowlands, David D -- Goossens, Sander -- Head, James W -- Taylor, Anthony H -- New York, N.Y. -- Science. 2012 Apr 13;336(6078):214-7. doi: 10.1126/science.1218809. Epub 2012 Mar 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22438509" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2013-06-01
    Description: High-resolution gravity data from the Gravity Recovery and Interior Laboratory spacecraft have clarified the origin of lunar mass concentrations (mascons). Free-air gravity anomalies over lunar impact basins display bull's-eye patterns consisting of a central positive (mascon) anomaly, a surrounding negative collar, and a positive outer annulus. We show that this pattern results from impact basin excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool. We used a hydrocode to simulate the impact and a self-consistent finite-element model to simulate the subsequent viscoelastic relaxation and cooling. The primary parameters controlling the modeled gravity signatures of mascon basins are the impactor energy, the lunar thermal gradient at the time of impact, the crustal thickness, and the extent of volcanic fill.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Melosh, H J -- Freed, Andrew M -- Johnson, Brandon C -- Blair, David M -- Andrews-Hanna, Jeffrey C -- Neumann, Gregory A -- Phillips, Roger J -- Smith, David E -- Solomon, Sean C -- Wieczorek, Mark A -- Zuber, Maria T -- New York, N.Y. -- Science. 2013 Jun 28;340(6140):1552-5. doi: 10.1126/science.1235768. Epub 2013 May 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, USA. jmelosh@purdue.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23722426" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2012-12-12
    Description: Spacecraft-to-spacecraft tracking observations from the Gravity Recovery and Interior Laboratory (GRAIL) have been used to construct a gravitational field of the Moon to spherical harmonic degree and order 420. The GRAIL field reveals features not previously resolved, including tectonic structures, volcanic landforms, basin rings, crater central peaks, and numerous simple craters. From degrees 80 through 300, over 98% of the gravitational signature is associated with topography, a result that reflects the preservation of crater relief in highly fractured crust. The remaining 2% represents fine details of subsurface structure not previously resolved. GRAIL elucidates the role of impact bombardment in homogenizing the distribution of shallow density anomalies on terrestrial planetary bodies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zuber, Maria T -- Smith, David E -- Watkins, Michael M -- Asmar, Sami W -- Konopliv, Alexander S -- Lemoine, Frank G -- Melosh, H Jay -- Neumann, Gregory A -- Phillips, Roger J -- Solomon, Sean C -- Wieczorek, Mark A -- Williams, James G -- Goossens, Sander J -- Kruizinga, Gerhard -- Mazarico, Erwan -- Park, Ryan S -- Yuan, Dah-Ning -- New York, N.Y. -- Science. 2013 Feb 8;339(6120):668-71. doi: 10.1126/science.1231507. Epub 2012 Dec 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA. zuber@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23223395" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2014-10-04
    Description: The Procellarum region is a broad area on the nearside of the Moon that is characterized by low elevations, thin crust, and high surface concentrations of the heat-producing elements uranium, thorium, and potassium. The region has been interpreted as an ancient impact basin approximately 3,200 kilometres in diameter, although supporting evidence at the surface would have been largely obscured as a result of the great antiquity and poor preservation of any diagnostic features. Here we use data from the Gravity Recovery and Interior Laboratory (GRAIL) mission to examine the subsurface structure of Procellarum. The Bouguer gravity anomalies and gravity gradients reveal a pattern of narrow linear anomalies that border Procellarum and are interpreted to be the frozen remnants of lava-filled rifts and the underlying feeder dykes that served as the magma plumbing system for much of the nearside mare volcanism. The discontinuous surface structures that were earlier interpreted as remnants of an impact basin rim are shown in GRAIL data to be a part of this continuous set of border structures in a quasi-rectangular pattern with angular intersections, contrary to the expected circular or elliptical shape of an impact basin. The spatial pattern of magmatic-tectonic structures bounding Procellarum is consistent with their formation in response to thermal stresses produced by the differential cooling of the province relative to its surroundings, coupled with magmatic activity driven by the greater-than-average heat flux in the region.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Andrews-Hanna, Jeffrey C -- Besserer, Jonathan -- Head, James W 3rd -- Howett, Carly J A -- Kiefer, Walter S -- Lucey, Paul J -- McGovern, Patrick J -- Melosh, H Jay -- Neumann, Gregory A -- Phillips, Roger J -- Schenk, Paul M -- Smith, David E -- Solomon, Sean C -- Zuber, Maria T -- England -- Nature. 2014 Oct 2;514(7520):68-71. doi: 10.1038/nature13697.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geophysics and Center for Space Resources, Colorado School of Mines, Golden, Colorado 80401, USA. ; Department of Earth and Planetary Sciences, University of California, Santa Cruz, California 95064, USA. ; Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA. ; Planetary Science Directorate, Southwest Research Institute, Boulder, Colorado 80302, USA. ; Lunar and Planetary Institute, Houston, Texas 77058, USA. ; Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, Hawaii 96822, USA. ; Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA. ; Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. ; Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA. ; 1] Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20015, USA [2] Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25279919" target="_blank"〉PubMed〈/a〉
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    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2012-03-23
    Description: Laser altimetry by the MESSENGER spacecraft has yielded a topographic model of the northern hemisphere of Mercury. The dynamic range of elevations is considerably smaller than those of Mars or the Moon. The most prominent feature is an extensive lowland at high northern latitudes that hosts the volcanic northern plains. Within this lowland is a broad topographic rise that experienced uplift after plains emplacement. The interior of the 1500-km-diameter Caloris impact basin has been modified so that part of the basin floor now stands higher than the rim. The elevated portion of the floor of Caloris appears to be part of a quasi-linear rise that extends for approximately half the planetary circumference at mid-latitudes. Collectively, these features imply that long-wavelength changes to Mercury's topography occurred after the earliest phases of the planet's geological history.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zuber, Maria T -- Smith, David E -- Phillips, Roger J -- Solomon, Sean C -- Neumann, Gregory A -- Hauck, Steven A 2nd -- Peale, Stanton J -- Barnouin, Olivier S -- Head, James W -- Johnson, Catherine L -- Lemoine, Frank G -- Mazarico, Erwan -- Sun, Xiaoli -- Torrence, Mark H -- Freed, Andrew M -- Klimczak, Christian -- Margot, Jean-Luc -- Oberst, Jurgen -- Perry, Mark E -- McNutt, Ralph L Jr -- Balcerski, Jeffrey A -- Michel, Nathalie -- Talpe, Matthieu J -- Yang, Di -- New York, N.Y. -- Science. 2012 Apr 13;336(6078):217-20. doi: 10.1126/science.1218805. Epub 2012 Mar 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. zuber@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22438510" target="_blank"〉PubMed〈/a〉
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    Electronic ISSN: 1095-9203
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  • 7
    Publication Date: 2012-12-01
    Description: Measurements of surface reflectance of permanently shadowed areas near Mercury's north pole reveal regions of anomalously dark and bright deposits at 1064-nanometer wavelength. These reflectance anomalies are concentrated on poleward-facing slopes and are spatially collocated with areas of high radar backscatter postulated to be the result of near-surface water ice. Correlation of observed reflectance with modeled temperatures indicates that the optically bright regions are consistent with surface water ice, whereas dark regions are consistent with a surface layer of complex organic material that likely overlies buried ice and provides thermal insulation. Impacts of comets or volatile-rich asteroids could have provided both dark and bright deposits.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Neumann, Gregory A -- Cavanaugh, John F -- Sun, Xiaoli -- Mazarico, Erwan M -- Smith, David E -- Zuber, Maria T -- Mao, Dandan -- Paige, David A -- Solomon, Sean C -- Ernst, Carolyn M -- Barnouin, Olivier S -- New York, N.Y. -- Science. 2013 Jan 18;339(6117):296-300. doi: 10.1126/science.1229764. Epub 2012 Nov 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉NASA Goddard Space Flight Center, Code 698, Greenbelt, MD 20771, USA. gregory.a.neumann@nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23196910" target="_blank"〉PubMed〈/a〉
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    Electronic ISSN: 1095-9203
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  • 8
    Publication Date: 2012-12-12
    Description: The earliest history of the Moon is poorly preserved in the surface geologic record due to the high flux of impactors, but aspects of that history may be preserved in subsurface structures. Application of gravity gradiometry to observations by the Gravity Recovery and Interior Laboratory (GRAIL) mission results in the identification of a population of linear gravity anomalies with lengths of hundreds of kilometers. Inversion of the gravity anomalies indicates elongated positive-density anomalies that are interpreted to be ancient vertical tabular intrusions or dikes formed by magmatism in combination with extension of the lithosphere. Crosscutting relationships support a pre-Nectarian to Nectarian age, preceding the end of the heavy bombardment of the Moon. The distribution, orientation, and dimensions of the intrusions indicate a globally isotropic extensional stress state arising from an increase in the Moon's radius by 0.6 to 4.9 kilometers early in lunar history, consistent with predictions of thermal models.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Andrews-Hanna, Jeffrey C -- Asmar, Sami W -- Head, James W 3rd -- Kiefer, Walter S -- Konopliv, Alexander S -- Lemoine, Frank G -- Matsuyama, Isamu -- Mazarico, Erwan -- McGovern, Patrick J -- Melosh, H Jay -- Neumann, Gregory A -- Nimmo, Francis -- Phillips, Roger J -- Smith, David E -- Solomon, Sean C -- Taylor, G Jeffrey -- Wieczorek, Mark A -- Williams, James G -- Zuber, Maria T -- New York, N.Y. -- Science. 2013 Feb 8;339(6120):675-8. doi: 10.1126/science.1231753. Epub 2012 Dec 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geophysics and Center for Space Resources, Colorado School of Mines, Golden, CO 80401, USA. jcahanna@mines.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23223393" target="_blank"〉PubMed〈/a〉
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    Electronic ISSN: 1095-9203
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  • 9
    Publication Date: 2012-12-01
    Description: Thermal models for the north polar region of Mercury, calculated from topographic measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, show that the spatial distribution of regions of high radar backscatter is well matched by the predicted distribution of thermally stable water ice. MESSENGER measurements of near-infrared surface reflectance indicate bright surfaces in the coldest areas where water ice is predicted to be stable at the surface, and dark surfaces within and surrounding warmer areas where water ice is predicted to be stable only in the near subsurface. We propose that the dark surface layer is a sublimation lag deposit that may be rich in impact-derived organic material.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paige, David A -- Siegler, Matthew A -- Harmon, John K -- Neumann, Gregory A -- Mazarico, Erwan M -- Smith, David E -- Zuber, Maria T -- Harju, Ellen -- Delitsky, Mona L -- Solomon, Sean C -- New York, N.Y. -- Science. 2013 Jan 18;339(6117):300-3. doi: 10.1126/science.1231106. Epub 2012 Nov 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA. dap@moon.ucla.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23196905" target="_blank"〉PubMed〈/a〉
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  • 10
    Publication Date: 2012-12-12
    Description: High-resolution gravity data obtained from the dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft show that the bulk density of the Moon's highlands crust is 2550 kilograms per cubic meter, substantially lower than generally assumed. When combined with remote sensing and sample data, this density implies an average crustal porosity of 12% to depths of at least a few kilometers. Lateral variations in crustal porosity correlate with the largest impact basins, whereas lateral variations in crustal density correlate with crustal composition. The low-bulk crustal density allows construction of a global crustal thickness model that satisfies the Apollo seismic constraints, and with an average crustal thickness between 34 and 43 kilometers, the bulk refractory element composition of the Moon is not required to be enriched with respect to that of Earth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wieczorek, Mark A -- Neumann, Gregory A -- Nimmo, Francis -- Kiefer, Walter S -- Taylor, G Jeffrey -- Melosh, H Jay -- Phillips, Roger J -- Solomon, Sean C -- Andrews-Hanna, Jeffrey C -- Asmar, Sami W -- Konopliv, Alexander S -- Lemoine, Frank G -- Smith, David E -- Watkins, Michael M -- Williams, James G -- Zuber, Maria T -- New York, N.Y. -- Science. 2013 Feb 8;339(6120):671-5. doi: 10.1126/science.1231530. Epub 2012 Dec 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Physique du Globe de Paris, Sorbonne Paris Cite, Universite Paris Diderot, Case 7071, Lamarck A, 5, rue Thomas Mann, 75205 Paris Cedex 13, France. wieczor@ipgp.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23223394" target="_blank"〉PubMed〈/a〉
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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