Vadym Kaydash^a, Yuriy Shkuratov^a and Gorden Videen^b

^aAstronomical Institute of Kharkov V.N. Karazin National University, Sumskaya 35, Kharkov 61022, Ukraine
^bSpace Science Institute, 4750 Walnut St. Suite 205, Boulder CO 80301, USA

Images acquired by the Narrow Angle Camera of the Lunar Reconnaissance Orbiter allow phase-ratio imagery of young lunar craters surrounded by dark halos. Such imaging is a new optical remote-sensing technique that is sensitive to the degree of surface roughness. We apply the phase-ratio technique to LRO images of young, dark-halo craters near the crater Denning and in the Balmer basin, in addition to craters created by the impacts of the Ranger-6 spacecraft and Saturn-5 sections of Apollo-13 and Apollo-17. We suggest an alternative explanation of the dark halos and rays seen near the craters at large phase angles. Phase-ratio imaging suggests that these features result from higher surface roughness. Thus, the interpretation of dark crater halos and rays as a composition/maturity variance should be used with caution. The composition and structure factors can be effectively discriminated only using images acquired in a wide range of phase angles including small angles.

Reference
Kaydash V, Yuriy Shkuratov Y and Videen G (in press) Dark halos and rays of young lunar craters: a new insight into interpretation. Icarus
[doi:10.1016/j.icarus.2013.11.025]
Copyright Elsevier

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Humayun M^a et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

^aDepartment of Earth, Ocean and Atmospheric Science, and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA

We still seek a copyright agreement with Nature to display abstracts of their cosmochemistry related publications.

Reference
Humayun M et al. (2013) Origin and age of the earliest Martian crust from meteorite NWA 7533. Nature 503:513–516.
[doi:10.1038/nature12764]

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McSween HY

Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996–1410, USA.

We still seek a copyright agreement with Nature to display abstracts of their cosmochemistry related publications.

Reference
McSween HY (2013) Planetary science: A chunk of ancient Mars. Nature 503:473–474.
[doi:10.1038/nature12836]

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Erik A. Petigura^a,b,*, Andrew W. Howard^b, and Geoffrey W. Marcy^a

^aAstronomy Department, University of California, Berkeley, CA 94720; and
^bInstitute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822

Determining whether Earth-like planets are common or rare looms as a touchstone in the question of life in the universe. We searched for Earth-size planets that cross in front of their host stars by examining the brightness measurements of 42,000 stars from National Aeronautics and Space Administration’s Kepler mission. We found 603 planets, including 10 that are Earth size () and receive comparable levels of stellar energy to that of Earth (). We account for Kepler’s imperfect detectability of such planets by injecting synthetic planet–caused dimmings into the Kepler brightness measurements and recording the fraction detected. We find that 11 ± 4% of Sun-like stars harbor an Earth-size planet receiving between one and four times the stellar intensity as Earth. We also find that the occurrence of Earth-size planets is constant with increasing orbital period (P), within equal intervals of logP up to ∼200 d. Extrapolating, one finds % of Sun-like stars harbor an Earth-size planet with orbital periods of 200–400 d.

Reference
Petigura EA, Howard AW and Marcy GW (in press) Prevalence of Earth-size planets orbiting Sun-like stars. PNAS
[doi:10.1073/pnas.1319909110]

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