H. Kurokawa^a,b, M. Sato^b,c, M. Ushioda^b, T. Matsuyama^b, R. Moriwaki^b, J.M. Dohm^d and T. Usui^b

^aDepartment of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
^bDepartment of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
^cDepartment of Environmental Changes, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
^dEarth-Life-Science Institute, Tokyo Institute of Technology, 2-12-1-1E-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan

Martian surface morphology implies that Mars was once warm enough to maintain persistent liquid water on its surface. While the high D/H ratios (∼6 times the Earth’s ocean water) of the current martian atmosphere suggest that significant water has been lost from the surface during martian history, the timing, processes, and the amount of the water loss have been poorly constrained. Recent technical developments of ion-microprobe analysis of martian meteorites have provided accurate estimation of hydrogen isotope compositions (D/H) of martian water reservoirs at the time when the meteorites formed. Based on the D/H data from the meteorites, this study demonstrates that the water loss during the pre-Noachian (>41–99 m global equivalent layers, GEL) was more significant than in the rest of martian history (>10–53 m GEL). Combining our results with geological and geomorphological evidence for ancient oceans, we propose that undetected subsurface water/ice (≃100–1000 m GEL) should exist, and it exceeds the observable present water inventory (≃20–30 m GEL) on Mars.

Reference
Kurokawa H, Sato M, Ushioda M, Matsuyama T, Moriwaki R, Dohm JM and Usui T (2014) Evolution of water reservoirs on Mars: Constraints from hydrogen isotopes in martian meteorites. Earth and Planetary Science Letters 394:179.
[doi:10.1016/j.epsl.2014.03.027]
Copyright Elsevier

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Mohamad Ali-Dib¹, Olivier Mousis¹, Jean-Marc Petit¹ and Jonathan I. Lunine²

¹Université de Franche-Comté, Institut UTINAM, CNRS/INSU, UMR 6213, Observatoire de Besançon, BP 1615, F-25010 Besançon Cedex, France
²Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA

The C to O ratio is a crucial determinant of the chemical properties of planets. The recent observation of WASP 12b, a giant planet with a C/O value larger than that estimated for its host star, poses a conundrum for understanding the origin of this elemental ratio in any given planetary system. In this paper, we propose a mechanism for enhancing the value of C/O in the disk through the transport and distribution of volatiles. We construct a model that computes the abundances of major C- and O-bearing volatiles under the influence of gas drag, sublimation, vapor diffusion, condensation, and coagulation in a multi-iceline 1+1D protoplanetary disk. We find a gradual depletion in water and carbon monoxide vapors inside the water’s iceline, with carbon monoxide depleting slower than water. This effect increases the gaseous C/O and decreases the C/H ratio in this region to values similar to those found in WASP 12b’s day side atmosphere. Giant planets whose envelopes were accreted inside the water’s iceline should then display C/O values larger than those of their parent stars, making them members of the class of so-called carbon-rich planets.

Reference
Ali-Dib M, Mousis O, Jean-Marc Petit J-M and Lunine JI (2014) Carbon-rich Planet Formation in a Solar Composition Disk. The Astrophysical Journal 785:125.
[doi:10.1088/0004-637X/785/2/125]

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E. Vilenius¹ et al. (>10)*

*Find the extensive, full author and affiliation list on the publishers website.

¹ Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, Giessenbachstr., 85741 Garching, Germany

Context. The Kuiper belt is formed of planetesimals which failed to grow to planets and its dynamical structure has been affected by Neptune. The classical Kuiper belt contains objects both from a low-inclination, presumably primordial, distribution and from a high-inclination dynamically excited population.
Aims. Based on a sample of classical trans-Neptunian objects (TNOs) with observations at thermal wavelengths we determine radiometric sizes, geometric albedos and thermal beaming factors for each object as well as study sample properties of dynamically hot and cold classicals.
Methods. Observations near the thermal peak of TNOs using infrared space telescopes are combined with optical magnitudes using the radiometric technique with near-Earth asteroid thermal model (NEATM). We have determined three-band flux densities fromHerschel/PACS observations at 70.0, 100.0 and 160.0 μm and Spitzer/MIPS at 23.68 and 71.42 μm when available. We use reexamined absolute visual magnitudes from the literature and ground based programs in support of Herschel observations.
Results. We have analysed 18 classical TNOs with previously unpublished data and re-analysed previously published targets with updated data reduction to determine their sizes and geometric albedos as well as beaming factors when data quality allows. We have combined these samples with classical TNOs with radiometric results in the literature for the analysis of sample properties of a total of 44 objects. We find a median geometric albedo for cold classical TNOs of 0.14_-0.07^+0.09 and for dynamically hot classical TNOs, excluding the Haumea family and dwarf planets, 0.085_-0.045^+0.084. We have determined the bulk densities of Borasisi-Pabu (2.1_-1.2^+2.6 g cm^-3), Varda-Ilmarë (1.25_-0.43^+0.40 g cm^-3) and 2001 QC₂₉₈ (1.14_-0.30^+0.34 g cm^-3) as well as updated previous density estimates of four targets. We have determined the slope parameter of the debiased cumulative size distribution of dynamically hot classical TNOs as q = 2.3 ± 0.1 in the diameter range 100 < D < 500 km. For dynamically cold classical TNOs we determineq = 5.1 ± 1.1 in the diameter range 160 < D < 280 km as the cold classical TNOs have a smaller maximum size.

Reference
Vilenius et al. (2014) “TNOs are Cool”: A survey of the trans-Neptunian region – X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations. Astronomy & Astrophysics 564:A35.
[doi:10.1051/0004-6361/201322416]
Reproduced with permission © ESO

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