Preface     

Enrique Pérez  Richard de Grijs  Rosa M. González Delgado 《Astrophysics and Space Science》2009,324(2-4):79-81

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A lunar cryptomare dome near Mee H and Drebbel F     

Raffaello Lena  Jim Phillips  Geologic Lunar Research Group 《Planetary and Space Science》2009,57(3):267-275

In this study, we examine the lunar mare dome Mee 1 situated near the craters Mee H and Drebbel F in a region showing evidence of ancient (pre-Orientale) mare volcanism and cryptomare deposits. Regional stratigraphic relations indicate that Mee 1 was formed prior to the Orientale impact at the beginning of the Imbrian period. Based on a combined photoclinometry and shape from shading technique applied to telescopic CCD images of the dome acquired under oblique illumination, we determined a diameter of Mee 1 of 25 km, a height of 250 m, a flank slope of 1.15^°, and a volume of . Based on rheologic modelling of the dome and a viscoelastic model of the feeder dike, we obtained a magma viscosity of , an effusion rate of , a duration of the effusion process of 1.6 years, a magma rise speed of , a width of the feeder dike of 32 m, and a horizontal dike length of 144 km. A comparison of Mee 1 with domes with similar morphometric properties, which are located near Milichius and inside the crater Petavius, reveals strong similarities with respect to the viscosity of the dome-forming magma and the feeder dike geometry, while the effusion rate and magma rise speed of Mee 1 are somewhat higher. The pronounced morphometric differences between Mee 1 and a smaller dome situated close to the crater Doppelmayer and characterised by a similar magma viscosity suggest that the growth of that dome was limited by exhaustion of the magma reservoir, while Mee 1 and the other larger domes display morphometric properties presumably coming closer to the cooling limit. The comparison of the ancient dome Mee 1 with the younger (Eratosthenian) edifices near Milichius and Doppelmayer suggests that the conditions in the upper mantle and the crust favoured high eruption volumes, effusion rates, and magma rise speeds, implying the occurrence of large magma reservoirs preventing the limitation of dome growth by magma exhaustion. On the other hand, we observe similar general morphometric, rheologic, and feeder dike characteristics and, thus, conclude that the formation conditions of lunar mare domes did not change fundamentally during the Imbrian period.  相似文献   

Lander radioscience for obtaining the rotation and orientation of Mars     

Veronique Dehant  William Folkner  Etienne Renotte  Daniel Orban  Sami Asmar  Georges Balmino  Jean-Pierre Barriot  Jeremy Benoist  Richard Biancale  Jens Biele  Frank Budnik  Stefaan Burger  Olivier de Viron  Bernd Häusler  Özgur Karatekin  Sébastien Le Maistre  Philippe Lognonné  Michel Menvielle  Michel Mitrovic  Martin Pätzold  Marie Yseboodt 《Planetary and Space Science》2009,57(8-9):1050-1067

The paper presents the concept, the objectives, the approach used, and the expected performances and accuracies of a radioscience experiment based on a radio link between the Earth and the surface of Mars. This experiment involves radioscience equipment installed on a lander at the surface of Mars. The experiment with the generic name lander radioscience (LaRa) consists of an X-band transponder that has been designed to obtain, over at least one Martian year, two-way Doppler measurements from the radio link between the ExoMars lander and the Earth (ExoMars is an ESA mission to Mars due to launch in 2013). These Doppler measurements will be used to obtain Mars’ orientation in space and rotation (precession and nutations, and length-of-day variations). More specifically, the relative position of the lander on the surface of Mars with respect to the Earth ground stations allows reconstructing Mars’ time varying orientation and rotation in space.Precession will be determined with an accuracy better by a factor of 4 (better than the 0.1% level) with respect to the present-day accuracy after only a few months at the Martian surface. This precession determination will, in turn, improve the determination of the moment of inertia of the whole planet (mantle plus core) and the radius of the core: for a specific interior composition or even for a range of possible compositions, the core radius is expected to be determined with a precision decreasing to a few tens of kilometers.A fairly precise measurement of variations in the orientation of Mars’ spin axis will enable, in addition to the determination of the moment of inertia of the core, an even better determination of the size of the core via the core resonance in the nutation amplitudes. When the core is liquid, the free core nutation (FCN) resonance induces a change in the nutation amplitudes, with respect to their values for a solid planet, at the percent level in the large semi-annual prograde nutation amplitude and even more (a few percent, a few tens of percent or more, depending on the FCN period) for the retrograde ter-annual nutation amplitude. The resonance amplification depends on the size, moment of inertia, and flattening of the core. For a large core, the amplification can be very large, ensuring the detection of the FCN, and determination of the core moment of inertia.The measurement of variations in Mars’ rotation also determines variations of the angular momentum due to seasonal mass transfer between the atmosphere and ice caps. Observations even for a short period of 180 days at the surface of Mars will decrease the uncertainty by a factor of two with respect to the present knowledge of these quantities (at the 10% level).The ultimate objectives of the proposed experiment are to obtain information on Mars’ interior and on the sublimation/condensation of CO₂ in Mars’ atmosphere. Improved knowledge of the interior will help us to better understand the formation and evolution of Mars. Improved knowledge of the CO₂ sublimation/condensation cycle will enable better understanding of the circulation and dynamics of Mars’ atmosphere.  相似文献   

On the Temporal Variability of the “Strahl” and Its Relationship with Solar Wind Characteristics: STEREO SWEA Observations     

P. Louarn  C. Diéval  V. Génot  B. Lavraud  A. Opitz  A. Fedorov  J. A. Sauvaud  D. Larson  A. Galvin  M. H. Acuňa  J. Luhmann 《Solar physics》2009,259(1-2):311-321

The “strahl” is a specific population of the solar wind, constituted by strongly field aligned electrons flowing away from the Sun, with energies >60 eV. Using the Solar Wind Electron Analyzer (SWEA) onboard STEREO, we investigate the short time scale fluctuations of this population. It is shown that its phase space density (PSD) at times presents fluctuations larger than 50% at scales of the order of minutes and less. The fluctuations are particularly strong for periods of a few tens of hours in high-speed streams, following the crossing of the corotating interaction region, when the strahl is also the most collimated in pitch angle. The amplitude of the fluctuations tends to decrease in conjunction with a broadening in pitch angle. Generally, the strongly fluctuating strahl is observed when the magnetic field is also highly perturbed. That SWEA is able to perform a very rapid 3D analysis at a given energy is essential since it can be demonstrated that the observed magnetic turbulence can only marginally perturb the PSD measurements.  相似文献   

TNOs are Cool: A Survey of the Transneptunian Region     

Thomas G. Müller  Emmanuel Lellouch  Hermann Böhnhardt  John Stansberry  Antonella Barucci  Jacques Crovisier  Audrey Delsanti  Alain Doressoundiram  Elisabetta Dotto  René Duffard  Sonia Fornasier  Olivier Groussin  Pedro J. Gutiérrez  Olivier Hainaut  Alan W. Harris  Paul Hartogh  Daniel Hestroffer  Jonathan Horner  Dave Jewitt  Mark Kidger  Csaba Kiss  Pedro Lacerda  Luisa Lara  Tanya Lim  Michael Mueller  Raphael Moreno  Jose-Luis Ortiz  Miriam Rengel  Pablo Santos-Sanz  Bruce Swinyard  Nicolas Thomas  Audrey Thirouin  David Trilling 《Earth, Moon, and Planets》2009,105(2-4):209-219

Over one thousand objects have so far been discovered orbiting beyond Neptune. These trans-Neptunian objects (TNOs) represent the primitive remnants of the planetesimal disk from which the planets formed and are perhaps analogous to the unseen dust parent-bodies in debris disks observed around other main-sequence stars. The dynamical and physical properties of these bodies provide unique and important constraints on formation and evolution models of the Solar System. While the dynamical architecture in this region (also known as the Kuiper Belt) is becoming relatively clear, the physical properties of the objects are still largely unexplored. In particular, fundamental parameters such as size, albedo, density and thermal properties are difficult to measure. Measurements of thermal emission, which peaks at far-IR wavelengths, offer the best means available to determine the physical properties. While Spitzer has provided some results, notably revealing a large albedo diversity in this population, the increased sensitivity of Herschel and its superior wavelength coverage should permit profound advances in the field. Within our accepted project we propose to perform radiometric measurements of 139 objects, including 25 known multiple systems. When combined with measurements of the dust population beyond Neptune (e.g. from the New Horizons mission to Pluto), our results will provide a benchmark for understanding the Solar debris disk, and extra-solar ones as well.  相似文献   

A Multi-Wavelength Simultaneous Study of the Composition of the Halley Family Comet 8P/Tuttle     

E. Jehin  D. Bockelée-Morvan  N. Dello Russo  J. Manfroid  D. Hutsemékers  H. Kawakita  H. Kobayashi  R. Schulz  A. Smette  J. Stüwe  M. Weiler  C. Arpigny  N. Biver  A. Cochran  J. Crovisier  P. Magain  H. Rauer  H. Sana  R. J. Vervack  H. Weaver  J.-M. Zucconi 《Earth, Moon, and Planets》2009,105(2-4):343-349

We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very Large Telescope. Such multi-wavelength and coordinated observations are a good example of what can be done to support space missions. From high resolution optical spectroscopy of the CN (0,0) 388 nm and NH₂ (0,9,0) 610 nm bands using UVES at UT2 we determined ¹²C/¹³C = 90 ± 10 and ¹⁴N/¹⁵N = 150 ± 20 in CN and we derived a nuclear spin temperature of NH₃ of 29 ± 1 K. These values are similar to those found in Oort-Cloud and Jupiter Family comets. From low resolution long slit spectroscopy with FORS1 at UT2 we determined the CN, C₃ and C₂ production rates and the parent and daughter scale lengths up to 5.2 10⁵ km tailward. From high resolution IR spectroscopy with CRIRES at UT1 we measured simultaneously the production rates and mixing ratios of H₂O, HCN, C₂H₂, CH₄, C₂H₆, and CH₃OH.  相似文献   

Ground-Based Observations of the Martian Atmosphere in Support of Space Missions     

Thérèse Encrenaz 《Earth, Moon, and Planets》2009,105(2-4):127-134

Although Mars is a favored target for planetary exploration, there is still a need for complementary ground-based observing programs of the Martian atmosphere, and this need will remain in the future. Indeed, as the atmosphere is very tenuous (less than 0.01 bar at the surface), the lines are very narrow and a high spectral resolving power (above 10⁴) is required over large spectral intervals. In addition, ground-based observations of Mars allow the instantaneous mapping of the whole planet, and thus the study of diurnal effects, which cannot be achieved from an orbiter. Recent ground-based achievements about the Martian atmospheric science include the first detection of H₂O₂ in the submillimeter range, the measurement of winds from CO millimetric transitions, the first detection of CH₄ and the O₃, H₂O₂, H₂O, and CH₄ mapping in the infrared. With an ELT, it will be possible to study at high spatial resolution transient atmospheric phenomena and to search for traces of minor constituents with unprecedented sensitivity. With ALMA, it will be also possible to search for minor species and to map the mesospheric winds for better constraining the climate models.  相似文献   

Duality properties of Gorringe–Leach equations     

Yves Grandati  Alain Bérard  Hervé Mohrbach 《Celestial Mechanics and Dynamical Astronomy》2009,103(2):133-141

In the category of motions preserving the angular momentum direction, Gorringe and Leach exhibited two classes of differential equations having elliptical orbits. After enlarging slightly these classes, we show that they are related by a duality correspondence of the Arnold–Vassiliev type. The specific associated conserved quantities (Laplace–Runge–Lenz vector and Fradkin–Jauch–Hill tensor) are then dual reflections of each other.  相似文献   

The unusual interacting pair of galaxies IC 3481 and IC 3481A: An optical-NIR photometric and spectroscopic analysis     

J.A. Pérez Grana  S.N. Kemp  E. de la Fuente  A.C. Katsiyannis  J. Meaburn 《New Astronomy》2009,14(6):556-566

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Optical spectroscopy of V1123 Tauri and its visual companion     

Carlos M. Gutiérrez 《New Astronomy》2009,14(2):149-151

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