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With a total mass similar to the main asteroid belt, the jovian Trojan asteroids are a major feature in the Solar System. Based upon the thermal infrared spectra of the largest Trojans obtained with the Spitzer space telescope, Emery et al. (Emery, J.P., Cruikshank, D.P., van Cleve, J. [2006]. Icarus 182, 496) suggested that the surfaces of these Trojans may consist of fine-grained silicates suspended...
We compare the altitude of three O 2 night airglow emissions observed at the limb of Venus by the VIRTIS spectral imager with those values predicted by a model accounting for the different radiative lifetimes and collisional deactivation of the upper O 2 states. The O and CO 2 density profiles are based on remote sensing observations from the Venus Express spacecraft. Effective...
We have made photoacoustic measurements for the ν 4 bending mode lifetime in methane in self collision over a temperature range of 146–293K. We analyzed these results through a new theory using finite differences. Via a numerical transient analysis and a statistical evaluation of data we obtained similar results as those of earlier experimenters. Having proved the capabilities of our equipment...
We present high-resolution infrared spectroscopic measurements of the ecliptic Comet 2P/Encke, observed on 4–6 November 2003 during its close approach to the Earth, using the Near Infrared Echelle Spectrograph on the Keck II telescope. We present flux-calibrated spectra, production rates, and mixing ratios for H 2 O, CH 3 OH, HCN, H 2 CO, C 2 H 2 , C 2 ...
The unlit side of the dense B ring of Saturn does not receive direct sunlight. Yet it cools down as the Sun sets on the ring from solstice to equinox. A multi-scale thermal model that treats the heat transfer through a packed ensemble of particles is built to study the orbital and seasonal temperature variations of both lit and unlit sides of this opaque ring. Heat transfer by radiation, conduction...
The Cassini mission has investigated Titan’s upper atmosphere in detail and found that, under solar irradiation, it has a well-developed ionosphere, which peaks between 1000 and 1200km. In this paper we focus on the T40, T41, T42 and T48 Titan flybys by the Cassini spacecraft and use in situ measurements of N 2 and CH 4 densities by the Ion Neutral Mass Spectrometer (INMS) as input...
We model Titan’s lakes and seas as methane–ethane–nitrogen systems and model the buoyancy of solids in these systems assuming thermodynamic equilibrium. We find that ice will float in methane-rich lakes for all temperatures below the freezing point of pure methane and that ice will also float in ethane-rich seas provided the ice has an air porosity of greater than 5% by volume.
We present evidence that the failure to account for proper motion is responsible for most of the regional biases seen in the astrometry of asteroids produced by the Pan-STARRS sky survey, as well as the 0.02arcsec northward bias seen in our own Apophis astrometry.
For the geochemical investigation of extraterrestrial surfaces laser-induced breakdown spectroscopy (LIBS) has been suggested as a powerful analytical tool, and is part of the payload on NASA’s rover Curiosity, which reached Mars in August 2012. Apart from soil in general, LIBS is capable of analyzing ice and salts within the soil. This study demonstrates the feasibility of LIBS for investigating...
Schrödinger Basin provides a window into the stratigraphy of the lunar crust adjacent to the South Pole-Aitken Basin region that we have probed with Lunar Reconnaissance Orbiter, Moon Mineralogy Mapper (M 3 ), and crater-scaling relationships. The composition of materials that make up the basin wall, impact melt, and peak ring provide a cross-section of the lunar crust, which reveals products...
A new wavelength-dependent model for CH 4 photolysis branching ratios is proposed, based on the values measured recently by Gans et al. (Gans, B. et al. [2011]. Phys. Chem. Chem. Phys. 13, 8140–8152). We quantify the impact of this representation on the predictions of a photochemical model of Titan’s atmosphere, on their precision, and compare to earlier representations. Although the observed...
We present the first globally complete inventory of permanent shadows on the lunar surface that are detectable with the current global instrument datasets, including discovery of regions with persistent shadows over geologic time periods as close to the equator as ±58° of latitude. These results were obtained through application of a ray tracing technique to the latest global topographic datasets...
A model for the formation and distribution of sedimentary rocks on Mars is proposed. In this model (ISEE-Mars), the rate-limiting step is supply of liquid water from seasonal melting of snow or ice. The model is run for a O(10 2 ) mbar pure CO 2 atmosphere, dusty snow, and solar luminosity reduced by 23%. For these conditions snow melts only near the equator, when obliquity and eccentricity...
We have recently developed a coupled chemistry-emission model for the green (5577Å) and red-doublet (6300, 6364Å) emissions of atomic oxygen on Comet C/1996 B2 Hyakutake. In the present work we applied our model to Comet C/1995 O1 Hale-Bopp, which had an order of magnitude higher H 2 O production rate than Comet Hyakutake, to evaluate the photochemistry associated with the production and loss...
Europa, a satellite of Jupiter, is one of the most intriguing worlds in the Solar System. Its dearth of impact craters and plethora of surface morphologies point to a dynamic evolution of its icy shell in geologically recent times. Double ridges are a common landform and appear to have formed over a significant fraction of the satellite’s observed geologic history. Thus, understanding their formation...
The majority of extraterrestrial particles entering Earth’s atmosphere originate from the Sporadic Meteoroid Complex (SMC) and are associated with many mesospheric layer phenomena. The Meteoroid Input Function (MIF) is a model that has been developed with the purpose of understanding the temporal and spatial variability of the meteoroid impact in the atmosphere. The MIF has been shown to accurately...
Observations of Mercury’s spin rate do not rule out that, in addition to the forced 88-day mantle libration induced by solar torques, a decadal timescale libration may also be present. It has been proposed that this signal represents an amplified forced libration caused by the periodic 11.86yr perturbation on Mercury’s orbit by Jupiter. Here, we investigate the possibility that a decadal libration...
The redistribution of a finite amount of martian surface dust during global dust storms and in the intervening periods has been modelled in a dust lifting version of the UK Mars General Circulation Model. When using a constant, uniform threshold in the model’s wind stress lifting parameterisation and assuming an unlimited supply of surface dust, multiannual simulations displayed some variability in...
Interior to the orbit of Mercury, between 0.07 and 0.21AU, is a dynamically stable region where a population of asteroids, known as Vulcanoids, may reside. We present the results from our search for Vulcanoids using archival data from the Heliospheric Imager-1 (HI-1) instrument on NASA’s two STEREO spacecraft. Four separate observers independently searched through images obtained from 2008-12-10 to...
Precession of the orbit poles and spin poles for triaxial bodies, including the possibility of phase locking, is addressed here. We provide a simple derivation of the time-averaged gravitational potential and associated torque, thereby confirming the results of Gladman et al. (Gladman, B., Quinn, D., Nicholson, P., Rand, R. [1996]. Icarus 122, 166–192).
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