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A new laboratory-generated chemical compound made from photodissociated ammonia (NH3) molecules reacting with acetylene (C2H2) was suggested as a possible coloring agent for Jupiter’s Great Red Spot (GRS) by Carlson et al. (2016, Icarus 274, 106–115). Baines et al. (2016, Icarus, submitted) showed that the GRS spectrum measured by the visual channels of the Cassini VIMS instrument in 2000 could be...
The high altitude of Jupiter's Great Red Spot (GRS) may enhance the upward flux of gaseous ammonia (NH3) into the high troposphere, where NH3 molecules can be photodissociated and initiate a chain of chemical reactions with downwelling acetylene molecules (C2H2). These reactions, experimentally studied earlier by (Ferris and Ishikawa [1987] Nature 326, 777-778) and (Ferris and Ishikawa [1988] J. Amer...
An exceptional deposit covering an area of ∼7700km2, displaying morphology indicative of an originally fluid material, occurs near 42.2°N, 167.4°E on the lunar farside. The material occurs as smooth, flat deposits (here termed “ponds”) on the bottoms of many craters and in other topographic depressions, as well as a veneer across the majority of the region. Within this area, the ponded deposits and...
Vesta is a unique, intermediate class of rocky body in the Solar System, between terrestrial planets and small asteroids, because of its size (average radius of ∼263km) and differentiation, with a crust, mantle and core. Vesta’s low surface gravity (0.25m/s 2 ) has led to the continual absence of a protective atmosphere and consequently impact cratering and impact-related processes are prevalent...
The Vesta gravity field and related physical parameters have been precisely measured using 10-months of radiometric Doppler and range data and optical landmark tracking from the Dawn spacecraft. The gravity field, orientation parameters, landmark locations, and Vesta’s orbit are jointly estimated. The resulting spherical harmonic gravity field has a half-wavelength resolution of 42km (degree 20)....
A 20th degree ellipsoidal harmonic gravity field of Vesta is determined by processing radiometric Doppler and range data from the Dawn mission. The gravity field shows sensitivity up to degree 18 and the coefficients are globally determined on average to degree 15. Gravity anomalies are mapped to the Brillouin ellipsoid (304×289×247-km), which is a substantially closer fit to the surface than the...
We present laboratory results on the loss of H 2 O 2 in solid H 2 O+H 2 O 2 mixtures at temperatures between 21 and 145K initiated by UV photolysis (193nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5μm infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with...
Hydrated silica-rich materials have recently been discovered on the surface of Mars by the Mars Exploration Rover (MER) Spirit, the Mars Reconnaissance Orbiter (MRO) Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), and the Mars Express Observatoire pour la Minéralogie, l’Eau, les Glaces, et l’Activité (OMEGA) in several locations. Having been interpreted as hydrothermal deposits and aqueous...
The Rosetta spacecraft flew by Asteroid (2867) Steins on 5 September 2008, allowing the onboard OSIRIS cameras to collect the first images of an E-type asteroid. We implemented several three-dimensional reconstruction techniques to retrieve its shape. Limb profiles, combined with stereo control points, were used to reconstruct an approximate shape model. This model was refined using a stereophotoclinometry...
We report laboratory studies on the 0.8MeV proton irradiation of ices composed of sulfuric acid (H 2 SO 4 ), sulfuric acid monohydrate (H 2 SO 4 ·H 2 O), and sulfuric acid tetrahydrate (H 2 SO 4 ·4H 2 O) between 10 and 180K. Using infrared spectroscopy, we identify the main radiation products as H 2 O, SO 2 , (S 2...
We present a Monte Carlo (MC) model of [OI] 6300Å and [SII] 6716Å emission from Io entering eclipse. The simulation accounts for the 3-D distribution of SO 2 , O, SO, S, and O 2 in Io’s atmosphere, several volcanic plumes, and the magnetic field around Io. Thermal electrons from the jovian plasma torus are input along the simulation domain boundaries and move along the magnetic field...
We present radiative transfer modelling of thermal emission from the nightside of Venus in two ‘spectral window’ regions at 1.51 and 1.55 μm. The first discovery of these windows, reported by Erard et al. [Erard, S., Drossart, P., Piccioni, G., 2009. J. Geophys. Res. Planets 114, doi:10.1029/2008JE003116. E00B27], was achieved using a principal component analysis of data from the VIRTIS instrument...
The effect of density inhomogeneity on the YORP effect for a given shape model is investigated. A density inhomogeneity will cause an offset between the center of figure and the center of mass and a re-orientation of the principal axes away from those associated with the shape alone. Both of these effects can alter the predicted YORP rate of change in angular velocity and obliquity. We apply these...
Using the high-quality data set of 165 images taken at 11 epochs over the 5.13 h rotation of the large C-type Asteroid 511 Davida, we find the dimensions of its triaxial ellipsoid model to be 357±2×294±2×231±50 km. The images were acquired with the adaptive optics system on the 10 m Keck II telescope on December 27, 2002. The a and b diameters are much better determined than previously estimated from...
Spectra of Europa, Ganymede, and Callisto reveal surfaces dominated by frozen water, hydrated materials, and minor amounts of SO 2 , CO 2 , and H 2 O 2 . These icy moons undergo significant bombardment by jovian magnetospheric radiation (protons, electrons, and sulfur and oxygen ions) which alters their surface compositions. In order to understand radiation-induced...
The effect of solar radiation on the near-term rotation rate of Asteroid Itokawa via the YORP effect is predicted using the detailed shape model, rotation pole, mass estimate, and optical properties derived from the Hayabusa mission to Itokawa. Based on these estimates Itokawa is decelerating at a rate which will halve its rotation rate in only 50–90 thousand years, a large deceleration that should...
We present infrared absorption studies on the effects of 50–100 keV Ar + and 100 keV H + ion irradiation of water ice films at 20–120 K. The results support the view that energetic ions can produce hydrogen peroxide on the surface of icy satellites and rings in the outer Solar System, and on ice mantles on interstellar grains. The ion energies are characteristic of magnetospheric ions...
Sulfuric acid hydrate has been proposed as an important species on Europa's surface, the acid being produced by radiolysis of surficial sulfur compounds. We investigated the spectral properties of disordered and crystalline forms of sulfuric acid and suggest that the hydration properties of Europa's hypothesized sulfuric acid lie between two end members: liquid sulfuric acid and its higher crystalline...
We present in this Keck AO paper the first global high angular resolution observations of Io in three broadband near-infrared filters: Kc (2.3 μm), Lp (3.8 μm), and Ms (4.7 μm). The Keck AO observations are composed of 13 data sets taken during short time intervals spanning 10 nights in December, 2001. The MISTRAL deconvolution process, which is specifically aimed for planetary images, was applied...
The 5-μm window in the spectrum of Jupiter is one of the few regions that gives access to the vertical structure of the troposphere between pressure levels of approximately 4 and 8 bar. Voyager/IRIS spectra obtained in 1979 during the Voyager flybys have been analyzed intensively over the past two decades. Most of these analyses concluded on a vertical cloud structure consisting of three layers: an...
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