Icarus
The several relativistic observables in the lunar orbit measureable by present-day lunar laser ranging data are analytically calculated in a unified treatment. Because the solar tidal deformation of the lunar orbit plays such a central role in altering amplitudes and frequencies in the lunar motion, the relativistic equations of motion are solved using procedures similar to those G. W. Hill introduced...
Chondrules represent a significant mass fraction of primitive meteorites. These millimeter-sized glassy droplets appear to be the products of intensive transient heating events. Their size distribution, chemical and mineral composition, texture, and isotope composition suggest that chondrules were produced as a result of short duration melting followed by rapid cooling of solid precursor particles...
Deimos may be largely uniform in density. We find here the gravitational field of Deimos and its moments of inertia from the moon's shape and an assumed uniform density distribution. From these data we compute the expected orientation. The orientation of the model Deimos relative to Mars agrees with that observed to within the observation uncertainties (a few degrees). Hence Deimos may be homogeneous...
With this paper we complete our review on the dynamics in mean motion resonances. Here we investigate the 4/1, 3/1, 5/2, and 7/3 commensurabilities and show that, due to the interaction between the v 5 and v 6 secular resonances, chaotic motion is present almost everywhere in the phase space. This chaotic motion is responsible for the large jumps in the eccentricity (up to 0.8 or more)...
We have modeled the far-infrared spectrum of Titan between 200 and 600 cm -1 , including the fine structure of the H 2 -N 2 and H 2 -CH 4 dimers around 355 and 585 cm -1 respectively. A selection of 373 Voyager IRIS spectra recorded at low and mid-latitudes provides the observational basis for our analysis. The opacity model is significantly improved...
Wrinkle ridges in the Lunae Planum region of Mars formed in response to compressional stresses associated with the development of the Tharsis rise. In this study, we investigate the accomodation of lithospheric strain associated with wrinkle ridge development in order to constrain the depth penetration of deformation associated with the formation of Tharsis. Using observations that indicate that the...
Modeling the volume of impact melt and its variation with the size of the impact event indicates that, for similar-sized final craters, venusian impacts create about 25% more impact melt than terrestrial impacts. More significantly, venusian impacts result in approximately a factor of three more impact melt than lunar events producing equivalent-sized craters. This difference is due to the higher...
Six IRAS spectra between 7.7 and 23 μm of the comets Tempel 1 and Tempel 2 were retrieved from the LRS raw data for the period July 12-Aug 23, 1983. The 12-μm IRAS survey images revealed that they were slightly extended. All of the spectra are consistent with blackbody radiation near the radiative equilibrium temperatures. No silicate emission is seen.
The effects of solar perturbations on the postcapture orbital behavior of satellites are investigated in the context of the restricted, circular three-body problem as applied to Neptune, Triton, and the Sun. Highly eccentric and inclined satellite orbits are considered; thus a numerical, phenomenological approach is taken to describe variations of the satellite's orbital elements. We focus on harmonic...
Recent studies of the upper atmosphere of Jupiter and the H Lyman α bulge in particular have prompted us to reevaluate Voyager UVS measurements of Jupiter's He 584 Å dayglow. We employ more sophisticated data reduction techniques than for earlier analyses to better quantify the UVS observations. We model Jupiter's He 584 Å intensity using partial frequency redistribution and inhomogeneous atmospheric...
A significant fraction of the solar EUV photons, with energies of up to 6 eV, penetrates the martian atmosphere and interacts with the surface of the planet. Photoelectrons are emitted with a mean kinetic energy of 0.4 eV and their flux, averaged over 1 martian day, is on the order of 10 11 -10 12 m -2 sec -1 at a latitude of 50°N. These electrons are collisionally...
A new non-LTE radiative transfer model has been applied to study the radiative cooling and heating rates induced by the infrared emissions in the martian atmosphere. The cooling rate produced by the CO 2 15-μm bands, for the revised COSPAR mean reference temperature and recent values for CO 2 -O( 3 P) collisions, is very large in the upper mesosphere and thermosphere, reaching...
Extinction efficiency from UV to FIR wavelengths were measured for two kinds of γ-alumina particles; one is commercially available aerosil corundum particles, and the other is a combustion product. It is shown that the spectra showed very broad peaks around 13 μm and that the features agreed very well with those of the spectrum calculated using data of bulk amorphous γ-alumina. Complex refractive...
Infrared photometry at 1.2, 1.6, and 2.2 μm (JHK) is reported for 56 asteroids in the Eos, Koronis and, Maria dynamical families. These data are consistent with a similar surface composition for all of the asteroids of each family. The infrared colors within each family cluster in the region observed for the S taxonomic class, but Eos asteroids may belong to a separable K class. Asteroid 243 Ida,...
Using kinetic data, we have estimated the racemization half-lives and times for total racemization of amino acids under conditions relevant to the surface of Mars. Amino acids from an extinct martian biota maintained in a dry, cold (<250 K) environment would not have racemized significantly over the lifetime of the planet. Racemization would have taken place in environments where liquid water was...
An analysis of thermal profiles and dynamics over a wide range of latitudes for the venusian atmosphere between 70 and 90 km is presented based on high spatial resolution infrared spectra of the night side obtained by the near infrared mapping spectrometer (NIMS) experiment during the Galileo-Venus encounter in February 1990. Using the 4.3-μm CO 2 absorption band, the temperature profile is...
Models of planet formation and of the orbital stability of planetary systems are used to predict the variety of planetary and satellite systems that may be present within our galaxy. A new approximate global criterion for orbital stability of planetary systems based on an extension of the local resonance overlap criterion is proposed. This criterion implies that at least some of Uranus' small inner...
The tropospheric methane molar fraction ( C H 4 . t ) and the ortho/para hydrogen ratio are derived for Uranus and Neptune based on new determinations of spectroscopic parameters for key hydrogen features as reported by D. W. Ferguson et al. (1993, J. Mol. Spec. 160, 315-325). For each planet, the relatively weak laboratory linestrengths (approximately 30 and 15% less than...
Galileo-based models for the shape of 951 Gaspra and the global-average photometric behavior of its surface have been used to model a representative subset of the asteroid's telescopic lightcurves. Fitting the synthetic lightcurves to the observed timing of lightcurve extrema, and knowing the orientation of Gaspra's axes at the time of the Galileo flyby, leads to a sidereal rotation period for the...