Showing papers in "Icarus in 1993"

TL;DR: The results suggest that mid-to-early K stars should be considered along with G stars as optimal candidates in the search for extraterrestrial life.

TL;DR: In this article, the authors study the dynamics of a pair of interacting planets orbiting a Sun and find that the system will be Hill stable (that is, stable against close approaches for all time) if the fractional orbital separation Δ > 2.4(μ 1 + μ 2 ) 1/3, where μ 1 and μ 2 are the mass ratios of the two planets to the Sun.

TL;DR: In this article, a systematic spectral analysis has been carried out on a large subset (39 of 144) of the S-type asteroid population, including a number of distinct compositional subtypes which exhibit surface silicate assemblages.

TL;DR: In this article, a model for particle diffusion involving the profile of the nebula gas turbulence and the particle Schmidt number is developed, which is a function of particle size and density.

TL;DR: An earlier investigation of the formation of approximately 10(26) g planetary embryos from much smaller planetesimals has been extended to include the effects of collisional fragmentation, the low relative velocity regime in which the effects due to solar gravity are important, and independent perturbations of eccentricity and inclination.

TL;DR: In this paper, the authors investigated the evolution of random velocities of planetesimals due to scattering by a protoplanet through N-body simulations, and they found that eccentricities em and inclinations im of the planets in the vicinity of the prot-oplanet ("heated region") are increased by the perturbation of the pro-planetet rather than by the planeteimals.

TL;DR: In this paper, a new interpretation for observed opacity indices at submillimeter- and millimeter-wavelength regions of circumstellar disks around T Tauri stars is presented, and the particle growth can explain this difference in observed opacity index without considering any change in composition.

TL;DR: In this paper, the near-IR spectra of the Venus night-side emission are simulated by means of a radiative transfer code that allows for emission, absorption, and scattering by atmospheric gases and particles.

TL;DR: It is estimated that about 1% of the organics found in the coma of Comet Halley could have been produced by thermal formaldehyde reactions taking place in the nucleus.

TL;DR: The juxtaposition of stream valley headwaters with volcanoes and impact craters on Mars strongly implies that subsurface heating of groundwater created thermal springs, and these springs create distinctive geomorphic features and chemical signatures which can be detected by remote sensing.

TL;DR: In this paper, an experimental setup was developed where two millimeter-sized dust aggregates collided in vacuum with relative velocities between ∼0.15 and ∼4 m sec -1.

TL;DR: In this paper, the results of a series of eight experimental hypervelocity impacts of soda lime glass projectiles into porous sintered aggregate glass targets with varying strengths and densities were presented.

TL;DR: In this paper, a discriminant that relies on photoevaporation by Lyman continuum photons of the outer parts of the disk as the primary hydrogen (and helium) loss mechanism was proposed.

TL;DR: In this paper, the authors used the narrow-band International Halley Watch (IHW) filters to observe 13 comets, and showed that the dusty comets in the sample form a separate group.

TL;DR: In this article, the authors presented new photometric measurements of Uranus and Neptune between 0.35 and 2.0 mm, and derived the following empirical fit to the Uranian temperature spectrum, TU(λ), in the 0.34-3.3mm region:TU = ao + a1 [Log10(λ)] + a2 [Log 10(λ] + a 2 [Log 8.5]2 + a3 [Log 7.3]3K, withao = -795.694 a1 = 845.5

TL;DR: In this article, the authors examined the rate of accretion of mass and spin angular momentum by a spherical solid body immersed in a differentially rotating disk of particles, and they derived the mass and angular momentum accretion rates and their scaling with r and s.

TL;DR: In this paper, the first part of the meteorite/NEA delivery process is modeled and assessed in a quantitative way, namely the ejection of fragments from cratering and breakup events undergone by the existing asteroids as a consequence of impacts and the chance insertion of the escaping fragments into the "dangerous" strips of the phase space close to the g = g6 (or v6 ) resonance.

TL;DR: In this article, the authors developed a self-consistent model which agrees with measurements and predicts the density profiles of important photochemical products, including H, H2, and odd nitrogen profiles.

TL;DR: In this article, the hypervelocity impact that excavated the Stickney crater on Phobos is numerically modeled in order to understand the effects this collision had on the interior and surface of Phobos.

TL;DR: In contrast with previous suggestions, the abundance of free, submicrometer "dust" is small throughout the entire A Ring; this conclusion holds even in the outermost A Ring, which is strongly perturbed by density waves as discussed by the authors.

TL;DR: In this paper, the authors detect a gaseous circumstellar disk around a relatively old T Tauri star, GM Aurigae, at 4″ resolution in λ = 1.4-mm continuum emission and in the 13CO (2 → 1) line reveal unresolved and compact dust and gas associated with the stellar position and at the core of a larger rotating Gaseous disk, 950 × 530 AU in extent.

TL;DR: In this article, 50 separate irradiations of a 6:1 mixture of H2O/C2H6 ice conducted over a 5-month period have yielded sufficient tholin for the determination of its physical constants in the 006 to 40 micron range while the imaginary part of the refractive index k was obtained by transmission measurements on thin-film samples and Kramers-Kronig analysis (KKA).

TL;DR: In this article, the authors show that the most natural source of the turbulence in the solar nebula is likely to occur via localized, small but not infinitesimal perturbations of the Keplerian shear, which occur naturally via pressure fluctuations, interactions with planetesimals, or material infall.

TL;DR: In this paper, the GISS GCM was used to examine the hypothesis that equatorial superrotation on slowly rotating planets is sensitive to the nature of the vertical radiative heating profile and can exist in the absence of diurnally varying forcing.

TL;DR: In this paper, the authors investigated the location and the dynamic effects of the three main secular resonances v 5, v 6, and v 16 inside the mean motion commensurabilities.

TL;DR: In this article, the authors used a carefully selected set of observations of five comets along with a vectorial model and the Haser model to explore the lifetimes against photodissociation of H 2 O and OH in cometary comae.

TL;DR: Wetherill et al. as discussed by the authors proposed the Best Bulk Silicate Earth (BBSE) concept, which represents Earth's primitive mantle (modern mantle + crust) and showed the combined effects of core formation and volatility, presumably including condensation and sublimation in the solar nebula and volatile loss during the accretion and early evolution of Earth.

TL;DR: In this article, the orbital dynamics of micrometer-sized dust grains are explored numerically and analytically, treating the strongest perturbation forces acting on close circumplanetary dust grains: higher-order gravity, radiation pressure, and the electromagnetic force.

TL;DR: In this article, the Mie scattering theory was used to obtain the vertical profiles of the volume extinction coefficient at 3.7 and 1.9 μm in the altitude range of 12-35 km.

TL;DR: The influence of gravity on the disposition of loose material on the surfaces of small satellites is investigated using the martian satellites as examples in this paper, where the authors show a strong correlation of indicators of global downslope movement with dynamic height.