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We present a theoretical investigation of non-equilibrium condensation of refractory metalsinthe primordial solar nebula, in relation to the origin of ''Fremdlinges'' included inCAIs. Todescribe the nucleation process of grains from vapor, weadopted asemi-phenomenological modelmodified fromthe classical nucleation theoryby the introductionof the second virial coefficient of vapor. This modelachieves...
Io, the innermost Galilean satellite of Jupiter, is a fascinating world. Data taken by Voyager and Galileo instruments have established that it is by far the most volcanic body in the Solar System and suggest that the nature of this volcanism could radically differ from volcanism on Earth. We report on near-IR observations taken in February 2001 from the Earth-based 10-m W. M. Keck II telescope using...
The Mars Orbiter Camera onboard the Mars Global Surveyor has obtained several images of polygonal features in the southern polar region. In images taken during the end of the southern spring, when the surrounding surface is free of the seasonal frost, CO 2 ice still appears to be present within the polygonal troughs. In Earth's polar regions, polygons such as these are indicative of water...
We both test and offer an alternative to a meteoroid bombardment model (M. R. Showalter 1998, Science282, 1099-1102) and suggest that anomalous localized brightenings in the F ring observed by Voyager result from disruptive collisions involving poorly consolidated moonlets, or ''rubble piles.'' This model can also explain the transient events observed during ring plane crossing. We have developed...
Recent work has been concerned with calculating the three-dimensional ion concentrations and Pedersen and Hall conductivities within the auroral region of Jupiter for varying conditions of incident electron precipitation. Using the jovian ionospheric model, we present results that show the auroral ionospheric response to changing the incoming flux of precipitating electrons (for constant initial energy)...
The observed transneptunian binaries, with components of comparable mass and large separations, cannot be the result of collisions in the present dynamical environment of the Kuiper belt. They could be produced by collision of two planetesimals within the sphere of influence of a third body during low-velocity accretion in the solar nebula. Thus, they are primordial.
This paper builds on preliminary work in which numerical simulations of the collisional disruption of large asteroids (represented by the Eunomia and Koronis family parent bodies) were performed and which accounted not only for the fragmentation of the solid body through crack propagation, but also for the mutual gravitational interaction of the resulting fragments. It was found that the parent body...
Haze particles exert a significant influence over the thermodynamics and radiation absorption properties of the Titan haze, as well as its complex organic chemistry. Characterization of both the molecular and the submicrometer components of the haze is therefore vital for understanding the global properties of Titan. We have carried out a Titan tholin synthesis experiment and measured the time variation...
A spectrum of Mars of unprecedented quality was obtained in the range of 904-1183 Å with a spectral resolution of 0.2 Å using the Far Ultraviolet Spectroscopic Explorer. Besides marking the first detection of molecular hydrogen on Mars (Krasnopolsky and Feldman, Science 2001 294, 1914-1917), the spectrum also revealed many emission lines of H, O, N, C, Ar, He, N + , C + , and Ar ...
It was found that certain features in the observed spin vector distribution of main belt asteroids can be explained by the differences in the dynamical spin vector evolution between objects with high and low orbital inclinations. In particular, the deficiency of high-inclination objects whose spin vectors are close to the ecliptic plane can be accounted for.The present spin vector distribution of...
We explore the likelihood that early remains of Earth, Mars, and Venus have been preserved on the Moon in high enough concentrations to motivate a search mission. During the Late Heavy Bombardment, the inner planets experienced frequent large impacts. Material ejected by these impacts near the escape velocity would have had the potential to land and be preserved on the surface of the Moon. Such ejecta...
The proposed existence of magnetic lineations in the Terra Cimmeria and Terra Sirenum regions of Mars was initially explained by Earth-like sea-floor spreading. Here we argue instead that these lineations could have been formed at a convergent plate margin through collision and accretion of terranes. A similar process produced banded magnetic anomalies, similar in geometry and even in size to those...
Kuiper belt objects (KBOs) are generally very faint and cannot in practice be monitored with a well-sampled long-term light curve; so our discovery of the bright KBO 2000 EB 173 offers an excellent opportunity for synoptic studies. We present a well-sampled photometric time series (77 R and 29 V magnitudes on 78 nights) over a 225-day time span centered on the 2001 opposition. The...
Greenhouse warming due to carbon dioxide atmospheres may be responsible for maintaining the early Earth's surface temperature above freezing and may even have allowed for liquid water on early Mars. However, the high levels of CO 2 required for such warming should have also resulted in the formation of CO 2 clouds. These clouds, depending on their particle size, could lead to either...
The results of photometric observations of Centaur object Chiron carried out at the Observatorio do Pico dos Dias (OPD, Brazil), the Estacion Astrofsica de Bosque Alegre (EABA, Argentina), and Complejo Astronomico El Leoncito (CASLEO, Argentina) from 1997 to 2001 are presented here. The analysis of the photometric data shows that the brightness of Chiron reached a minimum value in 1999 and began increasing...
We obtain the size and orbital distributions of near-Earth asteroids (NEAs) that are expected to be in the 1 : 1 mean motion resonance with the Earth in a steady state scenario. We predict that the number of such objects with absolute magnitudes H<18 and H<22 is 0.65+/-0.12 and 16.3+/-3.0, respectively. We also map the distribution in the sky of these Earth coorbital NEAs and conclude that these...
We have numerically computed the orbital evolution of ~10 3 particles representing high-speed ejecta from Gilgamesh, the largest impact basin on Ganymede. The integration includes the four Galilean satellites, Jupiter (including J 2 and J 4 ), Saturn, and the Sun. The integrations last 100,000 years. The particles are ejected at a variety of speeds and directions, with the...
We present a second epoch of Very Large Array Saturn observations taken in February 1997 spanning wavelengths 1.3-21 cm. These observations complement earlier observations at Saturn's autumnal equinox in November 1995. In this epoch, however, we generally have better signal-to-noise ratios and the ring inclination of the present observations was -5.0 o , whereas the previous observations were...
We present a simple, semianalytic model of the vaporization of H 2 O and HDO ice from a comet nucleus. We use this model to show that the flux of HDO relative to H 2 O can be much higher, at times, than would be expected from the D/H ratio in the nuclear ice itself. This effect varies with position in the comet's orbit. It is negligible sufficiently near the Sun but could lead to erroneous...
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