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Two global issues regarding Europa are addressed by a survey of strike-slip faults. First, a common type of terrain that appears to represent convergent sites of surface removal, which may help compensate for substantial widespread dilation along tectonic bands elsewhere, thus helping resolve the problem of conserving global surface area, is identified. Second, evidence for polar wander may provide...
The biological fertilities of planetary materials can be assessed using microcosms based on meteorites. This study applies microcosm tests to martian meteorites and analogues and to carbonaceous chondrites. The biological fertilities of these materials are rated based on the soluble electrolyte nutrients, the growth of mesophile and cold-tolerant algae, and plant tissue cultures. The results show...
We present visible-wavelength (0.435-0.925 μm) spectroscopic measurements for 1341 main-belt asteroids observed during the second phase of the Small Main-belt Asteroid Spectroscopic Survey (SMASSII). The purpose of this survey is to provide a new basis for studying the compositional structure of the asteroid belt. Through the large sample size and the relatively high spectral resolution (R~100) of...
The changing size and aspect ratio of the Great Red Spot from 1880 to 2000 are reviewed, indicating that the length of the system has decreased significantly over the last 100 years and continues to decrease at present at a rate of 0.19 degrees per year. Voyager IRIS maps of para hydrogen fraction and potential temperature over the system are presented, showing the internal structure and surrounding...
This paper reports the results of experiments on projectile impact into regolith targets at various impact angles. Copper projectiles of 240 mg are accelerated to 197 to 272 m s -1 using an electromagnetic gun. The ejecta are detected by thin Al foil targets as secondary targets, and the resulting holes on the foil are measured to derive the spatial distribution of the ejecta. The ejecta...
The goal of this work is to determine the spectroscopic properties of sulfate in martian soil analogs over the wavelength range 0.3 to 25 μm (which is relevant to existing and planned remotely sensed data sets for Mars). Sulfate is an abundant component of martian soil (up to 9% SO 3 by weight) and apparently exists as a particulate in the soil but also as a cement. Although previous studies...
Photometric observations of 1999 HF 1 reveal that its lightcurve has two components of low amplitudes (0.10-0.12 mag) and different periods (2.3191 and 14.02 h). It is likely another binary near-Earth asteroid; its lower limit on the secondary-to-primary-diameter ratio is ~0.2, the radius of the mutual orbit is (2.0+/-0.3)x the effective primary diameter, the primary's bulk density is >2...
If the recently observed young gullies on Mars represent seeps or outflows of aqueous fluid, that fluid must be highly concentrated brine to be even moderately stable under current martian surface conditions. Such brines are to be expected in the megaregolith if an initial saline hydrosphere underwent evapoconcentration via water escape from the atmosphere, evolved into subsurface CaCl 2 -enriched...
The issue of whether the Moon has a small metallic core is reexamined in light of new information: improved dynamical modeling, new constraints on core size, and high temperature and pressure metal-silicate partition coefficients. Addressed specifically is the question of whether the Moon's siderophile element budget can be explained by derivation of the Moon from a differentiated impactor or proto-Earth...
A singular feature in planetary atmospheres, the saturnian midnorthern latitude ''ribbon'' wave, was discovered in images obtained during the Voyager 1 and 2 encounters with the planet in 1980 and 1981. Here we present evidence of its first detection 14 years later (about half a Saturn year later) using archived Hubble Space Telescope images. The properties of the recovered wave (latitude location,...
The main rings of Saturn were observed with the Planetary Camera of the WFPC2 instrument on the Hubble Space Telescope (HST) from September 1996 to December 2000 as the ring opening angle to Earth and Sun increased from 4 o to 24 o , with a spread of phase angles between 0.3 o and 6 o at each opening angle. The rings were routinely observed in the five HST wideband...
Recalibrated and geometrically registered multispectral images from the Imager for Mars Pathfinder (IMP) were analyzed using Spectral Mixture Analysis (SMA) and related techniques. SMA models a multispectral image scene as a linear combination of endmember spectra, and anomalous materials which do not fit the model are detected as model residuals. While most of the IMP data studied here are modeled...
A spectrum from 1.2 to 2.5 μm of Uranus' small satellite Miranda obtained in June 1999 reveals strong water-ice signatures. It confirms the existence of a 2.0-μm water feature previously detected on Miranda and shows a strong second broad 1.5-μm water-ice absorption feature. The spectra also reveal a weak absorption band at 1.65 μm that is indicative of crystalline water ice. Reflectance models which...
Solar phase curves between 0.3 o and 6.0 o and color ratios at wavelengths λ=0.336 μm and λ=0.555 μm for Saturn's rings are presented using recent Hubble Space Telescope observations. We test the hypothesis that the phase reddening of the rings is less due to collective properties of the ring particles than to the individual properties of the ring particles. We use a modified Drossart...
We present absolute abundances and latitudinal variations of ozone and water in the atmosphere of Mars during its late northern spring (L s =67.3 o ) shortly before aphelion. Long-slit maps of the a 1 Δ g state of molecular oxygen (O 2 ) and HDO, an isotopic form of water, were acquired on UT January 21.6 1997 using a high-resolution infrared spectrometer (CSHELL)...
The total mass of the asteroid belt is estimated from an analysis of the motions of the major planets by processing high precision measurements of ranging to the landers Viking-1, Viking-2, and Pathfinder (1976-1997). Modeling of the perturbing accelerations of the major planets accounts for individual contributions of 300 minor planets; the total contribution of all remaining small asteroids is modeled...
The second phase of the Small Main-belt Asteroid Spectroscopic Survey (SMASSII) produced an internally consistent set of visible-wavelength charge-coupled device (CCD) spectra for 1447 asteroids (Bus and Binzel 2002, Icarus, ). These data provide a basis for developing a new asteroid taxonomy that utilizes more of the information contained in CCD spectra. Here we construct a classification system...
Previous modeling by Banaszkiewicz et al. (2000a,b) showed that the CH 4 thermospheric mixing ratio on Titan could vary as much as 35-40% due to ion-neutral chemical reactions. A new vertical methane profile has been computed by simultaneously modifying the stratospheric methane mixing ratio and the K(z) previously considered by Lara et al. (1996) and Banaszkiewicz et al. (2000a,b). A satisfactory...
Using the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal light at optical wavelengths over elongations of 3 ε 30 o from the Sun. This surface brightness map is then used to infer the spatial distribution of interplanetary dust over heliocentric distances of about 10 solar radii to the orbit of Venus. The averaged ecliptic surface brightness...
The analysis of radar observations of the asteroid 4179 Toutatis by Hudson and Ostro (1995, Science270, 84-86) yielded a complex spin state. We revisit the visible lightcurve data on Toutatis (Spencer et al. 1995, Icarus117, 71-89) to explore the feasibility of using a rotational lightcurve to recover the signature of an excited spin state. For this, we apply Fourier transform and CLEAN algorithm...
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