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Every year the Earth crosses or passes near one of the dust trails left by Comet 55P/Tempel–Tuttle in its pass through the Solar System every 33.2 years. This produces a meteor shower Commonly called the Leonid. The 2001 Leonid meteor shower is one of the strongest in recent years. We present observations made by the 50 MHz all-sky meteor radar located at the Platteville Atmospheric Observatory in...
In 2006, Earth encountered a trail of dust left by Comet 55P/Tempel-Tuttle two revolutions ago, in A.D. 1932. The resulting Leonid shower outburst was observed by low light level cameras from locations in Spain. The outburst peaked on 2006 Nov. 19d 04h39m ± 3m UT (predicted: 19d 04h50m ± 15m UT), with a FWHM of 43 ± 10 min (predicted: 38 min), at a peak rate of ZHR=80±10/h (predicted: 50–200 per hour)...
The obliquity of Titan is small, but certainly non-zero, and may be used to place constraints on Titan's internal structure. The measured gravity coefficients of Titan imply that it is non-hydrostatic and thus the normal Darwin–Radau approach to determining internal structure cannot be applied. However, if the obliquity is assumed to be tidally damped (that is, in a Cassini state) then combining the...
In a previous publication [Brasser, R., Duncan, M.J., Levison, H.F., 2006. Icarus 184, 59–82], models of the inner Oort cloud were built which included the effect of an embedded star cluster on cometary orbits about the Sun. The main conclusions of that paper were that the formation efficiency is about 10% and the median distance of the cloud to the Sun only depends on the mean density of gas and...
Titan's haze, formed by photolysis of C 2 H 2 , C 2 H 4 and HCN, was found experimentally to trap Ar, Kr and Xe with efficiencies of 3.5 × 10 −4 , 1.9 × 10 −3 and 6.5 × 10 −2 [noble gas atom]/[carbon atom] in the polymer, respectively. The rate of aerosol formation and settling down of 3 × 10 −13 kg m −2 s −1 , as inferred...
Arnus Vallis (AV) is a >300-km-long sinuous, rille located on the northeastern flank of the Syrtis Major volcano on Mars. Observational evidence presented here suggests that AV formed as an open lava channel that was at least partly incised into the pre-existing terrain. The lava source area consists of a sub-circular pit at the southwestern end of a 7-km-long straight section of channel. AV trends...
Comet 73P-B/Schwassmann–Wachmann 3 was observed with IRCS/Subaru at geocentric distance of 0.074 AU on UT 10 May 2006. Multiple H 2 O emission lines were detected in non-resonant fluorescence near 2.9 μm. No significant variation in total H 2 O production rate was found during the (3 h) duration of our observations. H 2 O rotational temperatures and ortho-to-para abundance...
We present the results of a visible spectroscopic survey of igneous asteroids belonging to the small and intriguing E-class, including 2867 Steins, a target of the Rosetta mission. The survey was carried out at the 3.5 m Telescopio Nazionale Galileo (TNG), and at the 3.5 m New Technology Telescope (NTT) of the European Southern Observatory. We obtained new visible spectra for eighteen E-type asteroids,...
The Cassini Titan Radar Mapper observed on Titan several large features interpreted as cryovolcanic during the October 26, 2004 pass at high northern latitudes [Lopes, R.M.C., and 43 colleagues, 2007. Icarus 186, 395–412]. To date, models of ammonia-water resurfacing have not been tied to specific events or evolutionary stages of Titan. We propose a model of cryovolcanism that involves cracking at...
We present quantitative laboratory studies that simulate the effect of redeposition of impact-ejecta on mineral surfaces. We produced deposits of natural olivine (Fo90) and forsterite on olivine and forsterite powder samples by ns-pulsed laser ablation. The deposits produce changes in the optical reflectance (0.66–2.5 μm). We show that significant darkening and reddening of the surface occurs when...
The past 4 decades of Mars exploration have provided much information about the Mars surface, when its interior structure remains relatively poorly constrained. Today available data are compatible with a large range of model parameters. Seismology is able to provide valuable additional data but the number of seismographs will likely be quite limited, specially in the early-stage of future Mars seismic...
We explore the origin and orbital evolution of the Kuiper belt in the framework of a recent model of the dynamical evolution of the giant planets, sometimes known as the Nice model. This model is characterized by a short, but violent, instability phase, during which the planets were on large eccentricity orbits. It successfully explains, for the first time, the current orbital architecture of the...
The discovery of the chaotic behavior of the planetary orbits in the Solar System [Laskar, J., 1989. Nature 338, 237–238; Laskar, J., 1990. Icarus 88, 266–291] was obtained using numerical integration of averaged equations. In [Laskar, J., 1994. Astron. Astrophys. 287, L9–L12], these same equations are integrated over several Gyr and show the evidence of very large possible increase of the eccentricity...
Five years of meteor orbit data from CMOR (the Canadian Meteor Orbit Radar) are used to study the high-resolution orbital structure of the sporadic meteoroid complex. The large number of high quality orbits (2.35 million) allows the orbital characteristics of meteoroids to be studied not only in the five sporadic sources accessible from the latitude of London, Ontario, Canada, but at a resolution...
We report laboratory experiments and modeling calculations investigating the effect of a hydrocarbon coating on ammonia ice spectral signatures. Observational evidence and thermochemical models indicate an abundance of ammonia ice clouds in Jupiter's atmosphere. However, spectrally identifiable ammonia ice clouds are found covering less than 1% of Jupiter's atmosphere, notably in areas of strong vertical...
In 2003, we initiated a long-term Adaptive Optics campaign to study the orbit of various main-belt asteroidal systems. Here we present a consistent solution for the mutual orbits of four binary systems: 22 Kalliope, 45 Eugenia, 107 Camilla and 762 Pulcova. With the exception of 45 Eugenia, we did not detect any additional satellites around these systems although we have the capability of detecting...
Near-infrared brightness temperature contrasts observed on the night side of Venus indicate variations in the size and distribution of particles in the lower and middle cloud decks. McGouldrick and Toon [McGouldrick, K., Toon, O.B., 2007. Icarus 191, 1–24] have shown that these changes can be explained by large-scale dynamics; in particular, that downdrafts may produce optical depth “holes” in the...
Numerical simulations of jovian vortices at tropical and temperate latitudes, under different atmospheric conditions, have been performed using the EPIC code [Dowling, T.E., Fisher, A.S., Gierasch, P.J., Harrington, J., LeBeau, R.P., Santori, C.M., 1998. Icarus 132, 221–238] to simulate the high-resolution observations of motions and of the lifetimes presented in a previous work [Legarreta, J., Sánchez-Lavega,...
Acid weathering of plagioclase–pyroxene mixtures has been investigated with an open system kinetic dissolution model. The modeling reveals that elevated plagioclase/pyroxene ratios observed in some low-albedo martian regions and atmospheric dust could be partially caused by preferential dissolution of pyroxenes at pHs below ∼3–4. Surface materials with smaller grain sizes, affected by lower pH fluids,...
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