The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The tectonically and cryovolcanically resurfaced terrains of Ganymede attest to the satellite's turbulent geologic history. Yet, the ultimate cause of its geologic violence remains unknown. One plausible scenario suggests that the Galilean satellites passed through one or more Laplace-like resonances before evolving into the current Laplace resonance. Passage through such a resonance can excite Ganymede's...
A survey of THEMIS visible wavelength images in the Aeolis/Zephyria Plana region over the two western lobes of the equatorial Medusae Fossae Formation (MFF) shows ∼150 sinuous ridges having a variety of morphologies and contexts. To systematize investigation, we use a classification scheme including both individual ridge and ridge network types, as well as associations with impact craters and fan-shaped...
The Deep Impact mission discovered repetitive outbursts on Comet 9P/Tempel 1 and the presence of several smooth terrains on its surface. We present new measurements of the extent of the smooth terrains, the slopes along their centerlines, and the areas of their likely source regions. Our analysis of these features indicates that they are <700 orbits old and probably the result of an ongoing process...
In this study we compare the sodium exosphere observations made by Schleicher et al. [Schleicher, H., and 4 colleagues, 2004. Astron. Astrophys. 425, 1119–1124] with the result of a detailed numerical simulation. The observations, made during the transit of Mercury across the solar disk on 7 May 2003, show a maximum of sodium emission near the polar regions, with north prevalence, and the presence...
We use a low pressure flame to produce soot by-products as possible analogues of the carbonaceous dust present in diverse astrophysical environments, such as circumstellar shells, diffuse interstellar medium, planetary disks, as well as in our own Solar System. Several soot samples, displaying an initial chemical diversity from aromatic to aliphatic dominated material, are irradiated with 200–400...
Cassini radar observations show that Titan's spin is slightly faster than synchronous spin. Angular momentum exchange between Titan's surface and the atmosphere over seasonal time scales corresponding to Saturn's orbital period of 29.5 year is the most likely cause of the observed non-synchronous rotation. We study the effect of Saturn's gravitational torque and torques between internal layers on...
We report a study on the broadband ultraviolet photolysis of methane–water ice mixtures, at low methane concentrations and temperatures relevant to the icy satellites of the outer Solar System. The photochemistry of these mixtures is dominated by the action of hydroxyl radicals on methane and the resulting products. This implies that, given sufficient exposure time, the methane will eventually be...
When the Atacama Large Millimeter Array (ALMA) is completed, it will synthesize angular resolution as fine as 5 milliarcseconds. With such resolution and ALMA's large number of stations and collecting area, it will be possible to rapidly map the shapes, large-scale surface features, and surface temperature distributions of the 700 largest objects in the main asteroid belt and the hundred largest Jupiter...
The Cassini spacecraft has acquired 25 radar altimeter elevation profiles along Titan's surface as of April 2008, and we have analyzed 18 of these for which there are currently reconstructed ephemeris data. Altimeter measurements were collected at spatial footprint sizes from 6–60 km along ground tracks of length 400–3600 km. The elevation profiles yield topographic information at this resolution...
We report resolved photometry of the primary and secondary components of 23 transneptunian binaries obtained with the Hubble Space Telescope. V–I colors of the components range from 0.7 to 1.5 with a median uncertainty of 0.06 magnitudes. The colors of the primaries and secondaries are correlated with a Spearman rank correlation probability of 99.99991%, 5 sigma for a normal distribution. Fits to...
We observed the 15 August 2007 occultation of the uranian satellite Titania and the 19 August 2007 occultation of Ariel by Umbriel using the Agile high-speed photometer on the APO 3.5 m telescope. We find that the Titania event midpoint occurred at 09:16:39.20 UT and the Ariel event midpoint at 07:59:49.4 UT, which was 26.2 s and 37.4 s later than predicted, respectively. Our best fit impact parameter...
Ultraviolet (UV) spectra of Saturn's aurora obtained with the Hubble Space Telescope Imaging Spectrograph (STIS), the Cassini Ultraviolet Imaging Spectrograph (UVIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE) have been analyzed. Comparisons between the observed spectra and synthetic models of electron-excited H 2 have been used to determine various auroral characteristics. Far ultraviolet...
We have found sorted stone circles and polygons near the equator of Mars, using new 25 cm/pixel NASA HiRISE (High Resolution Imaging Science Experiment) images. The sorted circles occur in geologically recent catastrophic flood deposits in the equatorial Elysium Planitia region, and are diagnostic of periglacial processes: sorted polygons do not form from volcanic activity, as has been suggested for...
The first comprehensive calibration and mapping of the thermal microwave emission from Titan's surface is reported based on radiometric data obtained at 2.2-cm wavelength by the passive radiometer included in the Cassini Radar instrument. The data reported were accumulated from 69 separate observational segments in Titan passes from Ta (October 2004) through T30 (May 2007) and include emission from...
Recent geomorphic, remote sensing, and atmospheric modeling studies have shown evidence for abundant ground ice deposits in the martian mid-latitudes. Numerous potential water/ice-rich flow features have been identified in craters in these regions, including arcuate ridges, gullies, and small flow lobes. Previous studies (such as in Newton Basin) have shown that arcuate ridges and gullies are mainly...
A new analysis of the Lunar Prospector epithermal neutron data is presented, providing an improved map of the distribution of hydrogen near to the lunar poles. This is achieved using a specially developed pixon image reconstruction algorithm to deconvolve the instrumental response of the Lunar Prospector's neutron spectrometer from the observed data, while simultaneously suppressing the statistical...
We study the dynamical evolution of Asteroid 2002 AA 29 . This object moves in the co-orbital region of the Earth and is the first known asteroid which experiences recurrent horseshoe–quasi-satellite transitions. The transitions between the HS and QS states are unique among other known Earth co-orbital asteroids and in the QS state 2002 AA 29 remains very close to Earth (within 0.2...
The infrared AOTF spectrometer is a part of the SPICAM experiment onboard the Mars-Express ESA mission. The instrument has a capability of solar occultations and operates in the spectral range of 1–1.7 μm with a spectral resolution of ∼3.5 cm −1 . We report results from 24 orbits obtained during MY28 at Ls 130°–160°, and the latitude range of 40°–55° N. For these orbits the atmospheric density...
The neutron signals measured by the Neutron Spectrometer on board the Mars Odyssey satellite are analyzed at Central Elysium Planitia. The neutron currents have variations associated with the boundaries of geological units in all three energy ranges: thermal, epithermal and fast neutron. Geochemical constraints can be derived from the neutron data using macroscopic absorption cross sections. This...
The Mars Global Surveyor Thermal Emission Spectrometer (TES) instrument has returned over 200 million thermal infrared spectra of Mars taken between March 1999 and August 2004. This represents one of the most complete records of spatial and temporal changes of the martian atmosphere ever recorded by an orbiting spacecraft. Previous reports of the standard TES retrieval of aerosol optical depth have...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.