ABSTRACT
Hyperion, Saturn's eighth largest icy satellite, is a body of irregular shape in a state of chaotic rotation. The surface is segregated into two distinct units. A spatially dominant high-albedo unit having the strong signature of H2O ice contrasts with a unit that is about a factor of four lower in albedo and is found mostly in the bottoms of cup-like craters. Here we report observations of Hyperion's surface in the ultraviolet and near-infrared spectral regions with two optical remote sensing instruments on the Cassini spacecraft at closest approach during a fly-by on 25-26 September 2005. The close fly-by afforded us the opportunity to obtain separate reflectance spectra of the high- and low-albedo surface components. The low-albedo material has spectral similarities and compositional signatures that link it with the surface of Phoebe and a hemisphere-wide superficial coating on Iapetus.
ABSTRACT
Spatially resolved infrared and ultraviolet wavelength spectra of Europa's leading, anti-jovian quadrant observed from the Galileo spacecraft show absorption features resulting from hydrogen peroxide. Comparisons with laboratory measurements indicate surface hydrogen peroxide concentrations of about 0.13 percent, by number, relative to water ice. The inferred abundance is consistent with radiolytic production of hydrogen peroxide by intense energetic particle bombardment and demonstrates that Europa's surface chemistry is dominated by radiolysis.
Subject(s)
Extraterrestrial Environment , Hydrogen Peroxide/analysis , Jupiter , Hydrogen Peroxide/chemistry , Ice , Spectrophotometry, Infrared , Spectrophotometry, Ultraviolet , Water/chemistryABSTRACT
This paper reviews the major clinical and radiographic features of sialoliths and illustrates these with an unusual case of multiple sialoliths within the submandibular gland duct. The differential diagnosis of other calcific structures both within and outside the salivary gland that may mimic a sialolith is also presented.
Subject(s)
Salivary Duct Calculi/pathology , Submandibular Gland Diseases/pathology , Female , Humans , Middle Aged , Salivary Duct Calculi/surgery , Submandibular Gland Diseases/surgeryABSTRACT
Chronic recurrent multifocal osteomyelitis (CRMO) is an aseptic inflammatory disorder of unknown cause occurring in children and adolescents. It is characterized by multifocal bone lesions with pain and swelling recurring over months to years. Lesions usually involve the metaphyses of the long bones and involvement of the jaw is rare. The clinical presentation, radiographic appearance and histology of a case of CRMO involving the mandible in an 8-year-old girl are documented. The radiographic appearance of another three cases is also described.