Coronae on Venus: Morphology, classification, and distribution
1990; Elsevier BV; Volume: 87; Issue: 2 Linguagem: Inglês
10.1016/0019-1035(90)90148-3
ISSN1090-2643
Autores Tópico(s)Methane Hydrates and Related Phenomena
ResumoTwo major types of circular features with no direct morphologic analog on the terrestrial planets were identified in Venera 1516 radar images of Venus: coronae and corona-like features. Coronae are irregular to circular structures characterized by a complex interior zone and maximum widths of 170–690 km. Corona-like features resemble coronae but lack an annulus of ridges. Twenty-one structures that fit the definition of coronae have been identified in Venera 1516 coverage, along with eleven corona-like features. Each group has been subdivided into three classes based on general morphology. Symmetrical coronae are characterized by circular to oval form, with interiors characterized by flows, domes, and tectonic ridges. Asymmetrical coronae have similar morphology, but have only a partial annulus or are asymmetrical about a central axis. Subdued coronae are dominated by smooth plains, with flooded and embayed annuli. Double corona-like structures are composed of two linked rings and are found along ridge belts in the region east of Atalanta Planitia. Irregular corona-like features are surrounded by a rim rather than an annulus, as are the Double structures, and are very subdued in appearance. Heart-shaped corona-like features are rounded at one end and form a wedge at the other end. We interpret the classes of coronae and corona-like features to have a similar mode of origin, with differences in morphology due to the stage of evolution and/or varying amounts and significance of geologic processes (i.e., tectonism, volcanism, gravitational relaxation) that occur during their evolution. Corona evolution is characterized by early uplift and volcanism, followed by annulus formation. Formation of a peripheral trough may occur in the middle to late stages of corona evolution, followed by extensive volcanism and lowering of topographic relief. Both coronae and corona-like features are interpreted to have formed as a result of uplift and volcanism caused by a thermal anomaly at depth, followed by gravitational relaxation.
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