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V-P. Kostama, M. Aittola, J. Raitala (University of Oulu)
The terms ``arachnoid" and ``nova" (``spider" and ``new" in Latin) are used for a special group of Venusian structures with circular-radial and stellate fracture patterns, respectively. Although arachnoids and novae clearly differ from each other, many earlier studies have classified them to belong to the same class of corona-like features. While they may somehow reflect certain corona-like formation phases, either as subtypes of coronae or stages of corona development, our studies show, that these three, coronae, arachnoids, and novae, should be considered separately.
All these features have typical and very different morphologies, extents of volcanism and distributions on Venus. Based on the morphologies of the features, these terms are very descriptive to the structural formations in question. Even if the basic morphologies are rather simple, the main differences between all arachnoids and novae make them clearly distinctive from each other in an amount which allows both of them to be classified into several subtypes based on their own characteristics.
The terms ``arachnoid" and ``nova" are short and their definitions in the Venusian context are well established. If taken too literally, the terms may cause some confusion, but they have survived long enough time to be exactly as acceptable as is the term ``corona". Actually, these short descriptive terms can be favored as long as there are not any generic terms to state the phenomena actually essential for their formation. These simple terms are convenient, readily characterize the specified features, and can be successfully used for further classification and characterization studies.
Acknowledgements: We would like to thank the Finnish Academy for providing funds for the study.