09:25 〜 09:50
★ [PPS02-02] 火星におけるプレートテクトニクス存否の証拠：付加帯
キーワード：プレートテクトニクス, 付加帯, 海洋プレート層序
Reported evidence for plate tectonism has included spatial association among magnetic anomalies, large (thousands of kilometers long) structures, and highly degraded promontories interpreted to be andesitic domes, thrust faults, folds, structurally-controlled basins, large mountain ranges, and topographic and crustal-thickness-model signatures of structural control (including plate movement) within and along the margin of the northern plains. Significant evidence for an ancient phase of plate tectonism on Mars, newly identified, is accretionary complexes, informed through Earth analogs exquisitely detailed here in Japan. This finding represents a new frontier in the geologic investigation of Mars, bringing greater attention to pre-Tharsis (~> 4.0 Ga) terrains, which record Earth-like conditions. Pre-Tharsis, Earth-like conditions include an active dynamo and plate tectonism, as well as Habitable-Trinity conditions?an ocean, relatively thick atmosphere, and primordial crustal materials enriched in phosphorous, iron, among other elements important to life, all of which interact due to hydrological cycling driven by the Sun. Accreted terrains, which mark major crustal shortening through subduction of oceanic crustal materials and associated accumulation of andesites and granites, could comprise rock records on Mars dating back more than 4.2 Ga. Considering planetary evolution of Mars, largely informed through our understanding of the evolution of Earth, the accretionary complexes are likely to record environmental conditions during a time range of several hundred million years, which includes possible fossil life if initiated and evolved during the extremely ancient (>4.0 Ga) Habitable-Trinity conditions. A prime example of an extremely ancient accretionary complex is located to the west of Claritas rise, southwest margin of the Tharsis superplume. At the meeting we will present evidence of a Martian accretionary complex and discuss the implications of such a significant finding, including highlighting the next phase of geologic investigation of the evolution of Mars and its bearing on Astrobiology.