Japan Geoscience Union Meeting 2014

Presentation information

Print

International Session (Oral)

Symbol P (Space and Planetary Sciences) » P-PS Planetary Sciences

[P-PS02_28AM1] Mars

Mon. Apr 28, 2014 9:00 AM - 10:45 AM 418 (4F)

Convener:*Takehiko Satoh(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), Masaki Ishiwatari(Department of Cosmosciences, Graduate school of Science, Hokkaido University), Ayako Matsuoka(Research Division for Space Plasma, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), Yoshiyuki O. Takahashi(Center for Planetary Science), Sho Sasaki(Department of Earth and Space Sciences, School of Science, Osaka University), Hideaki Miyamoto(The University Museum, The University of Tokyo), Chair:Masaki Ishiwatari(Department of Cosmosciences, Graduate school of Science, Hokkaido University)

9:25 AM - 9:50 AM

★ [PPS02-02] New evidence for plate tectonism on Mars: Accreted Terrains

*James DOHM1, Shigenori MARUYAMA1 (1.Earth-Life Science Institute, Tokyo Institute of Technology)

Keywords:Plate tectonics, accretional complex, OPS

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.