Clast fabric and mass wasting on Asteroid 25143-Itokawa: Correlation with talus and other periglacial features on Earth |
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| Authors: | William C Mahaney Volli Kalm Barbara Kapran Kenneth Hewitt |
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| Institution: | aQuaternary Surveys, 26 Thornhill Ave., Thornhill, Ontario, Canada L4J 1J4;bGeography Department, York University, 4700 Keele St., N. York, Ontario, Canada M3J 1P3;cFaculty of Science and Technology, Institute of Ecology and Earth Sciences, Tartu University, 46 Vanemuise Str., Tartu, Estonia, 51014;dDepartment of Geography and Environmental Studies and Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3Z9 |
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| Abstract: | Regolith on Itokawa, a 300-meter diameter near-Earth asteroid, first imaged by the Hayabusa Spacecraft in 2005, provides a new database of information on surface features and different space-form (i.e. landform) assemblages. The satellite imagery was taken from distances of near-surface and 2 km to 63 m, the latter giving image resolutions of 6 mm/pixel. Small regolith-covered asteroids produce rubble-covered surface mantles, resident on slopes ranging from 27° relative to an artificial horizon, and distributed non-uniformly across the surface. Low gravity acceleration on Itokawa means that clast movement is largely the result of global vibrations caused by impacts producing seismic shaking. Gravel-network orientations, previously correlated with imbricated stream gravels on Earth by the Hayabusa Scientific Team (Miyamoto, H., Yano, H., Scheeres, D.J., Abe, S., Barnaouin-Jha, O., Cheng, A.F., Demura, H., Gaskell, R.W., Hirata, N., Ishiguro, M., Michikami, T., Nakamura, A.M., Hakamura, R., Saito, J., Sasaki, S., 2007. Regolith migration and sorting on asteroid Itokawa. Science. 316, 1011–1014, Fig. 2F), are here partly correlated with talus and stone-banked lobe accumulations on Earth. We present ‘sliderock’ accumulations on Itokawa correlated with talus accumulations on Earth from several high, middle and low latitude Cryic localities. The presence of debris-flow accumulated clastic material indicates the presence of permafrost and issuance of meltwater at some time in the past, presumably linked to an orbital or solar radiation perturbation. The available data indicate the presence of water, at least on a punctuated time scale; along with the presence of Fe, the combination of the two suggesting weathering processes and a dynamic surface geology on what was previously considered to be a dry, barren, lifeless world. |
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| Keywords: | Clast fabric analysis Periglacial talus Asteroid regolith Surface geology on 25143-Itokawa |
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