Joseph S. Levy , Thomas F. Subak , Ian Armstrong , Izzy King , Lingfeng Kuang , Lily Kuentz , James H. Gearon , Sophie Naylor , M.C. Rapoza , Haobo Wang
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引用次数: 0
Abstract
The interlocking plateaus of martian chaotic terrain have long been inferred to relate to Hesperian outflow-channel megafloods. Numerous hypotheses have been invoked to explain the formation of the hundreds-of-kilometer-scale depressions that chaoses are found in, and the mechanisms by which the fractures formed. Hypotheses range from mechanisms involving water, e.g., ice melt, overturn of sediment-covered paleolakes, or submarine landslides, to purely magmatic processes, such as caldera formation, to exotic endmembers including clathrate decomposition. These interpretations of martian chaos are largely based on photogeological mapping of individual chaoses, and have mostly neglected analysis of the chaos fracture network and its relationships with the chaos basin. Here, we show, based on analysis of 35,964 fracture blocks across 18 different chaoses and 6 terrestrial analogs, and supported by novel volumetric measurements of chaos terrain deposits and intervening void spaces, that the geometry of martian chaoses is best explained by depressurization and compaction of an underlying confined aquifer. Block size distributions are incompatible with magma chamber collapse analog experiments. We show that sedimentary fill in chaos basins is inhomogeneously distributed, with layers thickening towards the chaos center, as in terrestrial sedimentary basins. The relationship between fracture block thickness and area is explained by the same power law that describes fracture spacing and layer thickness in weak terrestrial sandstones. The presence of some chaoses with blocks that are higher than surrounding plains implies repressurization of some sub-chaos aquifers. Hesperian-aged water or ice may remain within ∼1–3 km of the surface beneath these landforms.
期刊介绍:
Icarus is devoted to the publication of original contributions in the field of Solar System studies. Manuscripts reporting the results of new research - observational, experimental, or theoretical - concerning the astronomy, geology, meteorology, physics, chemistry, biology, and other scientific aspects of our Solar System or extrasolar systems are welcome. The journal generally does not publish papers devoted exclusively to the Sun, the Earth, celestial mechanics, meteoritics, or astrophysics. Icarus does not publish papers that provide "improved" versions of Bode''s law, or other numerical relations, without a sound physical basis. Icarus does not publish meeting announcements or general notices. Reviews, historical papers, and manuscripts describing spacecraft instrumentation may be considered, but only with prior approval of the editor. An entire issue of the journal is occasionally devoted to a single subject, usually arising from a conference on the same topic. The language of publication is English. American or British usage is accepted, but not a mixture of these.