新加坡六合彩开奖直播

Polygonal features of diameter 20B200 m, recently identified at mid high latitudes of Mars in high resolution (1.5 13 m/pixel) digital images, are visually similar to ice wedge patterns that form by seasonal cooling of ice rich permafrost in Earth's arctic regions. Other hypotheses for Mars networks include desiccation, structural bending, or deep climatic cooling. Here I investigate hypotheses by applying quantitative comparisons of Mars= networks from Utopia Planitia (43.5 N, 269.3 W) with terrestrial ice wedge patterns located at the mouth of the Sagavanirktok River, near Prudhoe Bay, Alaska (701N,1471W), as well as with experimental desiccation fracture patterns. Statistical metrics include intersection types, polygon size, relative orientation between neighbouring fracture segments, and degree of orderliness. I find that Utopia Planitia networks a) are qualitatively similar to terrestrial ice wedge networks with respect to intersection types and degree of orderliness, but have larger spacing; b) are distinctively different from fracture patterns that form by a single fracture event, such as desiccation patterns in mud; and c) display strong north northeast orientation over large regions, approximately parallel to the regional topographic slope into the Utopia basin. I conclude that Mars networks formed by recent and multiple fracture events, likely caused by seasonal cooling similar to terrestrial permafrost patterns, and not by other proposed mechanisms.

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Pages: 200
Supervisos: Lawrence Plug