Astromaterials Research and Exploration Science Directorate, NASA-Johnson Space Center, Houston, Texas 77058, USA.
Astrobiology. 2012 Jun;12(6):601-15. doi: 10.1089/ast.2011.0803. Epub 2012 Jun 25.
This paper presents the hypothesis that the well-known giant polygons and bright mounds of the martian lowlands may be related to a common process-a process of fluid expulsion that results from burial of fine-grained sediments beneath a body of water. Specifically, we hypothesize that giant polygons and mounds in Chryse and Acidalia Planitiae are analogous to kilometer-scale polygons and mud volcanoes in terrestrial, marine basins and that the co-occurrence of masses of these features in Chryse and Acidalia may be the signature of sedimentary processes in an ancient martian ocean. We base this hypothesis on recent data from both Earth and Mars. On Earth, 3-D seismic data illustrate kilometer-scale polygons that may be analogous to the giant polygons on Mars. The terrestrial polygons form in fine-grained sediments that have been deposited and buried in passive-margin, marine settings. These polygons are thought to result from compaction/dewatering, and they are commonly associated with fluid expulsion features, such as mud volcanoes. On Mars, in Chryse and Acidalia Planitiae, orbital data demonstrate that giant polygons and mounds have overlapping spatial distributions. There, each set of features occurs within a geological setting that is seemingly analogous to that of the terrestrial, kilometer-scale polygons (broad basin of deposition, predicted fine-grained sediments, and lack of significant horizontal stress). Regionally, the martian polygons and mounds both show a correlation to elevation, as if their formation were related to past water levels. Although these observations are based on older data with incomplete coverage, a similar correlation to elevation has been established in one local area studied in detail with newer higher-resolution data. Further mapping with the latest data sets should more clearly elucidate the relationship(s) of the polygons and mounds to elevation over the entire Chryse-Acidalia region and thereby provide more insight into this hypothesis.
本文提出了一个假设，即火星低地中广为人知的巨型多边形和明亮土丘可能与一个共同的过程有关——一种由细粒沉积物在水体下掩埋而导致的流体排出过程。具体来说，我们假设 Chryse 和 Acidalia 平原的巨型多边形和土丘类似于地球、海洋盆地中公里级规模的多边形和泥火山，而 Chryse 和 Acidalia 中这些特征的大量共存可能是火星古代海洋中沉积过程的特征。我们的假设基于地球和火星的最新数据。在地球上，三维地震数据说明了公里级规模的多边形，它们可能与火星上的巨型多边形类似。地球的多边形形成于细粒沉积物中，这些沉积物已被沉积和埋藏在被动边缘、海洋环境中。这些多边形被认为是压实/脱水的结果，它们通常与流体排出特征（如泥火山）有关。在火星上，Chryse 和 Acidalia 平原的轨道数据表明，巨型多边形和土丘具有重叠的空间分布。在那里，每组特征都出现在类似于地球公里级多边形的地质环境中（宽阔的沉积盆地、预测的细粒沉积物和缺乏显著的水平应力）。在区域上，火星上的多边形和土丘都与海拔相关，就好像它们的形成与过去的水位有关。尽管这些观测结果是基于覆盖不完全的旧数据得出的，但在一个用更新的高分辨率数据进行了详细研究的局部区域已经建立了类似的与海拔的相关性。用最新数据集进行进一步的测绘应该可以更清楚地阐明整个 Chryse-Acidalia 地区多边形和土丘与海拔的关系，并为这一假设提供更多的见解。
