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首页> 外文会议>Conference on Instruments, Methods, and Missions for Astrobiology V, Aug 22-23, 2002, Waikoloa, Hawaii, USA >Dissolution cavities in Upper Ordovician sandstones from Lake Ontario: Analogs to vesiculated rocks on Mars?
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Dissolution cavities in Upper Ordovician sandstones from Lake Ontario: Analogs to vesiculated rocks on Mars?

机译：安大略湖上奥陶纪砂岩中的溶蚀空洞：类似于火星上的孔状岩石吗？

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摘要

Fossiliferous sandstones of the Upper Ordovician (Lorraine Group) found along the Erie-Ontario Lowlands represent near-shore marine invertebrate communities which dominated the warm shallow sea that existed in this region 450 my ago. Subsequent glacial scouring and breakup of this ancient seabed during the Pleistocene resulted in its being buried under glacial sediments and soil. Then over a period of thousands of years, mild carbonic acid from rainwater mixed with humic acids from soil percolated through the sandstones and dissolved the entombed fossils leaving only dissolution cavities. This same process is how caves and karst features are formed. Rocks imaged by NASA'sViking 2 lander in 1976 revealed ubiquitous "vesicles" that to this day remain enigmatic because the mineralogy of Martian rocks has not been adequately analyzed to date. Neither a sedimentary nor a volcanic origin for the rocks has been firmly established. Furthermore, proposed theories on the evolution of the Utopia Basin near the Viking 2 landing site include an ancient shallow ocean and glacial scouring. If Mars did indeed have an ocean at one point in its history, then the question must be asked "Did Martian lakes and oceans also have time enough for the development of life and ultimately to the multicellular stage that may have left traces of their existence as dissolution cavities? In this report, attention is drawn to the morphological similarities of biogenic dissolution cavities in terrestrial sandstones and in the near-field rocks at the Viking 2 landing site on Mars. The Beagle 2 astrobiology lander, part of the ESA's Mars Express mission in 2003, will once again land in the northern plains of Mars not far from the shoreline of the proposed northern ocean basin. A comparison of the rocks from the Beagle 2 landing site to those at Viking 2 may shed further light on whether they are sedimentary or volcanic in origin, and, of greatest interest, whether the vesicles in the Martian rocks constitute analogs to the biologically formed dissolution cavities in the rocks of the Upper Ordovician on Lake Ontario.
机译：在伊利-安大略低地上发现的上奥陶纪的化石砂岩（洛林群）代表了近岸的海洋无脊椎动物群落，这些群落主导了450年前我在该地区存在的温暖的浅海。随后在更新世期间，这个古老海床的冰川冲刷和破裂导致其被埋在冰川沉积物和土壤之下。然后，在数千年的时间里，雨水中的轻度碳酸与土壤中的腐殖酸混合，渗透到砂岩中，溶解了被包埋的化石，仅留下了溶蚀腔。形成洞穴和喀斯特地貌的过程与此相同。 1976年，由NASA的《维京2号》着陆器成像的岩石显示出无处不在的“囊泡”，由于至今尚未对火星岩石的矿物学进行充分的分析，因此至今仍是谜团。尚未确定岩石的沉积或火山成因。此外，关于维京2号登陆点附近的乌托邦盆地演化的提议理论包括古老的浅海和冰川冲刷。如果火星确实在其历史的某一时刻确实拥有海洋，那么必须提出以下问题：“火星人的湖泊和海洋是否也有足够的时间来发展生命，并最终进入多细胞阶段，可能留下其生存痕迹。溶蚀腔？在此报告中，人们关注了火星上的维京2号着陆点的陆地砂岩和近场岩石中生物溶蚀腔的形态相似性。在2003年，它将再次降落在距离拟议的北洋盆地海岸线不远的火星北部平原，将比格2号登陆点的岩石与维京2号的岩石进行比较可能会进一步阐明它们是否属于沉积岩。或火山成因，最受关注的是火星岩石中的囊泡是否类似于上奥德岩石中生物形成的溶蚀腔类似物安大略湖上的火山岩。

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