Lively debate.In "Martian Invasion" (SN: 11/8/03, p. 298), the white cliffs of Dover This article is about the geographical feature. For other uses, see Cliffs of Dover (disambiguation). The white cliffs of Dover, are cliffs which form part of the British coastline facing the Strait of Dover and France. are offered as a "notable example" of the precipitated carbonate deposits some have expected to find had Mars been wet and warm in the past. The Dover chalks are an unfortunate choice for comparison because they're composed primarily of the calcitic cal·cite n. A common crystalline form of natural calcium carbonate, CaCO3, that is the basic constituent of limestone, marble, and chalk. Also called calcspar. remains of microscopic marine phytoplankton phytoplankton Flora of freely floating, often minute organisms that drift with water currents. Like land vegetation, phytoplankton uses carbon dioxide, releases oxygen, and converts minerals to a form animals can use. . As most carbonate sediments on Earth are the result of direct or indirect biogenic biogenic /bi·o·gen·ic/ (-jen´ik) having origins in biological processes. biogenic having the property of originating in a biological process. activity, extensive examples of inorganically precipitated carbonate sediments will be hard to find. K.M. TOWE, TENNILLE, GA. |
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