Last updated on Dec. 23, 2015
Mars Bagnold Dune No. 2 contains numerous ooids (photo below). Ooids are usually composed of calcium carbonate, which is the main component of shells of marine organisms. The nuclei of ooids can be shell fragments of marine organisms (https://en.wikipedia.org/wiki/Ooid#Formation ).
Added on Dec. 9, 2015: More Martian Ooids Marked in These Two Figures:
The above microscopic image was taken by NASA’s Mars rover Curiosity on Dec. 5, 2015 (Sol 1184) near Bagnold Dune #2, Gale Crater, Mars. Four red lines go to whitish ooids on the sand dune. They are all smaller than 2 mm across. Image source: mars.nasa.gov/msl/multimedia/raw/?rawid=1184MH00054800104…
The above microscopic image was taken by NASA’s Mars rover Curiosity on Dec. 5, 2015 (Sol 1184) near Bagnold Dune #2, Gale Crater, Mars. Six red lines go to ooids on the sand dune. They are all smaller than 2 mm across. Image source:mars.nasa.gov/msl/multimedia/raw/?rawid=1184MH00016300004…
Highest resolutions for the above two figures are displayed at
Added on Dec. 10, 2015: Tons of Carbonate in Gale Crater
On Earth, at the Bahamas alone, there are billions of tons of ooid sands (note 1). The following photo shows some of the carbonate in Gale Crater:
Photo shows a part of Gale Crater, Mars. Mars rover Curiosity landed at upper right. Mount Sharp is at lower right. Red and yellow lines at center mark High Dune and Namib Dune. Green lines and green rectangles mark dunes similar to High Dune and Namib Dune. Enormous is the dune at bottom left. Image source: see reply 278 inwww.marsroverblog.com/discuss-213447-active-marspage14.html
Added on Dec. 11, 2015: Most Ooids Originated from Organisms.
Ooids are usually comprised of calcium carbonate (note 1). Carbonate sediments are comprised of minerals deriving from organisms (note 2). So, most ooids originated from organisms.
Note 2: “Modern carbonate sediments are comprised of three principal minerals: aragonite, calcite (CaCO3) and dolomite (CaMg (CO3)2). The mineral type is determined by the organism from which the grains are derived.” (Quoted from the first paragraph in http://geology.uprm.edu/Morelock/carb.htm)
Added on Dec. 12, 2015: Correct Identification of Ooids
Viewers can compare ooids there with those on Mars.
Added on Dec. 14, 2015: Ooids Differ from Other Spheres in Sizes.
Ooids are mostly no larger than 2 mm in diameter. However, “On Mars, most of the hematite rocks (“blueberries”) are about 0.16 inches (4 millimeters) in diameter, and no larger than 0.24 inches (6.2 millimeters). By contrast, Earth spherules exhibit a large range of sizes, not limited to only a quarter of an inch.” Quoted from the ninth paragraph inhttp://news.nationalgeographic.com/news/2014/02/140224-mars-blueberries-water-meteorite-space-science/
Added on Dec. 15, 2015: Environment of Ooids
“They (ooids) are usually formed in warm, supersaturated, shallow, highly agitated marine water intertidal environments, though some are formed in inland lakes.” (Quoted from second paragraph of https://en.wikipedia.org/wiki/Oolite#Composition )
“Although the most widely distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions and associated withancient lake or sea beds.” (See second paragraph of https://en.wikipedia.org/wiki/Dune)
Added on Dec. 23, 2015: Most Aragonite Was Created by Life.