The lake bed is formed of a fine-grained mudstone, rich in clay.

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Other catalogue items, such as the tyrannosaur tooth, openly referred to the Nemegt Formation, a fossil-rich expanse of sandstone and mudstone in the Mongolian Gobi.

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In the grit of fine-grained mudstone, the scientists identified sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon some of the key chemical ingredients for conditions suitable for life.

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Curiosity is due to turn its drill again in this mudstone for further analysis before climbing out of Yellowknife Bay and heading for the crater's big central mountain, Aeolis Mons (Mount Sharp).

BBC: Curiosity Mars rover to investigate classic rock type

Just before conjunction, it drilled into a mudstone in a rock unit referred to as Sheepbed and found further compelling evidence for a watery past in Gale - sediments that possibly once formed a lakebed.

BBC: Curiosity Mars rover to investigate classic rock type

After Emily hit upon the fossil with a spade, her father and palaeontologist Dr Neville Hollingworth helped her dig out the block of mudstone the 162.8 million-year-old object, which had spikes to ward off predators, was encased in.

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