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  1. Planetary Science

    Exploring the Red Planet

    Searching for signs of subsurface water on the Red Planet and analyzing the elemental and mineral composition of surface rock, NASA's Mars Odyssey spacecraft begins its main mapping mission next month and may shed light on several enduring puzzles about the planet.

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  2. 18986

    If the stones in this article simply were used for grinding ocher to make powder, would not the grinder rough up the surface to make it a better grindstone? The marks may be nothing more than primitive knurls. Rather than art, this looks like a tool to me, not different in principle from flaked flint. […]

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  3. Anthropology

    Stone Age signs of complexity

    Ancient engravings found in South Africa support the theory that humans began to think and behave in symbolic ways a surprisingly long time ago.