The sample comes from a hole about 2.5 inches deep drilled on Feb. 8 in a flat plate of sedimentary bedrock that the space agency managers have named "John Klein" in memory of a Mars Science Laboratory deputy project manager who died in 2011.

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Weighing 140kg, with hands like buckets and a face as flat as a plate, he waded into the marquee as if against a strong current of water and assumed a position in the corner.

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Because the plate is flat, it can be made of plastic and folded up for launch.

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No machine can make the plate as flat as it needs to be.

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Overall it has undecorated flat surfaces with a plate of glass on the front all the way out to a very thin rim and a blank back.

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Unlike on Earth, however, Mars has no plate tectonics, so the Martian layers are flat and not disrupted as they would be on Earth.

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