Will we need to tread lightly, in deference to the locals, when finally do make it to Mars? Pat Rawlings/SAIC/NASA hide caption

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On its way to Jupiter, the Galileo spacecraft looked back and captured this remarkable view of Earth and the moon. The image was taken from a distance of about 3.9 million miles. NASA hide caption

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An artist's impression of a gamma-ray burst, a powerful jet of energy lasting from less than a second to several minutes. The most powerful events in the universe, they are thought to be mostly associated with the explosion of stars that collapse into black holes. A. Roquette/ESO hide caption

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Venus on the eastern limb of the Sun captured by TRACE satellite. NASA hide caption

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The Venus Transit: Who Cares?

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