Asteroids, in some sense, are like flying gold mines in outer space. For example, in July 2015, one came within a million miles of Earth, or about four times the distance from the Earth to the moon. It was about nine hundred meters (or about three thousand feet) across and was estimated to contain ninety million tons of platinum in its core, worth $5.4 trillion. Planetary Resources estimates that the platinum within a mere thirty-meter asteroid could be worth $25 to $50 billion. The company has gone so far as to make a list of small nearby asteroids that are ripe for the taking. If any one of
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