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In page Robert Zubrin:

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Zubrin is an advocate of a moderately anthropocentric position in the ethics of terraforming. Discussions of the ethics of terraforming often[citation needed] make reference to a series of public debates Zubrin has held with his friend Christopher McKay, who advocates a moderately biocentric position on the ethics of terraforming. For example, a written account of some of these debates is available in On to Mars: Colonizing a New World, as a joint article, "Do indigenous Martian bacteria have precedence over human exploration?" (pp. 177–182).