Making Mars habitable.
Mars is believed to be lifeless, but it may be possible to transform it into a planet suitable for habitation by plants, and conceivably humans.  The success of such an enterprise would depend on the abundance, distribution and form of materials on the planet that could provide carbon dioxide, water and nitrogen.
McKay
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CP
Space Science Division, NASA Ames Research Center, Moffett Field, California 94035, USA.
Toon
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OB
Kasting
J F
JF
D001272:Atmosphere; D002245:Carbon Dioxide / Q000032:analysis; D002980:Climate; D005118:Extraterrestrial Environment; D017752:Greenhouse Effect; D018535:Mars; D009584:Nitrogen / Q000032:analysis; D010100:Oxygen / Q000032:analysis; D018521:Plant Physiological Phenomena; D013026:Space Flight / Q000639:trends*; D014867:Water / Q000032:analysis
D014867:Water; D002245:Carbon Dioxide; D009584:Nitrogen; D010100:Oxygen