Colonization of Titan Zubrin has pointed out that Titan possesses an abundance of all the elements necessary to support life, saying "In certain ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization." The atmosphere contains plentiful nitrogen and methane, and strong evidence indicates that liquid methane exists on the surface. Evidence also indicates the presence of liquid water and ammonia under the surface, which are delivered to the surface by volcanic activity. Water can be used to generate breathable oxygen and nitrogen is ideal to add buffer gas partial pressure to breathable air (it forms about 78%
Atmosphere of Earth development of animals. Today's atmosphere contains 21% oxygen, which is great enough for this rapid development of animals. "Air pollution" is the introduction into the atmosphere of chemicals, particulate matter or biological materials that cause harm or discomfort to organisms. Stratospheric ozone depletion is caused by air pollution, chiefly from chlorofluorocarbons and other ozone-depleting substances. The scientific consensus is that the anthropogenic greenhouse gases currently accumulating in the atmosphere are the main cause of global warming. On October 19, 2015 NASA started a website containing daily images of the full sunlit side of Earth on http://epic.gsfc.nasa.gov/. The images are taken