Word: sagan
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...Astronomer Carl Sagan...
...detecting any signs of life on Mars from a distance of thousands of miles, Sagan sifted through pictures of the earth taken by weather satellites and discovered that only one shot in a thousand showed evidence of man's presence. He presented his conclusions in a provocative paper that in effect asked: Is there life on earth? Later, Sagan puckishly noted that Martians visiting the earth might believe that automobiles were the dominant form of terrestrial life; the environment is altered to fit their needs and they act much like living beings by moving, eating and excreting...
Exobiologists have suggested a number of scenarios for the survival of Martian life. Sagan, for instance, theorizes that Mars may now be experiencing an ice age. As he explains it, the planet's northern hemisphere does not now receive the maximum possible dose of solar radiation because the Martian north pole is tilted toward the sun only when the planet is farthest from it. Yet in about 10,000 to 12,000 years, because of the slow precession of Mars (a wobbling of the planet as it rotates through space), the north pole will be tilted so that it receives...
That chauvinism is displayed time and again, say exobiologists, by those who cannot conceive the possibility of life without water (which Sagan calls "liquid-water chauvinism"), without oxygen ("oxygen chauvinism") or in the presence of intense ultraviolet radiation ("ultraviolet chauvinism"). Yet life can indeed develop under conditions radically different from those on earth. It did, for example, evolve during untold eons on earth when there was no oxygen in the atmosphere. To those primitive forms of life, in fact, oxygen would have been a poisonous gas. Thus instead of requiring oxygen, Martian organisms, like some terrestrial bacteria, might thrive...
...their bleak planet. If Martian creatures found intense ultraviolet radiation unbearable, Sagan speculates, they may have developed tough silicate shells that would protect them from it. The reason that Mars does not reflect back much ultraviolet radiation, he says whimsically, may be that all those turtle-like creatures are absorbing...