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In reply to the discussion: Does the Big Bang breakthrough offer proof of God? [View all]RainDog
(28,784 posts)But it's my understanding that the reason Mars does not contain complex life forms (maybe there's bacteria there - or unicellular organisms like those that made up the bulk of life during the entire course of life on earth - 4/5ths of the time that life has existed on earth, over billions of years, that life was made up of simple unicellular organisms. It was only about 500 million or so years ago that multicellular organisms appeared on earth.
The reason is that Mars is a lower mass planet than earth. Such planets cannot sustain gravitational pull to maintain an atmosphere. Basic chemicals can be lost because of this insufficient gravity, and thus do not allow the creation of a thick atmosphere with the biochemicals that flourish within such thick atmospheres (The atmosphere of Mars is very thin compared to the earth.) The size of the planet also determines temperature (as well as its location in relation to the sun) and temperature is another feature that works symbiotically with mass and gravitational pull to cook up a carbon-based life stew. Smaller planets also lack the energy from their cores to sustain geologic activity that gives rise to carbon dioxide. Because of this lack of geologic activity, Mars does not generate a magnetic field to help contain an atmosphere conducive to producing life as we understand it from hydrogen, carbon, oxygen and nitrogen.
But some scientists think ammonia, rather than our atmosphere, might be the basis for silicon life forms, so there may be life in other places that we have not yet seen. There are also other possible habitable planets in other galaxies.