Astronomy 2021A/B Lecture Notes - Lecture 6: Sample-Return Mission, Robotic Spacecraft, Extremophile
1 Jun 2017
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Document Summary
Life on earth uses about 25 of the 92 naturally occurring chemical elements, although just four of these elements (oxygen, carbon, hydrogen, and nitrogen) make up about 96% of the mass of living organisms. Essentially all chemical elements besides hydrogen and helium were produced by stars. The elements oxygen, carbon, and nitrogen are arguable the most crucial elements for life. Every star system we"d studies has at lease some amount of all the elements used by life. No matter what kind of life we are looking for, we are likely to find the necessary elements on almost every planet, moon, asteroid, and comet in the universe. Earth"s organic molecules likely came from some combination of three sources: chemical reactions in the atmosphere, chemical reactions near deep-sea vents in the oceans, molecules brought to earth from space. Interplanetary dust may have contained organic molecules that rained down on young worlds.
