Life

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No direct evidence (yet) that there is life
on other planets, moons, or in interstellar space.

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Life
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  • existence of life beyond Earth is a topic of ongoing scientific investigation.
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  • no conclusive evidence that extraterrestrials life has been found.
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  • all planets, including Earth are the product of their unique history and environment, so it’s possible alien life could exist under very different conditions than what we know ~ the role of science in this is to constrain the imagination, and consider realistic possibilities for different pathways for life.
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  • life is only known to exist on Earth.
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  • life on Earth probably began 3.8 billion years ago.
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  • first life form – probably bacteria that lived in very hot water around underwater volcanoes.
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  • most scientists believe that life’s basic chemicals formed on Earth – others think that they came from space, maybe on comets.

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Life


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Origins of life
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  • most scientists believe that life’s basic chemicals formed on Earth – others think that they came from space, maybe on comets.
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  • basic organic chemicals – amino acids have been detached in nebulae and meteorites.
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  • huge lightning flashes may have caused big organic molecules to form on the earth when it was young.
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  • Earth is suitable for life because of
    – its gas atmosphere (oxygens)
    – surface water
    – moderately warm temperatures.

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The atmosphere of Titan
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  • atmosphere of Titan mainly nitrogen and methane;
    – minor components lead to the formation of hydrocarbon clouds
    – heavy organonitrogen haze.
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  • climate
    – including wind and rain
    – creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas (probably of liquid methane and ethane) and deltas.
    – dominated by seasonal weather patterns as on Earth.
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  • with its liquids (both surface and subsurface) and robust nitrogen atmosphere;
    – Titan’s methane cycle nearly resembles Earth’s water cycle.
    – albeit at a much lower temperature of about −179 °C / −290 °F.
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  • due to these factors
    – Titan is called the most Earth-like celestial object in the Solar System.


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