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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.
o - no conclusive evidence that extraterrestrials life has been found.
o - 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.
o - life is only known to exist on Earth.
o - life on Earth probably began 3.8 billion years ago.
o - first life form – probably bacteria that lived in very hot water around underwater volcanoes.
o - 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.
o - basic organic chemicals – amino acids have been detached in nebulae and meteorites.
o - huge lightning flashes may have caused big organic molecules to form on the earth when it was young.
o - 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.
o - 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.
o - 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.
o - due to these factors
– Titan is called the most Earth-like celestial object in the Solar System.
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