Lecture 8

Lecture 8 - ing for Life in Our Solar S Introduction...

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hing for Life in Our Solar S
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Introduction Key Point Where (other than Earth) in the solar  system might we expect to find the  conditions needed for life?  We expect these conditions to be:  Availability of basic chemical elements  needed for life (C,H,O,N and other trace  metals) Access to an energy source (the sun,  chemical energy, heat from some source  etc.) Presence of a liquid (probably water) to  catalyse chemistry and allow molecules  mobility For our Solar System at least – we are  looking for microbes. Confident that there is no other advanced  civilization in our Solar System.
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There’s no place like home! Would need self-contained habitats built or to terraform the planet for us to survive  elsewhere. Habitability = where some kind of life might survive, not necessarily humans! To identify potentially habitable worlds in our Solar System, must specify the range  of environments we consider acceptable to life. No world other than Earth has:  an atmosphere that we could breathe, an abundance of surface water that we  could drink, a combination of surface temperature and  pressure which we can survive without a  suit, an atmosphere that could offer any  protection from UV radiation.
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The Building Blocks of Life Most obvious requirement for life: set of chemical  elements with which to make the components of  cells. Life on Earth uses 25 of 92 naturally occurring  elements -> only O, C, H, N = 96% of the mass of living  organisms. First requirement for life = most/all elements used  by life. Met by almost any world – all  chemical elements (not H  and He) produced by stars,  and found everywhere. rd th th
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The Building Blocks of Life The nature of Solar System formation: Planets were built when solid particles  condensed  from gas in the solar nebula ->  these particles accreted into planetesimals -> then made planets, moons, asteroids  and comets. Condensation  – affects only the heavier elements (or H compounds containing  heavy elements) – H and He remain as gases. Expect the resultant worlds to contain the elements needed for life. Carbon based life?  Any element chosen would still be created by stars and found  everywhere.
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The Building Blocks of Life Remember : Earth’s organic building blocks came from a combination of three  sources: chemical reactions in the atmosphere, space, deep-sea hydrothermal  vents. Atmosphere and deep-sea = needs a planet with atmospheres or oceans.
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Lecture 8 - ing for Life in Our Solar S Introduction...

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