Water FYOS 1001 Lecture 3

Presentation Topics Nuclearsynthesis (Big Bang, Stellar, and Supernova) Nuclearsynthesis (Big Bang, Stellar, and Supernova) Habitability of Planets Habitability of Planets Unique characteristics of Water Unique characteristics of Water

Is Water (H 2 O) the only choice of fluid for life in the Universe?

Need for good solvent in life Solvent = “the matrix of life” = dissolve other chemical compounds = carrying molecules to/from cells In any chemical life form, an efficient carrier of molecules is necessary. Among solid, liquid, gas solvents, liquid ones may be the most efficient. If so, what are possible solvents for life in the universe?

Good Solvents Requirements for a good solvent: Requirements for a good solvent: 1.A solvent must be abundant! 2.Remain liquid for a wide range of Temp! 3.Dissolve a wide variety of chemical compounds! Solvent T range for liquid Total range of T water0 to 100 C100 C ammonia-78 to -33 C45 C methyl alcohol-94 to +65 C159 C methane-182 to -164 C18 C ethane-183 to -89 C94 C At low temperature, chemical reactions are slower hence slower metabolism. H 2 O NH 3 CH 3 OH CH 4 C 2 H 6

Unique characteristics of Water Heat capacity and heat of vaporization  help to regulate temperature of life. Heat capacity and heat of vaporization  help to regulate temperature of life. Surface tension : tendency of liquid to form a droplet! Water has the highest surface tension among all known liquids.  Before cells evolved, surface tension would force some compounds together and would preserve the boundaries between inside/outside. Surface tension : tendency of liquid to form a droplet! Water has the highest surface tension among all known liquids.  Before cells evolved, surface tension would force some compounds together and would preserve the boundaries between inside/outside. Unique properties of Water: larger volume when frozen! Unique properties of Water: larger volume when frozen!  Bursting pipes in winter by frozen water  Frozen ponds only on the surface! Non-water based life forms do not expand upon freezing Non-water based life forms do not expand upon freezing  space travel in hibernation!  space travel in hibernation! WaterAmmonia M. Alcohol Heat Capacity Heat of Vapor

H 2 O good choice for Life Liquid Water as the best solvent for life Liquid Water as the best solvent for life 1.A wider, higher range of temperature for being liquid 2.Solid water floats over liquid water 3.Polar molecule  dissolve certain types (polar) of molecules only : cell membrane 4.Water is the most common liquid (H is the most abundant element and Oxygen is the 3 rd most common element in the Universe) 5.Heat capacity and Heat of Vaporization  regulate temperature 6.Highest surface tension

Environmental Requirements for Life 1.Must have a source of molecules 2.Must have a source of energy 3.Must have a liquid medium Any worlds meet the #3 requirement, likely meet the first two requirements also.  Why? Conservatively… A habitable world = only if it has a liquid water!

Habitability of Planets Goldilocks planets

Choice of the highest efficiency Carbon + water may be the most efficient basis of life in the Universe, but it is not the exclusive choice! Carbon + water may be the most efficient basis of life in the Universe, but it is not the exclusive choice! Less efficient bases can be used… Less efficient bases can be used… Information Storage as an example: o In English : 26 capital, 26 small letters, plus few punctuation marks (~60 “symbols”) o In computer: o In Korean : 26 모음, 26 자음, 몇가지 부호 ( 약 60 개 심볼 ) Cannot be convinced (or refuted) purely based on reasoning and analogy. Cannot be convinced (or refuted) purely based on reasoning and analogy.  A discovery of non- carbon based alien life form quickly solves the issue.  Or a series of discoveries of alien life forms that are all carbon+water…

C and H 2 O for alien life!

Report on “Carbon-Water” alien life forms in the Universe is due by this Sunday midnight!

Relative abundance of chemical elements in the Universe Cosmic Abundance Cosmic Abundance How? How? via Nuclearsynthesis

Superiority of C! Infinite number of combinations with H! Infinite number of combinations with H! C-C, C-H, and C-O bond strengths are ~same. C-C, C-H, and C-O bond strengths are ~same. Carbon is the best base element to make complex structures! Carbon is the best base element to make complex structures! Although life based on silicon may be possible, it will be extremely uncommon at best! Life based on carbon seems favored as the dominant kind of life in the Universe! Si has four “bonds” similar to Carbon. Si has four “bonds” similar to Carbon.

Origin of the Elements After Big Bang, lightest elements (H, He, Li, Be) were created, but only for a limited time period (3 to 20 minutes). 92% H + 8% He and almost no other elements.

Cosmic abundance Later stages of Nuclear fusions in Stars Later stages of Nuclear fusions in Stars Not much Li (H+He), Be, B (Be+H or He+Li)… Not much Li (H+He), Be, B (Be+H or He+Li)…