Silicon Based Life Silicon Based Life FormsForms

Life on EarthLife on Earth

Chemistry of life on EarthChemistry of life on Earth

-organic-organic

-Carbon based-Carbon based

-water used as solvent-water used as solvent

-from water come hydrogen bonds, -from water come hydrogen bonds, which give structural stability to large which give structural stability to large biomolecules (proteins, nucleic acids) biomolecules (proteins, nucleic acids)

-other biologically important atoms hydrogen, -other biologically important atoms hydrogen, nitrogen, oxygen, phosphorus, and sulfurnitrogen, oxygen, phosphorus, and sulfur

Basic Facts about CarbonBasic Facts about Carbon

Atomic Number = 6Atomic Number = 6

Atomic Symbol = CAtomic Symbol = C

Atomic Weight = 12Atomic Weight = 12

Melting Point = 3500 CMelting Point = 3500 C

Boiling Point = 4827 CBoiling Point = 4827 C

66thth most abundant element most abundant element in the universein the universe

http://www.chemicalelements.com/elements/c.html

Periodic TablePeriodic Table

Basic facts about SiliconBasic facts about Silicon

Atomic Number = 14Atomic Number = 14

Atomic Symbol = SiAtomic Symbol = Si

Atomic Weight = Atomic Weight = 28.2128.21

Melting Point = 1414 Melting Point = 1414 CC

Boiling Point = 3265 CBoiling Point = 3265 C

http://www.chemicalelements.com/elements/c.html

Silicon in the Solar SystemSilicon in the Solar System

-Present in the Sun and Stars-Present in the Sun and Stars

-Principal component of a class of meteorites -Principal component of a class of meteorites known as aerolitesknown as aerolites

-group of meteorites chiefly containing -group of meteorites chiefly containing silicatessilicates

-Makes up 25.7% of Earth’s crust by weight-Makes up 25.7% of Earth’s crust by weight

-Second most abundant element, behind -Second most abundant element, behind oxygenoxygen

-Sand, quartz, flint, granite, clay, -Sand, quartz, flint, granite, clay,

What Silicon is used forWhat Silicon is used for

Produce electronic devicesProduce electronic devices

-exp: transistor, -exp: transistor, integrated circuits, solar integrated circuits, solar cells, computer chips…cells, computer chips…

-microelectronics-microelectronics

Great semiconductorGreat semiconductor

Used to make concrete and Used to make concrete and bricksbricks

Silicon ImplantsSilicon Implants

Principle ingredient of glassPrinciple ingredient of glass

Why Silicon?Why Silicon?

Similar chemical properties to CarbonSimilar chemical properties to Carbon

-Same number of electrons in the outer -Same number of electrons in the outer shellshell

-Four bonding sites-Four bonding sites

-can form complex molecules-can form complex molecules

-Both can form longs chains or polymers-Both can form longs chains or polymers

Most likely element as a alternative to Most likely element as a alternative to carboncarbon

History History 1891 Julius Scheiner1891 Julius Scheiner

-Astrophysicist at the University of Potsdam -Astrophysicist at the University of Potsdam -First to theorize about possibility of life based on silicon-First to theorize about possibility of life based on silicon-Thought Mercury, Venus, and Mars must contain life-Thought Mercury, Venus, and Mars must contain life-Jupiter, Saturn, and Uranus might contain life-Jupiter, Saturn, and Uranus might contain life

1983 James Emerson Reynolds 1983 James Emerson Reynolds -pointed out that the heat stability of silicon compounds might allow life to -pointed out that the heat stability of silicon compounds might allow life to exist at very high temperatures exist at very high temperatures

1929 John Haldane1929 John Haldane-suggested that life might be found deep inside a planet based on partly -suggested that life might be found deep inside a planet based on partly molten silicatemolten silicate

-silicate = type of rock that consists of silicon and oxygen-silicate = type of rock that consists of silicon and oxygen-Forms most of any terrestrial planet’s crust-Forms most of any terrestrial planet’s crust

- the oxidation of iron perhaps providing it with energy.- the oxidation of iron perhaps providing it with energy.

http://www.daviddarling.info/encyclopedia/H/Haldane.html

ExampleExample

Horta Horta

-Star Trek-Star Trek

-can move -can move through rock through rock as easily as as easily as humans humans move move through airthrough air

-lay eggs-lay eggs

ExampleExample

““Aliens” Aliens”

ExampleExample

““Lithovore”Lithovore”

-resemble a crystal -resemble a crystal robotic insectrobotic insect

-consume crystalline -consume crystalline vegetationvegetation

-live under very dense -live under very dense and thick atmosphereand thick atmosphere

-life based on electric -life based on electric energy generated by energy generated by an internal reactor an internal reactor

-lives underground-lives underground http://brattahlid.tripod.com/sw3-82web.htm

ExampleExample

Artificial IntelligenceArtificial Intelligence

RobotsRobots

-can process -can process abstract thoughts abstract thoughts and ideasand ideas

Are they alive??Are they alive??

Obstacles Facing Silicon Based Obstacles Facing Silicon Based LifeLife

Silicon is unstable or very reactive in many conformationsSilicon is unstable or very reactive in many conformations-aromatic rings, long chains, multi-ring chains-aromatic rings, long chains, multi-ring chains

Large silicon molecules has never occurred in natureLarge silicon molecules has never occurred in nature-Largest silicon molecules found only consist of 6 silicon atoms-Largest silicon molecules found only consist of 6 silicon atoms-will not be able to form large molecules such as proteins-will not be able to form large molecules such as proteins

-enzymes are a form of proteins, without enzymes, the -enzymes are a form of proteins, without enzymes, the chemical reactions will occur very slowlychemical reactions will occur very slowly

Silicon lacks chiralitySilicon lacks chirality-left and right handed conformation-left and right handed conformation-life as we know it utilizes only the right-hand sugars and the left-hand -life as we know it utilizes only the right-hand sugars and the left-hand amino acids amino acids -biochemical reactions for life are very specific -biochemical reactions for life are very specific

-”for many large biomolecules are so precise that a single -”for many large biomolecules are so precise that a single conformational change (right to left) around one carbon atom would conformational change (right to left) around one carbon atom would block the reaction” block the reaction”

-Bob Hazen (NASA Astrobiology -Bob Hazen (NASA Astrobiology Institute)Institute)-limits the number of different reactions available -limits the number of different reactions available

Obstacles Facing Silicon Based Obstacles Facing Silicon Based LifeLife

Silicon combines well with other atomsSilicon combines well with other atoms-its electronegativity is much less than carbon-its electronegativity is much less than carbon-longer bond length-longer bond length-bonds easier to break-bonds easier to break

When reacted with oxygen, silicon forms a solidWhen reacted with oxygen, silicon forms a solid-carbon dioxide-carbon dioxide-silicon dioxide is a solid (sand)-silicon dioxide is a solid (sand)-silicon has a strong affinity for oxygen, so its hard -silicon has a strong affinity for oxygen, so its hard to stop the oxidation of siliconto stop the oxidation of silicon-needs a way to get rid of the enormous amount of -needs a way to get rid of the enormous amount of solid wastesolid waste

Much less abundant in the universe than carbonMuch less abundant in the universe than carbon

Requirements for Silicon based Requirements for Silicon based LifeLife

1)A method of converting a simple silicon 1)A method of converting a simple silicon compound into a more complex and compound into a more complex and stable one using an energy source, stable one using an energy source, heat, electricity, light, sound? heat, electricity, light, sound?

2)The existence of complex silicon 2)The existence of complex silicon compounds that can serve as energy compounds that can serve as energy sources and catalysts for silicon sources and catalysts for silicon metabolismmetabolism

3)Existence of a suitable solvent 3)Existence of a suitable solvent

Areas Where Silicon Based Life Areas Where Silicon Based Life is Possibleis Possible

Oxygen Free Environment Oxygen Free Environment

Extremely hot Extremely hot environmentenvironment

Very high pressureVery high pressure

““Earth’s Core”??Earth’s Core”??

-could explain the -could explain the formation of deeply formation of deeply buried oil, gas and buried oil, gas and mineral deposits mineral deposits

-lived in ancient times ??-lived in ancient times ??http://www.thetech.org/exhibits_events/online/quakes/inside/images/corecore.gif