The mystery of life itself… We each spend our own lifetimes trying to answer that question in our own way



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Origin of Life

  • In an age when most great mysteries have long since yielded to human ingenuity or stubbornness, one all-important mystery remains

  • The mystery of life itself…

  • We each spend our own lifetimes trying to answer that question in our own way

  • What is our life all about, where are we going, what comes after life, how we should behave in response to the answers we discover…

  • But there is one part of this cosmic problem that we are finally starting to understand

  • How did life on Earth begin…

  • How has life changed over the billions of years our planet has survived?

  • The long and complex history of life on Earth may never be completely told

  • But we know enough to chart its tenacious course through eons of geologic time

  • What was the world like before living organisms changed it forever?

  • Prebiotic evolution - evolution of complex networks of organic compounds before the origin of life

  • Evolution of self-replicating networks of chemical reactions, start of living systems

  • 3.5 - 4 billion years ago - organic compounds must have filled the water where life evolved

  • What were these first complex organic compounds like?

  • We will never know, except in theory

  • The answer was eaten up a long time ago…

  • First unicellular organisms would have feasted on these complex organic compounds

  • Where did we come from?

  • How did our planet originally form?

  • Stars and planets form from vast clouds of cosmic dust

  • Think of the magnificent spiral arms of a typical galaxy

  • Galaxies rotate around their axis, like solar systems but on a much grander scale

  • Rotation produces density waves

  • Density waves trigger the collapse of large fragments of cosmic dust clouds

  • Rotation of the spiral arms spawns tens of thousands of new suns in its wake

  • Gravitational attraction pulls the particles of the cosmic cloud together

  • As it collapses, the cloud begins to spin

  • Pressure increases in the condensing cloud of gas, generates heat

  • Forms a solar nebula or accretion disk, vast band of debris, gas, dust, rotating around the protostar

  • Heat eventually becomes great enough to ignite the protostar

  • ~ 107 degrees Kelvin required to start the process of nuclear fusion (H Bomb)

  • Same basic process forms the planets

  • The spinning cloud of ever-condensing cosmic gas (solar nebula) throws off an immense belt of matter

  • Belt of rotating matter is called an accretion disk or protoplanetary disk

  • Protoplanetary disk coalesces into planets and moons

  • Until recently, all of this was purely theoretical

  • Thanks to the Hubble Space Telescope and other modern super-scopes, we have now photographed these protoplanetary disks

  • We have discovered a wealth of similar disks, scattered throughout the small portion of the universe we have observed

  • Some of them are vastly larger than the one that gave birth to our own planet


  • Through careful observation of minute fluctuations in the light of distant suns, we have inferred the existence of numerous planetary systems in the cosmos

  • We may no longer be completely alone…


  • Two methods used to detect extrasolar planets:

  • Radial velocity method (gravitational wobble)

  • Transit method (solar dimming from rotating planets)


  • As of Feb. 2014, we’ve identified 1075 extrasolar planets!

  • Most of them are very large, Jupiter-like planets, so not likely to support life

  • First distant planets were photographed in 2008 (using infrared), circling HR8799, 130 light years away!

  • NASA launched Kepler satellite in 2009

  • Specifically designed to watch solar transits for new planets

  • Mission discovered several hundred new solar systems

  • 2013 Kepler picked up first small planet, less than the size of Mercury

  • Kepler 37 system also contains an Earth size planet


  • 2014 Kepler 186f discovered, 500 light years away

  • Earth size and in the outer edge of the Goldilocks zone

  • 2017 NASA plans to launch Transiting Exoplanet Survey Satellite (son of Kepler)


  • MIT’s Murchison Widefield Array, located in the Western Australia Outback, is another new tool in the search for intelligent life in space

  • The telescope features 512 tiles, each containing 16 antennae, for a total of 8,192 antennae!

  • Computer integration allows the separate antennae to function as if they were one single huge antenna dish = 8,192 m2

  • Trained on the 21 cm band of Hydrogen/Hydroxyl ion (H/OH), the so-called galactic “watering hole”

  • Basic idea is that water is so essential to life that all alien races, knowing that to be true, would most likely broadcast their signals in that range, where another race would most likely be listening – big assumption!

  • Though designed to study the role of hydrogen in the early evolution of the universe, the focus on the 21 cm Hydrogen band means the data can also be used to look for SETI signals

  • Deep space photographs show immense galactic clusters

  • There may be as many as 100 billion galaxies in the universe

  • Each galaxy may hold 100 billion stars

  • Surely, in all that magnificent immensity, there must be other worlds and other races

  • Brush up on your klingon verbs, just in case…

  • Where is everybody?

  • SETI and other cosmic search projects have been listening in vain for several years for signals from the stars

  • So far, nothing but static - like a really bad AM radio

  • Scanning the universe for signs of intelligent life is a big job

  • A very small needle in a very large haystack

  • We can roughly calculate the likelihood of contact by using the Drake Equation

  • N = R* fp ne fl fi fcL – multiply the probabilities

  • N = # of intelligent alien civilizations in the galaxy that could communicate with us

  • N = R* fp ne fl fi fcL

  • R* = rate of star formation

  • fp = fraction of stars with habitable planets

  •  ne = # of planets per star capable of supporting life

  • fl = fraction of planets that develop life

  • fi = fraction of planets that evolve intelligent life

  • fc = fraction of planets that develop a technology

  • L = average lifetime of a technological society

  • Range of published estimates is very high, 0.003 to 2x106

  • civilizations will destroy themselves

  • Given our history, may be unfortunately close to the truth!

  • Low end is a pessimistic one, assumes that L will be very short, because most high tech I


  • Petigura (2013) concludes from Kepler data that ne ~ 22%

  • ne = # of planets per star capable of supporting life, i.e earthlike planets in the “Goldilock’s zone”

  • Our galaxy may hold 40 billion earth-like planets

  • If this is the only planet in the cosmos that supports intelligent life, then we have a special responsibility to take very good care of it!

  • Now we have sent ships deep into uncharted space

  • We now see our world as it really is, a small ball of rock spinning through the vast stretches of empty space

  • Could other planets support life?

  • Consider our own solar system

  • Our own moon is a ball of lifeless rock, devoid of air or surface water

  • The Spirit and Opportunity probes now on the Martian surface have discovered unmistakable evidence that Mars was once bathed in liquid water

  • But Mars has become a dried husk

  • If life ever existed on Mars it is long gone

  • Curiosity probe landed August ‘12

  • May shed new light on the possibility of life on Mars

  • Don’t look to Venus for signs of life

  • Venus is consumed by a runaway greenhouse effect, with surface temperatures that would melt lead

  • Jupiter and Saturn are violent swirls of toxic gas and crushing pressure

  • Neptune, Uranus, and Pluto are frozen orbs far away from the life-giving sun

  • Of all the moons and planets in our solar system, only distant Europa, one of Jupiter’s many moons, may be home to life

  • Space scientists believe that under Europa’s shell of ice lies a sea of liquid water, which may be a cradle of life

  • NASA (2014) added Saturn’s moon Enceladus to the list

  • Evidence for a sea of liquid water under the ice, the size of Lake Superior


  • Why all the fuss about water?

  • What makes water so essential to life is its many unusual chemical properties

  • The nature of life is fundamentally shaped by water

  • Water is the essence of life

  • Living things made mainly of water

  • Water is an essential ingredient in photosynthesis

  • Chemical and physical properties of water make life possible

  • Water molecules are simple, yet strange…

  • The two hydrogen atoms bond to one end of the lone oxygen atom to make water

  • They stick to one end of the atom, creating a slightly polarized molecule

  • One end has a small positive charge, the other a small negative charge

  • This polarity causes water molecules to stick together

  • It also gives water its many interesting properties

  • Water has a high specific heat - it requires a huge amount of energy to heat water, and it gives off much energy when it cools

  • Water expands just before the freezing point

  • That’s why you never want to forget a bottle of beer in the freezer

  • Ice is lighter than water, so it floats to the top when it forms

  • That means bodies of water don’t freeze from the bottom up

  • Insulating layer of ice makes aquatic life possible in colder climates

  • Water also has a high surface tension

  • This means that when water enters a tube it tends to pull other water molecules along with it

  • Capillary action lets plants grow tall, still conduct water and nutrients to the leaves

  • Many exobiologists (study of life beyond the Earth) are convinced that life could not evolve without water

  • Carbon is another element with unusual properties that make it highly suitable for life

  • Bonds to itself very firmly, forms long chains that are the backbone of most biomolecules (C/H/O)

  • Carbon exists in both gaseous and solid states, readily dissolves in water

  • Carbon can form up to four chemical bonds

  • Oxygen has only two bonds (linear)

  • Nitrogen has only three bonds (planar)

  • Carbon has four bonds, so it can be used to form complex three dimensional molecules

  • Carbon also bonds to itself to forms cyclic rings (aromatic compounds), many complex shapes are possible

  • An equally important ingredient in the history of life is time

  • Given a billion years of random chemistry, even the most improbable events can become a reality

  • Once the Earth was formed, it took a billion years of prebiotic evolution to produce the first living organism

  • If we took a trip through time to four billion years ago, what would we find?

  • Earth was not a very pleasant place…

  • When the Earth formed from the protoplanetary disk, there was still much debris orbiting the Sun

  • Result was five hundred million years of intense meteor bombardment

  • The moon was probably formed by an immense collision between the still molten Earth and a Mars-sized chunk of debris

  • To see how violent the impacts were, look at the surface of the moon - no erosion

  • Infant Earth was covered with molten lava and boiling pools of mud and water

  • Atmosphere was turbulent and toxic mixture of carbon dioxide, methane, hydrogen sulfide - no oxygen

  • Scientists call this period of Earth’s history the Hadean - a most appropriate name

  • Life evolved in these extreme habitats

  • Most primitive microbes on Earth today are adapted to extreme heat

  • Origin of life took place relatively quickly

  • Age of the Earth ~ 4.56 billion years

  • Last major impacts ~ 4.2 bya

  • Oldest trace of photosynthesis ~ 3.8 bya

  • So life evolved roughly ~ 3.9 to 4.2 bya


Directory: ~bfleury -> historyoflife -> lectures
~bfleury -> In our last lecture, we looked at the ways that trade, travel, technology and agriculture can provide new habitats and new dispersal routes for microbes
lectures -> Dinosaurs 3 Several morphological features suggest dinosaurs relied on visual displays for communication, like modern animals
lectures -> Cells to Organisms 3 Eukaryotic cell was a giant leap forward in the early history of life
lectures -> Id is nothing new latest attempt to put a modern face on some very old ideas is old wine in new bottles…
lectures -> The Discovery of Time
lectures -> The Discovery of Time We have made great progress in discovering the history of life on Earth
lectures -> Origin of Life 3 How could a system as complex as a living cell get started?
lectures -> Dinosaur Renaissance Most young boys (and many young girls!) play with dinosaurs


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