Origin of Solar System & Earth

Origin of Solar System & Earth Chapter 2

What does this have to do with oceanography? • Where does water come from? • Why do we have oceans? • Why do we have life as we know it? • Elemental composition • Present day configuration relative to origins • Hydrological cycle • Dissolved gases/Ocean and Atmosphere

Time • Importance of time scales • Forces at work in the past • Forces at work today • How can we measure age of the earth

How old is Earth? • Biblical scholars of 19th century (Bishop Ussher) – 6000 years (started at 4004 BC) • Classical Greeks – infinite – history endlessly repeats itself • Mayans believed earth recycled on a 3000 year time scale • Han Chinese thought earth was recreated every 23,639,040 years • The age we now except may change but is consistent with current theory

More recent efforts • Lord Kelvin - 80 million years old – based on cooling of molten Earth • Darwin - really old based on time for natural selection (biological argument) • Hutton – really old based on uniformitarianism (processes in the past taking place at rates comparable to today) (geological argument)

Earth’s age • Earth is about 4.5 (or 4.6) BY old • First 700 MY Earth was a spinning cloud of gas, dust and planetoids • These condensed and settled to solidify into a series of planets • Since that time, geological history and evolution commenced.

The Big Bang Theory • Currently the dominant theory • First iteration proposed by Georges Lemaître in 1927. He observed the red shift in distant nebulas and invoked relativity. • Hubble found experimental evidence (1929) – galaxies are moving away from us with speeds proportional to their distance. • Theory suggested because it explains the expansion & predicts the existence of cosmic radiation (leftover photons) & nucleosynthesis • 1964 cosmic radiation discovered (Arno Penzias & Robert Wilson who won the Nobel Prize)

Big Bang – what is it? • All mass and energy concentrated at a geometric point • ~14 or 15 BY ago • Beginning of space and time • Expansion/cooling of universe began • Protons and neutrons form • Cooling initiated the formation of atoms (nucleosynthesis) – first mostly H (the most abundant form of matter in the universe)

Formation of galaxy and stars • Galaxy – rotating aggregation of stars, dust, gas and debris held together by gravity • Stars are massive spheres of incandescent gases • 100’s of billions of galaxies in the universe and 100’s of billions of stars in the galaxies • Sun is a star • Sun plus its family of planets is our solar system • Our solar system formed about 5 BY ago

Our galaxy is out in a spiral arm • Our solar system orbits the galaxy’s core • (230 million year orbit at 280 km/s)

Stars • Stars form in nebulae, large diffuse clouds of dust and gas. • Condensation theory – spinning nebula starts to shrink and heat under its own gravity • Protostar – condensed gases • At temperature of ~10 million degrees C, nuclear fusion begins (H’s fuse to form He) which releases energy and stops shrinkage • Star is stable once fusion reactions begin (form atoms as heavy as C and O)

Beginning of the end • Star starts consuming heavier atoms increasing energy output and swelling to a “red giant” • Incinerates planet and throws off matter including heavy elements • More massive stars get hotter and consume H at higher rates and make heavier atoms (e.g., Fe)

The end • H is consumed • Core collapses on itself • Internal temperatures sore so can no longer contract • Cataclysmic expansion called a supernova (30 sec) • Mass is accelerated outward • Forces holding apart atomic nuclei are overcome • Heavier atoms formed

Our Solar System • Our solar nebula was struck by a supernova • Caused our condensing nebula to spin • Introduced heavy atoms to seed the formation of planets • 5 BY ago, the solar nebula was 75% H, 23% He and 2% other material • Center became protosun • Outer material became planets – smaller bodies that orbit a star but do not shine by their own light

Planets • Grew by accretion – big clumps use gravitational pull to accrete condensing matter • Near sun, first materials to solidify had higher boiling points (metals and rocky minerals) – Mercury is mostly Fe, Ni. Inner rocky planets. • Next Mg, Si, H2O and O2 condensed (plus some Fe and Ni). Middle planets (e.g., Earth). • CH4 and NH3 in frigid outer zones. Outer gassy planets (Jupiter, Saturn, Uranus and Neptune).

Stabilization of solar system • Protosun became star (sun) and nuclear fusion began • Solar wind (radiation) at the start of those reactions cleared excess particles and ended rapid accretion of inner planets.

Early Earth • Homogeneous throughout during initial accretion of cold particles • Surface heated by impacts (asteroids, comets and debris) • Heat, gravitational compression, radioactive decay caused partial melting. • Density stratification. Gravity pulled heavy elements to interior. • Friction during this produced more heat. • Lighter minerals (Si, Mg, Al and O-bonded compounds) migrated to surface forming Earth’s crust.

Later • Earth began to cool (first surface 4.6 BY ago) • Impact of planetary body (4.5 BY ago – metallic core fell into earth’s core and rocky mantle was ejected, condensed and formed our moon. • New atmosphere formed by outgassing • Hot vapor condensed to clouds (water) • Comet impacts added additional water

Formation of liquid water • Outgassing & cooling to form boiling rain (20 million years) • Additional cooling – water collected in basins • Water plus CO2 made carbonic acid which dissolved rocks (contributed salts) • More water from comets (~ meters in diameter) • Carbonaceous chondrites? • Later, addition of O2 caused oxidation reactions. • Most of the ocean in place by 4 BY ago • (new water is 0.1 km3/yr) • Unclear whether there were always continents

Gases expelled (outgassed) from volcanos formed new Earth atmosphere. • Composed mostly of CO2 and water vapor. • Clouds reflected about 60% of sunlight. • Clouds trapped lots of energy as well. • Water began accumulating in liquid form about 4.0 BYA forming earliest terrestrial oceans. Widespread volcanic activity released H2 and smaller quantities of CO2, Cl2, N2 and H2 which produced a water vapor atmosphere that also contained carbon dioxide (CO2), methane (CH4) and ammonia (NH3). As Earth cooled, the water vapor (1) condensed and (2) fell to Earth's surface. There it accumulated to (3) form the oceans.

Volume of Earth's mantle is 1027 cm3 (ave. density of 4.5 g/cm3). Total mass for mantle is 4.5 X 1027 g. Water of oceans has mass of 1.4 X 1024 g. Mantle lost 0.031% of mass as water to have produced oceans.

Water from comets • -measure about 9 m (30 ft) in diameter. • -enter atmosphere at rate of about 20/second. • At the observed rate of occurrence, Earth would receive 0.0025 mm of water per year. • Four billion years of such bombardment would give enough water to fill the oceans to their present volume. Recorded by ultraviolet photometer aboard the satellite Dynamic Explorer 1. The dark spot or 'hole', thought to be caused by the vaporization of cometlike balls of ice, is shown in the inset. The dark holes in the atmosphere were 48 km across and existed for up to 3 minutes. Because of the absorption spectra of these dark spots, they can be explained only by the comet-like balls of ice breaking up and vaporizing 1600-3200 km above Earths surface.

Current Ocean Statistics • 97.5 % of water on earth is in the ocean • 2.5 % of water is on land (primarily as ice) • 0.01% is surface and atm water!

More stats • Total area of oceans now is 71% of Earth’s surface • Avg depth is 3800 m • Mean sphere depth is 2430 m • depth at which amount of surface above and below that depth are equal • Avg temperature is 4oC (= 39oF; cold) • Volume 1.4 billion km3

Early Atmosphere • 4.5 to 3.5 BY ago. Rich in CO2, N2, H2O and some CH4 and NH3. • 3.5 BY ago began shift toward today’s atmosphere (mostly O2 and CO2) • Chemical weathering: CO2 dissolves in SW to make carbonic acid (acid dissolved rocks releasing minerals) & photochemical reactions with atmospheric H2O • About 2 BY ago, get introduction of O2 into atmosphere (after oxidation reactions). • Current atm - 21% O2 - 78% N2 - 0.04% CO2 ~0.9% Argon

Origin of Life • ~ 3.5 BY ago • Definition – self-replication? • Capable of growing more complex; obtains energy by breaking down chemical compounds • Water is ideal medium for life (retains heat, moderates temperature, dissolves chemicals, transports nutrients) • Source of building blocks • Primordial soup (mixture of H2Ovapor, NH3, CH4 and H) • Extraterrestrial – meteorites & comets • Carbonaceous chondrites have C in the form of organic compounds including amino acids

Becoming an organism • Need building blocks plus energy • Surface pools – biosynthesis • Concentration of organic matter on surfaces of clay minerals or bubbles; energy from sunlight • Deep ocean • Geothermal energy supplied by hydrothermal vents and H2S

Oldest known fossil (3.5 BY) from NW Australia • Life altered the atmosphere • First bacteria – anaerobic • Green algae – evolved from cyanobacteria • Photosynthesis uses CO2 and evolves O2 • Stromatolites – clusters of algae Oscillatoria today

Fossil algae 2 billion years old (left) and living algae (right). Note the similarities in appearance. Interspersed among the living algae are chains of rod-shaped bacteria. • First fossil life – bacteria-like forms (>3.8 BY ago). • Earliest forms were heterotrophs (organic compounds). • Autotrophs eventually evolved (Oxidized inorganic compounds through chemosynthesis).

Two billion year old fossilized stromatolites from the shores of Great Slave Lake, North-West Territories, Canada. • Photosynthesis: • 6H2O + 6CO2 + Sunlight <---> C6H12O6 + 6O2

Fate of early atmosphere • Green plants produced O2 and removed CO2 • C from air became locked up in sedimentary rocks and dissolved into the oceans • NH3 and CH4 reacted with atmospheric O2 • N2 was released from reactions of NH3 with O2 and from denitrifying bacteria. • O2 built up forming ozone (filtering out UV rays and allowing more evolution)

Timeline (since big bang) • 10-35 sec ABB (The Big Bang) • The universe is an infinitely dense, hot fireball. • 10-6 sec ABB (1 millionth of a second) • Universe forms: Expansion slows down; universe cools and becomes less dense • The most basic forces in nature become distinct: first gravity, then the strong force, which holds nuclei of atoms together, followed by the weak and electromagnetic forces. By the first second, the universe is made up of fundamental particles and energy: quarks, electrons, photons, neutrinos and less familiar types. These particles smash together to form protons and neutrons.

3 sec ABB • Formation of basic elements • Protons and neutrons come together to form the nuclei of simple elements: hydrogen (1 proton), helium (2 protons) and lithium (3 protons) (1, 2 and 3 in periodic table). It will take another 300,000 years for electrons to be captured into orbits around these nuclei to form stable atoms. • 10,000 yr ABB • Radiation Era • The first major era in the history of the universe is one in which most of the energy is in the form of radiation -- different wavelengths of light, X rays, radio waves and ultraviolet rays. This energy is the remnant of the primordial fireball, and as the universe expands, the waves of radiation are stretched and diluted until today, they make up the faint glow of microwaves which bathe the entire universe.

300,000 yr ABB • Matter dominates • The energy in matter and the energy in radiation are equal. As universe expands, waves of light are stretched to lower and lower energy, while the matter travels onward largely unaffected. Neutral atoms are formed as electrons link up with hydrogen and helium nuclei. Microwave background radiation gives us a direct picture of how matter was distributed at this early time. • 300 MY ABB • Birth of stars and galaxies. • Gravity amplifies slight irregularities in the density of the primordial gas. Even as the universe continues to expand rapidly, pockets of gas become more and more dense. Stars ignite within these pockets, and groups of stars become the earliest galaxies. (Still perhaps 12 to 15 billion years before the present).

5 BY ago Birth of the Sun • The sun forms within a cloud of gas in a spiral arm of the Milky Way Galaxy. A vast disk of gas and debris that swirls around this new star gives birth to planets, moons, and asteroids . Earth is the third planet out. • The image on the left, from the Hubble Space Telescope, shows a newborn star in the Orion Nebula surrounded by a disk of dust and gas that may one day collapse into planets, moons and asteroids. • 3.8 BY ago Earliest Life • The Earth has cooled and an atmosphere develops. Microscopic living cells, neither plants nor animals, begin to evolve and flourish in earth's many volcanic environments. • 700 MY ago Primitive Animals appear • These are mostly flatworms, jellyfish and algae. By 570 million years before the present, large numbers of creatures with hard shells suddenly appear. • 200 MY ago Mammals appear • The first mammals evolved from a class of reptiles that evolved mammalian traits, such as a segmented jaw and a series of bones that make up the inner ear.

65 MY ago Dinosaurs become extinct • An asteroid or comet slams into the northern part of the Yucatan Peninsula in Mexico. This world-wide cataclysm brings to an end the long age of the dinosaurs, and allows mammals to diversify and expand their ranges. • 600,000 yr ago Homo sapiens evolve • Our earliest ancestors evolve in Africa from a line of creatures that descended from apes. • 170,000 yr ago Supernova 1987a explodes • A star explodes in a dwarf galaxy known as the Large Magellanic Cloud that lies just beyond the Milky Way. The star, known in modern times as Sanduleak 69-202, is a blue supergiant 25 times more massive than our Sun. Such explosions distribute all the common elements such as Oxygen, Carbon, Nitrogen, Calcium and Iron into interstellar space where they enrich clouds of Hydrogen and Helium that are about to form new stars. They also create the heavier elements (such as gold, silver, lead, and uranium) and distribute these as well. Their remnants generate the cosmic rays which lead to mutation and evolution in living cells. These supernovae, then, are key to the evolution of the Universe and to life itself.

1054 Crab Supernova appears • A new star in the constellation Taurus outshines Venus. Chinese, Japanese, and Native American observers record the appearance of a supernova. It is not, however, recorded in Europe, most likely as a consequence of lack of study of nature during the Dark Ages. The remnants of this explosion are visible today as the Crab Nebula. Within the nebula, astronomers have found a pulsar, the ultra-dense remains of a star that blew up. • 1609 Galileo builds first telescope • Five years after the appearance of the great supernova of 1604, Galileo builds his first telescope. He sees the moons of Jupiter, Saturn's rings, the phases of Venus, and the stars in the Milky Way. • 1665 Newton describes gravity • At the age of 23, young Isaac Newton realizes that gravitational force accounts for falling bodies on earth as well as the motion of the moon and the planets in orbit. This is a revolutionary step in the history of thought, as it extends the influence of earthly behavior to the realm of the heavens. One set of laws, discovered and tested on our planet, will be seen to govern the entire universe.

1905 Einstein’s Theory of Relativity Relativity recognizes the speed of light as the absolute speed limit in the universe and, as such, unites the previously separate concepts of space and time into a unified spacetime. Eleven years later, his General Theory of Relativity replaces Newton's model of gravity with one in which the gravitational force is interpreted as the response of bodies to distortions in spacetime which matter itself creates. Predictions of black holes and an expanding Universe are immediate consequences of this revolutionary theory which remains unchallenged today as our description of the cosmos.

1929 Hubble discovers universe is expanding • Edwin Hubble discovers that the universe is expanding. The astronomer Edwin Hubble uses the new 100-inch telescope on Mt. Wilson in Southern California to discover that the farther away a galaxy is, the more its light is shifted to the red. And the redder a galaxy's light, the faster it is moving away from us. By describing this "Doppler shift," Hubble proves that the universe is not static, but is expanding in all directions. He also discovers that galaxies are much further away than anyone had thought. • 1960 Quasars discovered • Allan Sandage and Thomas Matthews find sources of intense radio energy, calling them Quasi Stellar Radio Sources. Four years later, Maarten Schmidt would discover that these sources lie at the edge of the visible universe. In recent years, astronomers have realized that they are gigantic black holes at the centers of young galaxies into which matter is heated to high temperatures and glows brightly as it rushes in. • 1964 Microwave radiation discovered • Scientists at the Bell Telephone Laboratories discovered microwave radiation that bathes the earth from all directions in space. This radiation is the afterglow of the Big Bang.

1967 Discovery of Pulsars • A graduate student, Jocelyn Bell, and her professor, Anthony Hewish, discover intense pulsating sources of radio energy, known as pulsars. Pulsars were the first known examples of neutron stars, extremely dense objects that form in the wake of some supernovae. The crab pulsar, is the remnant of the bright supernova recorded by Native Americans and cultures around the world in the year 1054 A.D. • 1987 Light from supernova 1987 reaches Earth • The light from this supernova reaches earth, 170,000 years after is parent star exploded. Underground sensors in the United States and Japan first detect a wave of subatomic particles known as neutrinos from the explosion. Astronomers rush to telescopes in the southern hemisphere to study the progress of the explosion and perfect models describing the violent deaths of large stars.

1990 Hubble launched • The twelve-ton telescope, equipped with a 94-inch mirror, is sent into orbit by astronauts aboard the space shuttle Discovery. Within two months, a flaw in its mirror is discovered, placing in jeopardy the largest investment ever in astronomy. • 1990 Big Bang confirmed • Astronomers use the new Cosmic Background Explorer satellite (COBE) to take a detailed spectrum of the microwave background radiation. These studies showed that the radiation is in nearly perfect agreement with the Big Bang theory. Two years later, scientists used the same instrument to discover minute variations in the background radiation: the earliest known evidence of structure in the universe. • 1993 Hubble optics repaired • Hubble's greatest legacy so far: detailed images of galaxies near the limits of the visible universe.

Future • 100 Trillion • Astronomers assume that the universe will gradually wither away, provided it keeps on expanding and does not recollapse under the pull of its own gravity. During the Stelliferous Era, from 10,000 years to 100 trillion years after the Big Bang, most of the energy generated by the universe is in the form of stars burning hydrogen and other elements in their cores. • 1037 yrs • Most of the mass that we can currently see in the universe is locked up in degenerate stars, those that have blown up and collapsed into black holes and neutron stars, or have withered into white dwarfs. Energy in this era is generated through proton decay and particle annihilation.

1038 to 10100 The Black Hole Era • After the epoch of proton decay, the only stellar-like objects remaining are black holes of widely disparate masses, which are actively evaporating during this era. • 10100 Dark Era Begins • At this late time, protons have decayed and black holes have evaporated.Only the waste products from these processes remain: mostly photons of colossal wavelength, neutrinos, electrons, and positrons. For all intents and purposes, the universe as we know it has dissipated. From: PBS Online (http://www.pbs.org/deepspace/timeline/)

Aging the Earth & Solar System • Dating meteorites, chunks of rock and metal, formed about the same time as the sun and planets and from the same cloud. • Carbonaceous chondrites are a class of meteorites believed to be the most primitive in the solar system (silicate minerals, water and carbon) • Dating moon rocks and oldest rocks found on Earth (about 3.8 BY old) • Rate of expansion (2002, astronomers had very accurate measurements and calculated backwards to an age of 13-14 BY old).

How do we age things? • Isotopic decay • Radioisotopes are unstable and decay to form daughter products which form next to parent nuclide. • Know the ratio of daughter to parent in undisturbed sample and the rate of conversion (e.g., decay rate or half-life) allows computation of age • This has been done with several isotope pairs to arrive at age of solar system

Isotopes • The ordinary isotope of hydrogen, H, is known as Protium, the other two isotopes are Deuterium (a proton and a neutron; stable) and Tritium (a protron and two neutrons; unstable). Hydrogen is the only element whose isotopes have been given different names. • Radioactive decay – spontaneous disintegration of unstable nuclei • For low atomic number elements stable is about 1:1 neutrons:protons in the nuclei. For higher atomic number elements, the ratio is about 1.6:1. • Heavy nuclides (atomic number > 82) have no stable configuration. • Different types of decay • FYI: Fusion of hydrogen into helium provides the energy of the hydrogen bomb

Some isotopes *daughters are smaller and contain fewer protons, neutrons & electrons

Doppler shifting • Wavelengths emitted by objects moving away are shifted to lower frequency (towards reds) • Wavelengths emitted by objects moving towards us are shifted to higher frequency. • Example of sound – pitch of fire engine is higher as truck moves towards you and lower as it moves away) • For galaxies outside our group, the redshift is known as hubble expansion (after Edwin Hubble who discovered this phenomenon in 1929).

Another way to look at time • 0-7 No record (no baby pics) • 8-12 First rocks formed that are preserved today • 12 First living cell appeared • 22-23 Oxygen appeared • 31 Atmosphere becomes oxygenated • 40 First fossils formed (earlier records are dubious) • 41 First vertebrates • 41.7 First land plants • 43 First reptiles • 45 First flowering plants • 45.6 Mammals, birds, insects became dominant • 25 days ago First human ancestors • 0.5 hours ago Civilization began • 1 min ago Industrial revolution began Geologic Time – Appendix II

Origin of Solar System & Earth