Chapter 2: Origins.

Chapter 2: Origins

Ch.2 Vocabulary to define:
Accretion Nebula Big bang Outgassing Biosynthesis Planet Condensation theory Protostar Density Solar nebula Density stratification Solar system Galaxy Star Milky Way galaxy Supernova

I. Stars and Seas --The origin of the ocean is linked to the origin of the Earth, the origin of the Earth is linked to the origin of the solar system and the galaxies.

--Stars turn H and He into larger elements, and spread these larger elements around when they
explode.

--The ocean was formed by water vapor escaping from the outer layers of the forming Earth.

--More water may have come in from comets crashing into the unprotected Earth.

II. The Origin of Earth --Theories of the age of the ocean, Earth, and the universe have only arisen within the last 50 years.

--Hypotheses have been made for how matter is assembled, how stars and planets are formed, and how life has arisen. Recent discoveries uphold these hypotheses.

--The big bang occurred approximately 15 billion years ago.

--We still don’t know what caused the explosion that led to the expansion of the universe.

--The early universe was so hot that atoms could not even form.

--1 million years after the big bang, temperatures cooled enough for H to form.

--1 billion years after the big bang, matter began to congeal into the first galaxies and stars.

a. Galaxies and Stars --matter aggregated into rotating galaxies

--our galaxy is called the Milky Way

--galaxies can look like discs with curved arms, ellipses, or be totally irregular in shape

--made of stars composed of H gas superheated into plasma

--there are 100 billion galaxies in the universe

--each galaxy can have 100 billion stars

--closest star to our sun is 26 trillion miles away (Alpha Centauri)

--our star, Sol, is a medium sized star

--we are ¾ of the way out from the galaxy's core on one of the spiral arms

--takes us 230 million years to go around the galaxy

--travelling half a million miles per hour around the galaxy

--Earth has been around the galaxy 20 times since the oceans formed

b. The Lives of Stars --large dust clouds (nebulae) in galaxies responsible for making stars

--telescopic evidence has shown us different levels of development with nebulae in our galaxy and others

--condensation theory comes from these observations

--nebula shrinks and heats up due to weak gravity

--protostar forms and gravity gets stronger

--when 10 million°C is reached, nuclear fusion occurs and H changes to He, giving off even more energy

--protostar becomes a star when it stops compressing

--star remains stable for a time, fusing elements into larger elements like O and C

--star death depends on star size

--medium sized stars like ours begin to burn the C and O and swell into a red giant

--larger stars form Fe, and collapse, causing a supernova

--supernova lasts about 30 sec, but create larger elements, shooting them out into space

c. The Formation of the Solar System
--our solar system was created by the leftovers of a supernova

--the explosion caused our protogalaxy to spin, and provided heavier elements

--our planets, our bodies, all the atoms in our solar system came from a large dying star

--our solar nebula, 5 billion years ago, was 75%H, 23%He, 2% heavier elements, gases, dust, and ice

--as condensation occurred, the nebula spun faster, and material concentrated near the center and became the protosun

--outer material became the planets by accretion

--closest to the sun, heavier elements like metals, along with heavy rock, solidified, forming the inner planets

--farthest from the sun, lighter elements and gases condensed or accumulated into the outer gas giants

--Earth, being in the middle, is made of rocky metals and gases

--accretion took roughly 30 to 50
million years

--energy released from protostar to star transformation blew the dust away, so accretion stopped

--more than 100 other planets have been discovered

III. Earth and Ocean --early Earth probably homogeneous

--melted due to collisions, accretion, radioactive element accumulation

--heavier iron and nickel pulled inward causing more heat

--lighter elements rose to the surface, forming the crust

--density stratification took 100 million years

--first surface formed about 4.6 billion years ago

--early Earth hit by Mars size object, it’s core melding with ours, it’s mantle shot out into Earth orbit, accreted into our moon

--first atmosphere blown away by solar radiation

--second atmosphere created by outgassing

--early Earth too hot for water to settle on the surface, it stayed in the atmosphere

--rain boiled when it hit the hot surface, but eventually cooled

--heavy ocean forming rains lasted about 20 million years

--vapor and other gases continued to leak out from underground

--ocean forming caused crust to grow thicker

--new studies suggest Earth was completely covered in water for 200 million years

--most of the ocean was in place 4 billion years ago, but formation continues today due to outgassing of volcanic steam

--early atmosphere was CO2, N2, H2O(g), NH3, and CH4

--3.5 billion years ago, gases changed to more of today’s composition

--1.5 billion years ago, plant ancestors started making O2

IV. The Origin of Life --Life on Earth is primarily due to the presence of so much water

--Life arose from accumulations of C compounds, brought by early collisions

--Experiments have duplicated formation of organic molecules, protolife

--only works without O2

--because saline water is such a big part of all living things, life is thought to have begun in the oceans

--early sun so cool that ocean was probably frozen 1000 feet down (remember that ice is less dense, so it floats)

--C compounds thought to form under ice, protected from harmful chemicals and extreme cold

--life could not arise today (discuss why not with a neighbor) ________________________________________________________________

--earliest fossils between 3. 4 and 3
--earliest fossils between 3.4 and 3.5 billion years old, bacteria-like impressions

--fossils from 3.85 bya show complex C compounds, only a few hundred million years after stable ocean formed

--recent studies show hydrothermal vents may be where life first originated

V. The Distant Future of Earth?
--our sun has about 5 billion years left

--too small for supernova, red giant will engulf the inner planets

--Earth will be absorbed into the star and shot out as recycled material into space

VI. Comparative Oceanography
--H2O not rare in space, but water as a liquid is extremely rare

--our orbit is perfect for liquid water

a. Jupiter’s Moons

--Europa found to have an ice covered surface with an ocean underneath with 40x more water than our oceans

--Ganymede has water too

b. Mars --possible ocean beds from 3.2 to 1.2 bya, when temperatures were hotter

--water thought to have been lost into space from its thin atmosphere

c. Saturn’s Big Moon

--Titan shown to have an ocean of liquid methane, ethane, and other hydrocarbons, and a “continent” of water ice

d. Extrasolar planets --water vapor, methane, and ammonia on extrasolar planets 2003—100 known extrasolar planets 2011—694 known

e. Life and Oceans? --since O2 is so reactive, it would require some source of production to keep replenishing the oxygen

--free O2 could be a cue that life does or has existed on newly discovered extrasolar planets

Chapter 2: Origins.

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