Download 7.3 Earth and Life

7.3 Earth and Life
Formation of the Solar
System
Formation of the Solar System
Scientists claim
that 4.5 billion
years ago there
was just a
featureless cloud
of gas..mostly
hydrogen and
some helium with
a little carbon and
iron
Continued…
• No one knows what started this gas cloud or how
it came into being…
• Some believe it was from a wave from a near by
Supernova?...gathering gas into a clump called a
protostar…..which eventually became our Sun
• Left over…too distant material to be pulled into
the ‘clump” became the planets….?
• Begs the question…yet again…where did the gas
come from!!!!
Very similar to
the Pearson
text book
diagram Fig
7.3.1 pg. 238
Structure of the planets
• Planets are split into two categories:
– Terrestrial (rocky) planets: Mercury, Venus,
Earth, and Mars. Made from heavier
elements that gathered close to the Sun
– Gas Planets: Jupiter, Saturn, Uranus and
Neptune.
– Made from elements light enough to stay
well clear of the Sun.
Planets have similar structure, despite varying
elements due to the same formation process
Structure contd:
• Gravity did not finish once the planets
had begun
• It continued to pull elements towards
the centre of each planet…forms a dense
core
• Core surrounded by a number of layers
lower in density
• Earth and Jupiter are typical of the
planets in their individual categories.
Earths Structure
How do we know this is the
structure?
• Some information gained from volcanoes
• Deep mineshafts
• And indirectly from earthquakes and the Earths
magnetic and gravitational fields
– The energy from an earthquake’s seismic waves
means it can felt at various points around the
earth at different times
– The waves don’t travel through the earth…but are
reflected and refracted as they go from one
internal layer to another
– This has helped scientists determine the thickness
and composition of layers within the earth
Magnetic Field:….
• The shape and nature of the Earths magnetic
field also gives some clues as to the internal
structure
• We don’t know how the field is generated..but
we do know there has to iron rich material in
the mantle and inner-core
• Other planets in the solar system exhibit
gravitational and magnetic fields-noted as
spacecraft fly past and their instruments are
affected- plus photos show ongoing geological
activity over time
Jupiter
• Mainly gas
• Rocky core
The Moon
• Moons are natural satellites as they orbit
planets
• All planets but Mercury and Venus in our
system have a moon (s)
• Earth’s Moon is unusual for 3 reasons:
– It is large compared to the size of earth, ¼
Earth's Diameter, 5th largest in the solar system
– Moon is a lot less dense than most other rocky
moons- it does not have an iron core
– Samples reveal moon rock is similar to earth
rock
How did the moon
form?
• It is Suggested that the earth was struck by a
Mars size planet called Theia and bits of
Earths mantle were thrown into space to form
the moon
• The iron core of Theia sank into the Earth and
became our core……explains the moons size
and composition being similar to Earth’s?
• This is the Giant Impact Hypothesis
How did life begin on Earth?
• All living things are made of carbon,
hydrogen and oxygen
• These elements are also found in rocks!
But in simpler arrangements
• Despite we may see this as the hand of a
creator! Scientists continue to search for
answers based on physical, testable
evidence
The creative Spark!!!!!!!
• Abiogenesis- Harold Urey and Stanley Miller
1950’s
• Life from inanimate objects-using a mixture of
gas that matched the Earths original
atmosphere to see if life could be created
• They did produce amino acids- the building
blocks of proteins and then the building blocks
of DNA-so they did form organic compounds
form inorganic material…but not life as such
Seeds of Life…….
• Back to our geological evidence! That stated that
the 1st living organisms developed only 100
million years after the earth.
• This doesn’t comply with the theory just
mentioned----- they suggested life came to earth
by way of microorganisms trapped in comets or
meteorites: THE PANSPERMIA THEORY
• Supported by the fact that tardigrades have been
discovered
Tardigrades
• No…not late grades on your report!
• Microorganisms that can survive even the
vacuum of space
• Called water bears?
• Also organic compounds have been
discovered in space
• Amino acids in the tails of comets and
polycyclic aromatic hydrocarbons have been
discovered in gases in interstellar space
Interstellar ( between the star systems
in a galaxy)- gas cloud-Milky way
Astrobiology
• Study of life in parts of the universe
other than Earth
• To discover life elsewhere would
mean scientists could test their
theories like panspermia…
• However life began…..on Earth…it is
evident that Earth supports life
because:
• 1. the orbit around the sun makes Earth
habitable-close enough to keep water liquid
and encourage photosynthesis
• Far enough away to keep surface Earth
temperatures also habitable
• Ocean tides are believed to have allowed early
water based organisms to adjust to living on
dry land and day and night patterns created
the environment for the nocturnal creatures
• Meteorites etc. have struck the earth in the
past and killed lost of species- offering the
opportunity for new ones to develop?????
The Atmosphere
• Early atmosphere: came from volcanic
eruptions and comet impacts
– Comet impacts provided water
Oxygen:- back to the cyano- bacteria- one celled
organisms that developed the ability to capture
sunlight and produce hydrocarbons with carbon
dioxide and water….
The oxygen produced from the process….became
atmospheric oxygen over many…many years.
Cyanobacteria and iron formations
Prac 7.3
Averaging
density pg 243