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 waterOxygen:- 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