The Earth and Other Planets

The Earth and Other Planets Our Solar System Sun / Terrestrial Planets / Jovian Planets TERRESTRIAL PLANETS Mercury Venus Earth Mars The terrestrial planets all tend to be fairly small, have few moons, and are solid and rocky.

The Earth and Other Planets JOVIAN PLANETS Jupiter Saturn Uranus Neptune The jovian planets all tend to be quite large, have several moons, are primarily made of layers of gases which become denser further down, and may have a small solid core.

The Earth and Other Planets NEBULAR THEORY Theory re formation of solar system: As dust and gas clouds collected due to gravitational forces, they began to rotate and flatten into a disk. The majority of mass collected in the center, and the planets began as mass concentrations orbiting the dense central body. Where did the dust and gas clouds come from? Many believe the dust and gas originated in the events that occurred when the universe first formed. How old is our solar system? Approximately 4.5 billion years old.

The Earth and Other Planets DEBRIS THAT DID NOT BECOME PLANETS Asteroids Small Rocky In a “belt” between Mars and Jupiter Comets Ice and dirt Circle the sun outside of Pluto Halley’s comet is best known Meteors Small pieces of debris Orbit the sun Burn if fall into earth’s atmosphere Meteorite A piece of rock big enough to reach earth’s surface .

The Earth and Other Planets THE EARTH’S MOTION Revolves around sun Travels in an elliptical orbit Takes approximately 365 days to complete 1 orbit Rotates on axis Angle of rotation tilts 23° Takes approximately 24 hours to complete 1 spin Precesses Spinning on axis in a circular pattern Completes circular pattern once every 23,000 years THE EARTH’S MOON Orbits earth Has synchronized rotation and revolution with earth Takes approximately 1 month to complete 1 orbit Phase of moon is based on how mush of lighted side we can see Has 1/6 of the gravitational pull of the earth Mutual gravitational influence Pull on earth’s surface waters creates tides

The Earth and Other Planets THE EARTH’S MOTION Revolves around sun Travels in an elliptical orbit Takes approximately 365 days to complete 1 orbit Rotates on axis Angle of rotation tilts 23° Takes approximately 24 hours to complete 1 spin Precesses Spinning on axis in a circular pattern Completes circular pattern once every 23,000 years THE EARTH’S MOON Orbits earth Has synchronized rotation and revolution with earth Takes approximately 1 month to complete 1 orbit Phase of moon is based on how mush of lighted side we can see Has 1/6 of the gravitational pull of the earth Mutual gravitational influence Pull on earth’s surface waters creates tides

The Earth and Other Planets THE EARTH’S INTERIOR CRUST Outer layer 6 to 45 miles thick Made of lightest materials Solid Approximately 70% covered with water MANTLE Below crust High temperatures Solid in upper region, thick liquid of melted rock below Widest layer OUTER CORE Below mantle Very high temperatures Liquid Iron – nickel INNER CORE At the earth’s center Extremely high temperatures Solid due to tremendous pressure Primarily iron, some nickel

The Earth and Other Planets HOW “LIFE” ON EARTH BEGAN GEOLOGIC TIME FRAME (see Time Scale shown in text, p. 631) Covers the 4.5 billion years of Earth’s existence Life not possible initially due to high temperatures, lack of proper atmosphere, no available water, continuous bombardment from space As earth cooled and impacts lessened, land and sea formed First living organisms appeared in oceans about midway through the earth’s history Gradually oxygen began to accumulate in atmosphere Ozone layer began to form Life forms appeared on land less than 500 million years ago Principal vertebrate life froms on earth were reptiles fro 65 million to 250 million years ago Mammals began to dominate the earth in the last 65 million years Human ancestors first appeared less than 2 million years ago HUMAN TIME FRAME Modern human species less than 50,000 years old Recorded human history available for past 4000 years only Human influence on the earth’s ecosystems which support life insignificant until the Industrial Era beginning 250 years ago