2Why are planets close to the Sun, such as Earth, rocky with thin atmospheres, while those far from the Sun, such as Jupiter, are gaseous with thick atmospheres?JUPITER vs. EARTH
3Earth’s Origin Is Described by the Solar Nebula Hypothesis The Sun is a star at the centre of our Solar System -one of billions in the Milky Way GalaxyThe Solar System formed approx-imately 4.6 byaThe Sun and other objects originated from the collapse and rotation of a nebula“bya” means “billions of years ago” – another way to write that is Ga = giga-annum
4Nebulas A Nebula is a cloud of gas and dust Planetary nebula remaining mineral particles and gas after a star explodesA Nebula is a cloud of gas and dustStars release energy and build elements through nuclear fusionStars “burn” their hydrogen becoming brighterEventually, stars become Red Giants and explode!Which elements are formed during the normal evolution of a star?Which are formed during a supernova explosion?NOVAS = exploding starsSUPERNOVAS = really big exploding starsButterfly nebula3800 light years away
5The Solar System began with the collapse and condensation of a Planetary Nebula Abundant carbon dioxide, methane, and ammonia. These are volatile gases most stable in outer region.Suggested tips to give students: Copernican heliocentrism is the name given to Nicolaus Copernicus’ theory (published in 1543) that the Sun was in the center of the Universe. Volatile gases = easily evaporated. The planetesimal hypothesis of Viktor Saranov, states that planets form out of dust grains that collide and stick to form larger and larger bodies. It is highly recommended to focus on the introduction to Section 2-2 for a more complete explanation.Rocky particles and metallic compounds formed solids in the inner region (Terrestrial Planets)Outer region (cooler) solids formed of hydrogen compounds, metals, and rocks (Gas Giants)Transition zone between the two regions is known informally as the “frost line”Nuclear fusion in core released Solar Wind and stopped contraction
6Planetesimal accretion rocky particles and gases coalesce into planetsApproximately 5 bya, a swirling nebula began to collapse inward under the pull of gravity
7The Solar System consists of: 8 planets5 dwarf planetsnumerous small solar system bodies240 known satellites (moons)Countless particles and interplanetary gas moleculesEarth, the Sun, and other objects in the Solar System originated at the same time from the same source and have evolved in varying ways since then.Why is Pluto no longer considered to be one of the main planets?
8Our Sun: A Massive Hydrogen Bomb held together by gravity The solar core is site of nuclear fusion4 H atoms are forced together to form 1 He, which has less massMass differential is expelled as energy (light and heat)The Sun is getting “lighter” (less mass) and hotter through timeIt has enough fuel to last another 4 to 5 billion yearsHow much hotter is the sun now than it used to be 4 bya?
9Terrestrial planets are small and rocky, with thin atmospheres MERCURY VENUS EARTH MARSTerrestrial planets are small and rocky, with thin atmospheres
10Mercury Venus EARTH Mars Atmosphere: 42% O2, 28% Na, 22% H2, 6% He, 5% KExtreme daytime heat, extreme nighttime coldVenusAtmosphere: Carbon dioxide 96.5% CO2, 3.5% N2Even hotter than Mercury due to high percentage of CO2EARTHAtmosphere: 78.09% N2, 20.95% O2, 0.93% Ar, 0.39% CO2,variable H2OHot, energy-providing core with surface cool enough for liquid H2OMarsAtmosphere: 95.3% CO2, 2.7% N2, 1.6% Ar, 0.13% O2Most Earthlike with dry river channels indicating waterSuggested tips to give students: Geologists worldwide are analyzing photographs taken by the Mars Rover to discern the characteristic features of sedimentary rocks – see Chapter 8 andInitially the Earth had an atmosphere similar to those of Venus and Mars. In what way has it changed and why?
11Gas Giants are massive planets with thick atmospheres. JupiterNeptuneBy volume, Jupiter is larger than all of the other planets combined.How many times larger is it (by volume) than the Earth?UranusSaturnEarth to the same scale
12JUPITER SATURN URANUS NEPTUNE Atmosphere: 89.8% H2, 10.2% HeThird-brightest object in the night sky after the Moon and VenusSATURNSaturn’s Atmosphere: 96.3% H2, 3.25% HeOblate due to a high rate of rotationURANUSAtmosphere: 82.5% H2, 15.2% He, 2.3% CH4The only planet that does not rotate perpendicular to the eclipticNEPTUNENeptune’s Atmosphere: 80% H2, 19% He, 1.5% CH4Inner two-thirds are likely composed of a mixture of molten rock,water, liquid ammonia, and methaneSuggested tips to give students: Geologists worldwide are analyzing photographs taken by the Mars Rover to discern the characteristic features of sedimentary rocks – see Chapter 8 andIn reference to Uranus, what do we mean when we say “does not rotate perpendicular to the ecliptic”, and why might this be the case ?
13What makes a comet’s tail? Other ObjectsOther objects in the Solar System include:Dwarf PlanetsCometsAsteroidsWhat makes a comet’s tail?Comet exhibiting coma (tail)
14Dwarf Planet“an object in the Solar System that orbits the Sun and is not a satellite of another planet or other celestial body. It must be spherical (or nearly so) in shape.”
15The Five OFFICIALLY RECOGNIZED Dwarf Planets HAUMEA, MAKEMAKE and PLUTO (with its moon, Charon)located in the Kuiper BeltPluto’s Atmosphere: 98% N2, < 1% H2O, < 1% CH4, < 1% COPluto and Charon considered a “double-dwarf”.ERISlocated in the scattered disk regionCERESa large asteroid located in the asteroid belt
16Why are asteroids and comets not spherical like the planets? Rocky, metallic planetesimals.CometsIcy (water ice and other frozen liquids or gases) planetesimals.Two views of Eros10 kmWhy are asteroids and comets not spherical like the planets?
18EARTH’S interior was hot to begin with (due to collisions) but it got even hotter because of nuclear fissionAn atmosphere was created by volcanic outgassing and delivery of gases and water by ice-covered comets.“Hadean Era”Suggested tips to give students: Hadean derives from Hades, Greek for ”Underworld” or “Hell”, referring to the conditions on Earth at the time. The geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks.
19Earth’s Geomagnetic Field The magnetic field is created by motion of the Earth’s liquid outer core, and blown into a streamlined shape by the Solar wind
20WHAT ABOUT THE ORIGIN OF THE MOON? Capture hypothesis:Fission hypothesis:Earth’s gravity captured a passing planetesimalCentrifugal force associatedwith Earth’s spin caused a bulge of material to separate from EarthDouble planet hypothesisImpact hypothesis:Earth and the Moon were formed concurrently from a local cloud of gas and dustEarth suffered a massivecollision with a Mars-sizedobject ejecting parts ofEarth’s mantle and coreinto orbit
21Impact Hypothesis Most widely accepted hypothesis of moon formation What are some of the characteristics of the Earth and Moon that support this hypothesis?