Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44NSCI 314LIFE IN THE COSMOS6 - The Formation of the Earth, the Early Earth, and the Origin of Life Dr. Karen KolehmainenDepartment of Physics, CSUSBhttp://physics.csusb.edu/~karen/1. 1. Interstellar gas and dust cloud (initially about 1 light year in diameter) starts to collapse gravitationally. a. Rotation speeds up due to conservation of angular momentum. b. Cloud flattens into a disk.c. Temperature increases, more so towards the center.d. Sun forms in the center.1. 2. Solar nebula: a rotating disk about 100 AU in diameter 1. 3. Condensation and accretion: dust particles form condensation nuclei and grow due to collisions.a. At distances less than 2-3 AU out from the sun, only rocky and metallic materials condense.b. Beyond about 3 AU, it's cold enough for water ice particles to condense.c. Even farther out, where it's even colder, ammonia and methane ice particles condense.OUTLINE OF SOLAR SYSTEM FORMATION•4. Billions of planetesimals are formed. These are rock, metal, and/or ice bodies up to a few kilometers across. 1. 5. The larger planetesimals are massive enough to attract each other gravitationally. They are pulled together, collide, and coalesce to form protoplanets and protomoons up to a few hundred kilometers across. 1. 6. Gravitational accretion of gas: the largest protoplanets in the cool outer parts of the solar nebula pull in gas, adding to the planet’s mass. In the hotter inner solar nebula, the gravitational pull of the protoplanets isn’t strong enough to hold onto the fast-moving gas molecules. (The molecules are moving faster than the escape velocity from the protoplanet.) Most of the smaller protomoons don’t have enough gravitational pull to hold onto gas molecules, even in the cool outer parts of the nebula.1. 7. As a result of steps (3) and (6), compositions of planets and moons vary, resulting in: a. Outer planets that have rocky/metallic cores surrounded by thick gaseous atmospheres.b. Moons of outer planets that are made of ice and rock, with thin or no atmospheres.c. Inner planets that are composed of rock and metal, with thin or no atmospheres. – 8. Cooling off: planets cool off as heat is radiated into space.a. They are hot initially because of the “heat of formation,” i.e., the heating during gravitational contraction.b. Rocky and metallic materials solidify once temperature is low enough.c. Radioactive decay of materials in the interior continues to provide a source of heat.d. The smaller the planet or moon, the more quickly it cools. The larger the planet or moon, the more slowly it cools. Therefore, larger planets or moons will remain hot inside for a longer time than smaller planets and moons.9. Cleaning up: over the course of about 500 million years, the debris left over from the solar system formation is cleared.a. Some of the remaining planetesimals collide with planets or moons (leaving visible impact craters on anything with a solid surface).b. The outer planets strongly influence the orbits of many of the remaining planetesimals (comets), throwing them into new orbits much farther from the sun (forming the “Oort Cloud”). c. Inner planets obtain their atmospheric gases and water from outgassing (the escape of trapped gases via volcanic activity) and the impact of cometary material.d. The gravitational effects of Jupiter (the most massive planet) influence the region of the asteroid belt (between Mars and Jupiter) so that some material remains in stable solar orbit but is unable to coalesce into a larger body.FORMATION OF THE EARTHFORMED (ALONG WITH THE SUN AND THE REST OF THE SOLAR SYSTEM) OUT OF A NEBULA 4.6 BILLION YEARS AGOVERY HOT INITIALLY DUE TO HEAT OF FORMATIONMOLTEN AT FIRST, THEN COOLED & SOLIDIFIED & DIFFERENTIATED (SEPARATED INTO LAYERS)NO ATMOSPHERE INITIALLY – HOT ENOUGH THAT GAS MOLECULES WERE MOVING FAST ENOUGH TO ESCAPE FROM EARTH'S GRAVITYATMOSPHERE AND WATER ADDED LATER VIA OUTGASSING AND COMETARY IMPACTSDIFFERENTIATIONEARTH WAS COMPLETELY MOLTEN FOR THE FIRST 100 MILLION YEARSDENSER MATERIALS SANK TO THE CENTER RESULT IS A LAYERED STRUCTURE–CORE: MOSTLY IRON AND NICKEL, INNER PART IS SOLID AND OUTER PART IS MOLTEN–MANTLE: SEMI-MOLTEN ROCKY MATERIAL (PRIMARILY SILICON AND OXYGEN)–CRUST: THIN SOLID LOWER-DENSITY ROCKY MATERIAL, CONTINENTAL CRUST IS THICKER (BUT LOWER DENSITY) THAN SEAFLOOR CRUST PROPAGATION OF SEISMIC (EARTHQUAKE) WAVES ARE USED TO MAP OUT INTERNAL STRUCTUREPLATE TECTONICSINSIDE OF THE EARTH IS STILL HOT INSIDECORE HEATS MANTLE FROM BELOW, CONVECTION PRODUCES SWIRLY CIRCULATION PATTERNSCONVECTION IN A FLUID MEANS HOT FLUID RISES AND COOL FLUID SINKSPLATES IN CRUST FLOAT ON SEMI-LIQUID MANTLE AND MOVE DUE TO CIRCULATION UNDERNEATH –CONTINENTS MOVE WITH TIME–SEAFLOOR SPREADING – WHERE PLATES MOVE APART AT MID-OCEAN RIDGES, MANTLE MATERIAL RISES TO TOP AND COOLS, PRODUCING NEW CRUST –SUBDUCTION – WHERE PLATES COLLIDE, ONE IS PUSHED UNDER THE OTHER AND ITS MATERIAL IS RECYCLED BACK INTO MANTLE–MOUNTAIN RANGES CAN BE PRODUCED WHEN PLATES COLLIDE–EARTHQUAKES PRODUCED WHEN PLATES MOVEMAGNETIC FIELDALL MAGNETIC PHENOMENA ARE ULTIMATELY CAUSED BY MOVING ELECTRIC CHARGES.AN ELECTRIC CURRENT (ELECTRONS FLOWING THROUGH A MATERIAL) CREATES A MAGNETIC FIELD.AN ELECTRICALLY CONDUCTING MATERIAL (e.g., A METAL) THAT IS MOVING CAUSES A MAGNETIC FIELD (BECAUSE OF THE MOVING CHARGES IN THE MATERIAL).AS THE EARTH ROTATES, THE MOLTEN IRON IN THE OUTER CORE SWIRLS AND SLOSHES, PRODUCING THE EARTH'S MAGNETIC FIELD.IF A PLANET HAS A MAGNETIC FIELD, IT MUST HAVE SOME KIND OF ELECTRICALLY CONDUCTING MATERIAL INSIDE OF IT.BOMBARDMENTEARTH (AND OTHER PLANETS AND MOONS) BOMBARDED BY LEFTOVER PLANETESIMALS, PRODUCING IMPACT CRATERSMANY CRATERS STILL VISIBLE ON EARTH’S MOON AND SOME OTHER INNER PLANETSON EARTH, MOST CRATERS WERE EVENTUALLY ERODED AWAY BY WATER AND WIND, OR ERASED BY SUBDUCTIONIMPACTS OF COMETS AND ASTEROIDS ADDED MOST LIGHT ELEMENTS (HYDROGEN, CARBON, NITROGEN, AND OXYGEN), WATER, AND PERHAPS ORGANIC MOLECULESFORMATION OF EARTH’S MOONNO OTHER INNER