NATS1311 110906 bw

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Information about NATS1311 110906 bw

Published on January 11, 2008

Author: Desiderio


Slide1:  Launched in June-July 2003 Arrived on Mars January, 2004 Named Spirit and Opportunity by Sofi Collis, the 3rd grader - seen here with a life-size model. Primary mission - look for evidence of past water. Mars Exploration Rovers Rover Landing Sites :  Rover Landing Sites Spirit was sent to Gusev Crater. Pictures taken by other spacecraft looked to Mars scientists like the site once had a lake. Opportunity was sent to a place that was made of different rock than any other place on the surface of Mars - a type of rock usually made in water. Slide3:  Spirit’s sent back picture of a flat, dusty plain from its landing site. Opportunity landed in a small meteor crater. Both found strong evidence of ancient water on Mars (to be discussed in a future lecture). Slide4:  Jovian Planets Outer planets visited by few spacecraft - Neptune and Uranus only by Voyager 2 flybys - visited Jupiter, Saturn, Uranus, and Neptune during great planet line-up of the 1980’s - only time in hundreds of years possible. Voyager 2 now about twice as far as Pluto - nearing Oort cloud - still transmitting data Slide5:  Galileo Spacecraft The Galileo spacecraft arrived at Jupiter in 1995 after a 6-year journey. Very convoluted trajectory with multiple planetary flybys for gravitational boost assistance. Dropped probe into Jupiter atmosphere. Flew into Jupiter at end of life in 2003. Slide6:  Cassini Spacecraft The Cassini spacecraft arrived at Saturn in 2004 after a 7-year journey. Like Galileo, it had a very convoluted trajectory with multiple planetary flybys for gravitational boost assistance - now providing some of the most spectacular images and data ever as it orbits the planet. Also dropped a probe into Titan’s atmosphere. Slide8:  Jupiter The first of the Jovian planets - largest in the solar system - 1000 Earths could fit inside. No solid surface - primarily hydrogen and helium. Dynamic weather systems with colorful latitudinal bands, atmospheric clouds and storms - the cloud patterns change within hours or days. Slide9:  The Great Red Spot A long lived storm - several hundred years old - large enough to swallow two or three Earths. Slide10:  Aurora on Jupiter Slide11:  The Jovian System Jupiter has over 60 moons. Slide12:  Ganymede - larger than Mercury - may have a subsurface ocean Io - the most volcanically active place in the solar system Slide13:  Volcanoes on Io Caused by tidal heating created by tremendous gravitational pull of Jupiter. Slide14:  Saturn Second largest planet - only slightly smaller diameter than Jupiter but much less dense - about 1/3 the mass of Jupiter . The most spectacular planet with its beautiful rings. (All four Jovian planets have rings but Saturn’s are the only ones visible through a small telescope.) Slide15:  Saturn’s Rings Composed primarily of small particles of rock and ice - this is a picture from the Cassini spacecraft that arrived at Saturn in June after a seven-year journey. The Cassini Division Slide16:  The Saturn System Saturn has over 30 moons. Slide17:  Titan - Saturn’s largest moon - larger than Mercury. Blanketed by a thick atmosphere - only moon in the solar system with one. Thought to be similar to conditions on Earth when life first formed. Mimas - the ‘Death Star”. Collision with large asteroid nearly destroyed Mimas and created the “Darth Vader” crater Slide18:  Titan’s Atmosphere Slide19:  Aurora on Saturn Slide20:  The last picture that Voyager 2 took before departing for Uranus and Neptune. Slide21:  Uranus Much smaller than Jupiter but still larger than Earth. Relatively featureless - pale blue-green color caused by methane gas. Uranus is tipped on its side compared to the other planets - probably the results of a cataclysmic collision early in its lifetime. Slide22:  The Uranus System Uranus has over 21 moons. Slide23:  Ariel - long rift valleys stretch across the entire surface - canyons much like the ones on Mars - appear as though they have been smoothed by a fluid. Fluid could not have been water - water acts like steel at these temperatures. Flow marks possibly made by ammonia, methane or even carbon monoxide. Titania - largest moon of Uranus. Slide24:  Neptune Last of the Jovian planets. Similar to Uranus only bluer. A dynamic planet with several large, dark spots reminiscent of Jupiter’s hurricane-like storms. The largest spot - the Great Dark Spot - is about the size of the earth and is similar to the Great Red Spot on Jupiter. Has the strongest winds on any planet. Slide25:  Triton Largest moon of Neptune. Coldest world in the solar system - about -450ºF - reflects more sunlight than Pluto. Only moon with retrograde motion - orbits in opposite direction of Neptune’s rotation. Indicates was probably captured. Slide26:  Pluto and Charon Unlike any of the planets - made up mostly of ices. Highly elliptical orbit - actually comes inside Neptune’s orbit. Recently declared not a planet. Slide27:  The Formation of the Solar System Origin of the Solar System:  Origin of the Solar System Theory must explain the data Large bodies in the Solar System have orderly motions. There are two types of planets. small, rocky terrestrial planets large, hydrogen-rich Jovian planets Asteroids and comets exist in certain regions of the Solar System There are exceptions to these patterns. Slide29:  Theories of Solar System Formation The nebular hypothesis - Our solar system formed from gravitational collapse of an interstellar cloud of gas First proposed by German philosopher Immanuel Kant (1755) and French mathematician Pierre-Simon Laplace (1795) Close encounter hypothesis - solar system formed from debris left over from a near-collision of Sun and another star Gained popularity in first half of 20th century Discarded - could not account for observed orbital motions neat division of planets into two categories Required highly improbable event - inconceivable it could have accounted for many other stars now known to have planets Slide30:  Nebular Theory – our Solar System formed from a giant, swirling cloud of gas and dust. Depends on two principles of Physics: Law of Gravity gravitaional potential energy  heat Conservation of angular momentum and Basic chemistry The Solar Nebula:  The Solar Nebula The nebular theory holds that our Solar System formed out of a nebula which collapsed under its own gravity. observational evidence We observe stars in the process of forming today. The are always found within interstellar clouds of gas. newly born stars in the Orion Nebula solar nebula – name given to the cloud of gas from which our own Solar System formed Gravitational Collapse:  Gravitational Collapse The solar nebula was initially somewhat spherical and a few light years in diameter. very cold rotating slightly It was given a “push” by some event. perhaps the shock wave from a nearby supernova As the nebula shrank, gravity increased, causing collapse. As the nebula “fell” inward, gravitational potential energy was converted to heat. Conservation of Energy As the nebula’s radius decreased, it rotated faster Conservation of Angular Momentum Slide33:  Original cloud large and diffuse - began to collapse. Final density, shape, size, and temperature the result of three processes: Heating - cloud heated up due to conservation of energy - as cloud shrank, gravitational energy converted to kinetic energy - collisions converted KE into random motions of thermal energy - density and temperature greatest at center Spinning - conservation of angular momentum caused rotation to increase as cloud collapsed - all material didn’t collapse to middle because the greater the angular momentum of a cloud the more spread out it will be. Flattening - cloud flattened to a disk - different clumps of gas collided and merged - random motion of clumps became average motion - became more orderly flattening original cloud’s lumpy shape - orbits also became more circular Slide34:  Collapse of Solar Nebula Animation Slide35:  Formation of Protoplanetary Disk Animation Flattening of the Solar Nebula:  Flattening of the Solar Nebula As the nebula collapsed, clumps of gas collided and merged. Their random velocities averaged out into the nebula’s direction of rotation. The spinning nebula assumed the shape of a disk. Slide37:  Formation of Protoplanetary Disk By the time solar nebula had shrunk to 200 AU, became flattened, spinning disk - called a protoplanetary disk The Sun formed in the very center of the nebula. temperature & density were high enough for nuclear fusion reactions to begin The planets formed in the rest of the disk. Three processes - heating, spinning, flattening - produced orderly motions. Explains: all planets lie along one plane (in the disk) all planets orbit in one direction (the spin direction of the disk) the Sun rotates in the same direction the planets would tend to rotate in this same direction most moons orbit in this direction most planetary orbits are near circular (collisions in the disk) Strong Support for the Nebular Theory:  Strong Support for the Nebular Theory Computer simulations can reproduce most of the observed motions We have observed disks around other stars. These could be new planetary systems in formation. AB Auriga  Pictoris Slide39:  After Big Bang hydrogen and helium (with a little Lithium) only elements present. Heavier elements produced in stars - very heavy elements produced in massive stellar explosions - contents scattered - coalesce to form new stars and planets. Most of matter in universe still hydrogen and helium - 98% of solar system made up of these two elements Galactic Recycling Slide40:  Stellar Jets Forming stars often emit jets of gas out their north and south poles Building the Planets:  Building the Planets Condensation – process in which solid or liquid particles form in a gas Elements and compounds began to condense (i.e. solidify) out of the nebula. Created “seeds” around around which gravity could ultimately build planets. Condensation of different materials dependent on temperature. Slide42:  Temperature in solar nebula dependent on distance from center - In innermost regions where Sun formed, temperature greater than 1600 K - too hot for condensation - remained gaseous Within Mercury’s orbit temperature less than 1600 K - metals could condense Near Mercury’s orbit temperature less than 1300 K - rock could condense - condensation increased as distance from center increased Near asteroid belt, carbon rich materials plus minerals with small amount of water could condense Beyond asteroid belt was frost line - temperature less than 150 K - hydrogen compounds condensed into ices - abundance of seeds much greater due to abundance of hydrogen - three times as much as metal and rock combined Slide43:  So only rocks and metals condensed within 3.5 AU of the Sun - the so-called frost line. Hydrogen compounds (ices) condensed beyond the frost line. Therefore, temperature distribution - not gravity - resulted in formation of terrestrial and Jovian planets - orbit of particle does not depend on size or density The Frost Line Slide44:  Temperature Distribution of Disk Animation Slide45:  accretion - process of growth by colliding and sticking together - small grains stick to one another via electromagnetic force - static electricity - until they are massive enough to attract via gravity to form: planetesimals - pieces of planets - sizes and composition reflect seeds from which they were accreted combine near the Sun to form rocky planets combine beyond the frostline to form icy planetesimals which… capture H/He far from Sun to form gas planets Small planetesimals can have almost any shape - small asteroids and comets. Larger planetesimals become more spherical under influence of gravity - planets and moons. Accretion Slide46:  Accretion and Formation of Planets Animation

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