12.16.12 final review


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12.16.12 final review

  1. 1. Planetesimal EjectionLarger “debris” leftover from creating the planets are eithercaptured as moons of the larger planets, or the gravity of theplanets guides the debris into the asteroid belt, Kuiper belt, orOort cloud.
  2. 2. Asteroids and meteoroids are smallobjects made of mainly rock andmetal. They are found primarily inand around the Inner Solar System.The only difference between the twois size. Asteroids are all larger than100 meters in diameter, or have amass more than 10,000 tons -meteoroids are smaller.
  3. 3. Inner Solar System Asteroids and meteoroids are usually found near the plane of the solar system. Those orbiting between Mars and Jupiter are in the asteroid belt, while those in Jupiter’s orbit are in the Trojan regions.Some of these asteroids and meteoroids come closer to theSun. Those that cross the orbit of Earth are called Apolloasteroids.
  4. 4. A meteor is seen when any comet, asteroid, or meteoroidenters the Earth’s atmosphere. The “shooting star” you seeis a meteor.A meteorite is the chunk of rock or metal that has reachedthe surface of the Earth from space.A meteoroid is a small chuck of rock or metal that orbitsthe Sun
  5. 5. Why does this asteroid look“weathered”?Like a rock you might find on abeach?Everything gets hit by meteoroids!
  6. 6. Meteor Trail
  7. 7. Barringer Crater Meteoroids are constantly hitting the Earth. Most of these meteoroids are the size of grains of sand or so. They make short quick meteor trails visible only at night. Usually you can see about 1 or 2 an hour. Larger meteors are very rare.Big meteoroid strikes like the one that produced Barringer Crater(the meteoroid was about 50 meters across and hit with anenergy of few megatons of TNT) occur once every few thousandyears.
  8. 8. Tunguska Debris The most recent event was in 1908 in Tunguska, Siberia. We are not sure if the object was a meteoroid or a comet, but it exploded in midair with an energy of about 20 to 40 megatons of TNT!We think that asteroid impacts are even more rare. We guessthat they occur once every 600,000 years or so. Such impactswould be large enough to cause global climate changes - a“nuclear winter”.
  9. 9. The leading theory about theextinction of the dinosaurs ofcourse involves an asteroid impact.All over the world you can seeevidence for this in the K-Tboundary in geologic strata(layers).
  10. 10. CometsUnlike asteroids and meteoroids, comets are made up of ices -frozen water, CO2, and possibly other lighter gasses - and alsorock and dust. As the ices evaporate off the comet, a cloudcalled the coma is formed around the nucleus. The solar windand radiation pushes the gas and dust away from the nucleus toform the tail.
  11. 11. Halley’s Comet Closeup
  12. 12. Comet Tails There are usually two tails for a comet, and ion tail and a dust tail. The ion tail is made of ionized comet material and is pointing directly away from the Sun. The dust tail is curved as the dust particles orbit around the Sun after getting released by the comet.
  13. 13. Meteor Showers As Earth passes through the debris path of a comet, observers on Earth can see many many meteors coming from the same general area of the sky. These meteor showers or storms are often named for the constellation that they seem to “come from”.
  14. 14. Comet Reservoirs We believe that most objects in the Kuiper Belt and Oort cloud are made of ices and rock. Since they are so far form the Sun, even oxygen and nitrogen will turn to ice!Long period comets are thought to mainly come from theOort cloud.Short period comets (like Halley’s) are thought to come fromthe Kuiper belt.
  15. 15. The Discovery of PlutoAfter the discovery of Neptune,astronomers still thought another planetmight (but they were wrong) beinfluencing the orbits of Uranus andNeptune. In 1930 Clyde Tombaughdiscovered Pluto while looking for thisnew planet. Pluto is the only planet wehave not explored with a spacecraft. TheNew Horizons craft should get there in2015!
  16. 16. Pluto and CharonPluto and its moon are both probably Kuiper Belt objects. Bymeasuring their size and mass we can calculate their density. Fromthis we believe are mainly made up of rock and ice, very similar toEuropa, Ganymede, Callisto and Triton.
  17. 17. PlutoA fuzzy map of Pluto made from Hubble Telescope images.
  18. 18. The Hubble telescope has just recently discovered two new moonsaround Pluto. In 2006 they were given the names of Nix and Hydra.The appear to be in the same plane as Charon, so their formationshould be related.
  19. 19. KBOs ComparedIn the last few years several Kuiper Beltobjects have been found. And severaleven have their own moons.There are at least 11 KBOs withdiameters of 1000 km or more. M. Brown/Keck Observatory
  20. 20. Pluto’s DemotionRESOLUTION 5AThe IAU therefore resolves that planets and other bodies in our SolarSystem, except satellites,be defined into three distinct categories in thefollowing way:(1) A "planet"1 is a celestial body that (a) is in orbit around the Sun, (b)has sufficient mass for its self-gravity to overcome rigid body forces sothat it assumes a hydrostatic equilibrium (nearly round) shape, and (c)has cleared the neighbourhood around its orbit.(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun,(b) has sufficient mass for its self-gravity to overcome rigid body forces sothat it assumes a hydrostatic equilibrium (nearly round) shape2, (c) hasnot cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects3, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".IAU - INTERNATIONAL ASTRONOMICAL UNION web site - http://www.iau2006.org/mirror/www.iau.org/iau0602/index.html
  21. 21. Planet XAstronomers once thought that another large planet (Earth sizeor bigger) might exist far out in the Kuiper belt or Oort cloud.In fact Pluto was found searching for planet X. Such a planetcould disrupt the orbits of objects out there, and send them intoward the inner Solar System, where we see them as comets.So far we have no evidence that “planet X” exists. However wehave searched only a small fraction of the Kuiper Belt, and knoweven less about the Oort cloud.
  22. 22. Stellar Balance Our Sun lives in a state of balance.... between the force of gravity pushing in.... and the pressure from fusion pushing out.
  23. 23. Solar Composition ChangeAs stars burn Hydrogen into Helium the amount of Heliumin the star’s core builds up.At this point in the star’s life the temperature in its core is nothigh enough to fuse Helium into other elements, so theHelium just sits there inert.
  24. 24. Solar Composition ChangeWhen the amount of Helium builds up to acertain level, fusion at the center of the corestops, with fusion only occurring in a shellsurrounding the non-burning Helium.
  25. 25. The center of the core is now nolonger beingpushed out by the energy producedfrom fusion. As the amount of Helium“ash” grows, gravity starts tocompress it.As the core is compressed thetemperature goes up until Helium canbe fused.Since the temperature of the core is much higher than before,the core is producing a lot more energy. This extra energy“pushes out” the rest of the star and the star getsbigger!So as the core gets smaller the rest of the star gets larger!
  26. 26. We see manydifferent stars in ourgalaxy. Some starsare enormous RedGiants that arehundreds of timeslarger than our Sun.Will our Sun everbecome a Red Giant?YES!How? When?
  27. 27. Red GiantWhen this happens toour Sun in about 4billion years our Sun willexpand to possiblyengulf the Earth!
  28. 28. Now Helium is being fused into Carbon, and the processrepeats, the core shrinks and gets hotter, but our Sun isnot large enough for Carbon fusion to start…
  29. 29. G-Type Star EvolutionThroughout the stars life, as the star uses up its fuel, the corecontinues to shrink, the core temperature continues to rise,and more and more energy is being emitted by the core, andthe star gets larger and larger until…
  30. 30. PlanetaryNebulae
  31. 31. White Dwarf on H–R DiagramAfter all the fuel isgone, and the starhas made a nebula,all that is left is aWhite DwarfThis is the leftovercore of the old star, itis very small (Earthsized) and very hot
  32. 32. White dwarfs shine only due to stored heat, asthey cool they grow fainter and fainter.Eventually (trillions of years from now) theywill be cold enough to stop emitting lightaltogether,
  33. 33. If the star is massive enough the temperature in the core of thestar can get high enough (1 billion K) to start the fusion ofCarbon into heavier elements like Aluminum, Neon, andSodium. When this happens, the core shrinks again and thestar expands again.
  34. 34. Stars that are massive enough to produce temperatures upto 4 billion K can burn all the elements up to Iron in theircores.These stars can grow up to 1000 times the size of our Sun- Supergiants!
  35. 35. Heavy Element Fusion Iron is the stopping point for any star, fusing Iron into heavier elements does not release energy. Fusion still continues around the iron core, which keeps growing.In the iron core, there is no fusion to create an outward pressureto counteract the force of gravity.
  36. 36. Core collapse supernova The iron core of the star that is about the size of the Earth. The iron in the core is made up of ... protons (+) neutrons (0) electrons (-)Most of the space inside an atom is taken up by the electrons.When the Iron core of a star reaches critical mass called theChandrasekhar mass (1.4 times the mass of our Sun) theforce of gravity is too great and the protons and electrons get“squeezed” together to make neutrons.
  37. 37. Core collapse supernova Now the core of the star is made up of just neutrons (0) !!! Without electrons around to take up space, gravity can cause the core to collapse.In about 1 minute or so the core (that was supporting theweight of the entire star) collapses from the size of the Earth tothe size of Chicago (~10 miles across). The rest of the starcollapses onto the core and then “bounces”.
  38. 38. Supernova 1987AThe core becomes a Neutron star and we see a Supernova!This core-collapse supernova is also called a type II supernova.
  39. 39. Over the time period of just a few days, a supernova canemit as much energy as our Sun will in its 10 billion yearlifetime.
  40. 40. Supernova Light Curves Astronomers can tell the two types of supernovae apart by looking at how bright the supernova is over a period of time.Also astronomers can distinguish the two types by looking at aspectrum and seeing how much hydrogen was present in theexplosion. A type I (carbon-detonation) supernova has verylittle hydrogen present, unlike a type II (core-collapse)supernova.
  41. 41. Supernova RemnantsIn our galaxy we estimatethere is a type I and a type IIsupernova about once every100 years. The last one thatwe saw in our galaxy was in1604....so we are due!We do see supernovae quiteoften in other galaxies.
  42. 42. Supernova 1987AThis supernova was theclosest in recent history,and the only one where wewere able study itaccurately.
  43. 43. Neutron Stars Neutron stars are extreme objects Density: 1015 g/cm3 Temperature: 1012 K when born Magnetic Field: 1012 times stronger than Earth’s Spin: from 60 rpm to 38,000 rpm
  44. 44. Curved Space Newton’s Law of Gravity: The force between mass m1 and mass m2 is.... F = Gm1m2/R2 So if an object has no mass, there should be no force on it due to gravity! Einstein: Mass causes space itself to curve and warp, and objects travel on this surface....
  45. 45. Tests of General RelativityThe first test of Einstein’s theory of general relativity camewhen we measured how the gravity of our own Sun can bendlight.
  46. 46. Gravitational RedshiftThe gravity of a blackhole is so strong, thatlight can not escape!The region where this istrue is inside the eventhorizon.The event horizon isNOT the surface of theblack hole. It is just theboundary betweenwhere light can escape,and where it can’t!
  47. 47. Black Holes Black holes are formed when you compress an object to a size smaller than the Schwarzschild radius for that object. For the Earth it is about 1 cm For Jupiter it is about 3 m For our Sun it is about 3 km.The only force strong enough that we know of to produce ablack hole is a type II (core-collapse) supernova. Even thenonly very massive stars will end up as black holes.
  48. 48. Black Holes If you were far from the black hole, you would feel no unusual effects. In fact if our Sun suddenly became a black hole the Earth would simply keep orbiting it like usual. As you approach a black hole the gravity gets stronger, and the tidal forces start to stretch you.If you could survive to come close to the black hole, you wouldobserve severe distortions in both space and time as predictedby Einstein!
  49. 49. Robot–Astronaut What is IN a black hole? We believe that all matter could be compressed to a singularity! A point of infinite density and zero size. BUT.... There is no way to find out!
  50. 50. The Solar System There are three kinds of objects in our Solar System (other than the Sun) Terrestrial planets Jovian planets and other stuff..... asteroids, comets, and meteoroids
  51. 51. Sun and Planets - Relative Sizes
  52. 52. This is the Eagle nebula as seen by the Hubble telescope. Fusion creates elements heavier than hydrogen and helium, and supernovae disperse these elements out into the galaxy. The dust and gas seen here is probably made up of gas from the Big Bang and also from many supernovae.This gas and dust is the raw materials that stars and solarsystems are made out of.
  53. 53. Right now, new stars and solar systems are being formed in this cloud of gas and dust. As intense radiation from stars just outside the cloud “blow” the cloud away, we can see small clumps of denser regions of gas and dust being revealed.In each of these clumps is a solar system that is forming, eachwith a sun that could someday be much like our own, and eachperhaps with planets like Earth.
  54. 54. It all starts with a cloud of gas and dust. The gravitationalattraction between the gas and dust particles slowly causesthe cloud to collapse, to contract. This causes all of thematter in the cloud to become more concentrated.Because the initial gas cloud had some rotation, as thecollapse happens this rotation speeds up, and the cloudflattens out into a disk.This is due to something called conservation of angularmomentum.
  55. 55. In the center of the disk the gravity is the strongest, so most ofthe mass in the solar system accumulates there. This willbecome a protostar. The rest of the material starts clumping together in orbit around this central mass. Larger clumps condense out of the gas and dust.
  56. 56. These clumps then start to join together in a snowballeffect. This forms planetesimals.
  57. 57. During this time a protostar hasformed. It is bigger than our Sun,but not as hot yet. The temperaturein the core is not hot enough forfusion to start. Once fusion starts, itbecomes a star!
  58. 58. Beta Pictoris
  59. 59. The Virial TheoremHow does the dust and gas in the cloud heat up as it collapses?A small part of the cloud that is far away from the center of thecloud has a lot of gravitational potential energy. As this small partof the cloud “falls” closer to the center, it loses potential energy andgains kinetic energy. It starts moving faster.However, the cloud is spinning, and the faster the small part of thecloud moves, the farther away from the center orbits.So how does the cloud collapse? The small part of the cloud needsto lose both potential and kinetic energy. It does this by turningpotential and kinetic energy into heat! Gas molecules and dustgrains hit each other, and these collisions turn kinetic energy intoheat and the temperature of the cloud goes up!
  60. 60. The Virial TheoremYou can derive an equation from Newton’s laws that shows howmuch energy the gas and dust will turn into heat as it slowly spirals intoward the center of the cloud.This equation is called the virial theorem.Basically what this means is that as matter collects to form a largeobject, like the Sun, Earth or even our Moon, the matter heats up tohigher temperatures.This is how the temperature in the center of our protostar got highenough (10 million Kelvin) for fusion to start.This is one of the reasons why the center of the Earth is hot enough tomelt metal.
  61. 61. The planetesimals in orbit around the protostar are still growinglarger, accumulating more and more material.Eventually the planetesimals all clump together and formprotoplanets! These have roughly the right sizes as our planetsdo today, but they are not quite done growing yet.
  62. 62. Temperature in the Early Solar NebulaBecause of the higher temperatures in the inner solar system theprotoplanets near the protostar were very different than thosefarther away. The near protoplanets were made of mostly rockand metal, with very little hydrogen, helium, oxygen, water,nitrogen, or other lighter chemicals The protoplanets that were farther out were made more out of the lighter chemicals. Since there were more of these lighter materials than anything else in the early solar system the outer planets became much larger.
  63. 63. When fusion starts and our Sun is born, it starts emitting hugeamounts of energy. The enormous amounts of radiation and solar wind that the new star produces “blows” or “pushes” away all of the dust and gas that is leftover from the production of the planets.http://sohowww.nascom.nasa.gov/
  64. 64. The new planets in the solar system looked nothing like whatwe see today.Planets were all very hot, the inner planets were allcompletely molten. The atmospheres of all the planets were mainly made of hydrogen and helium. The smaller planets like Earth didn’t have a strong enough gravity to hold on to this atmosphere for very long. The planets were undifferentiated - meaning they did not have different regions made of different materials.
  65. 65. Planetesimal EjectionLarger “debris” leftover from creating the planets are eithercaptured as moons of the larger planets, or the gravity of theplanets guides the debris into the asteroid belt, Kuiper belt, orOort cloud.
  66. 66. Comet Reservoirs
  67. 67. By learning about the Earth wecan make comparisons to theother planets and understandthem better.
  68. 68. The Earth Earth has a .... magnetosphere atmosphere hydrosphere crust mantle and an outer and inner core
  69. 69. Planetary Science All the different parts of the Earth .... - magnetosphere - atmosphere - hydrosphere - crust - mantle - core ... affect each other. The dynamics of how processes in these regions affect the planet is called Planetary Science.
  70. 70. Earth’s InteriorThe interior of the Earth is differentiated because the Earthwas completely molten at some point in its history.Both radioactivity and asteroid impacts supplied the heat tomelt the Earth.
  71. 71. Seismology Seismology is the study of how shock waves from earthquakes travel through the Earth. We can learn about the density of the interior of the Earth this way much like an ultrasound test can see inside peopleSudden changes in density can cause these wavesto be reflected or refracted. Seismic waves also canshow if the material is solid or liquid.
  72. 72. Earth’s InteriorFrom seismology we know that the Earth’s core is muchmore dense than the silicate based mantle and crust, andthe core is made of a solid center, and a liquid outer region. From the density measurements made using seismology we believe that the core is mostly made of iron, with some nickel
  73. 73. Plate DriftEarth is a very geologically active place with volcanoes andplate tectonics. The mantle is semi-molten, with convectionslowly causing hotter material to rise and cooler material to fallin the mantle. The tectonic plates of the Earth “float” on theseconvection currents.
  74. 74. Global Plates
  75. 75. SeismologyHere you see theseismic waves from the2004 Sumatraearthquake. You cansee how the seismicwaves could still bedetected even aftergoing around the worldalmost two times
  76. 76. Earth’s MagnetosphereMagnetohydrodynamics isthe study of how electricallyconductive fluids behave.Because the Earth’s core is arotating and convectingsystem of a metallic liquid,strong electrical currents areproduced in the Earth’s core.This produces the Earth’smagnetic field!
  77. 77. Earth’s MagnetosphereComputer calculations using magnetohydrodynamics haveshown that if a planet does not have• a conducting liquid• convection• and rotationThe planet will not have a strong magnetic field like the Earth’s.
  78. 78. Van Allen BeltsThe Earth’s magnetic field deflects and traps particles fromthe Solar Wind. The trapped particles are located in tworegions called the Van Allen belts.
  79. 79. Aurora BorealisSome of the Solar Wind makes it through the Earth’s magneticfield and hits our atmosphere making it glow. This usuallyhappens at the North and South poles – the Aurora Borealisand the Aurora Australis
  80. 80. Earth’s Atmosphere
  81. 81. ConvectionMost of Earth’s weather occurs in the troposphere. Weatheron Earth is driven by convection, warm air rising and colderair falling.
  82. 82. The Greenhouse Effect and Global Warming Over the last two decades evidence has been growing that the Earth’s atmosphere is getting warmer. Most likely this is due to human activity. It is possible that this rise in temperature is linked to the increase in “greenhouse gases” like CO2 in the atmosphere.
  83. 83. Greenhouse EffectThe Greenhouse effect refers to the “blanket like” effect thatcertain gases have.These gases absorb and re-emit infrared radiation, whichprevents this radiation from escaping to space so easily.
  84. 84. HydrosphereOcean currents – like the thermohaline current shown here –can have a profound effect on the climate by thetransportation of energy (heat) and matter (dissolved gasses).
  85. 85. Lunar Tides
  86. 86. Lunar Tides The force of gravity decreases with increasing distance. This is responsible for the tidal force effect. This effect causes the Earth to very slightly deform or be stretched by the moon’s gravity.Since water is more free to move than solid ground, we seethis effect mostly in the Earth’s oceans – the tides.In the open ocean this effect is quite small only abouta 1 meter high bulge.
  87. 87. Solar and Lunar TidesThe Sun also produces atidal effect on the Earthbut it is much smallerthan the moon’s effect.The largest tides are theSpring tides when theSun, Moon, and Earthare all roughly in a line.The smallest tides arethe Neap tides when theMoon and Sun are atright angles to the Earth.
  88. 88. Tidal Bulge The Tides on Earth are not directly in line with the Moon. Since the tidal bulge is offset, the Moon can affect the Earths rotation, and the Earths rotation can affect the Moon’s orbit! This is causing the Earth’s rotation to slow down, and the Moon to mover farther away from the Earth.
  89. 89. Tidal BulgeJust like the moon produces atidal bulge on Earth, the Earthmakes a tidal bulge on the moon.Over time the effect of Earth’sgravity on the moon’s tidal bulgechanged the rotation of the moon.This is why the same side of themoon always faces the Earth.This is called tidal locking. TheMoon’s orbit and rotation aretidally locked or synchronized.
  90. 90. Tidally locked meansthat the time it takesfor the Moon to rotateis the same as thetime it takes to orbitthe Earth. So we canonly see one side ofthe Moon from Earth.
  91. 91. Tidal BulgeThe Earth’s rotation is not yetsynchronized with the Moon’sorbit. The Earth’s rotation willkeep slowing down, and theMoon will keep moving awayuntil they become tidallylocked, and only one side ofthe Earth will face theMoon.... many billions ofyears from now.The Earth’s rotation is slowingat a rate of 0.002 seconds percentury and the Moon ismoving away 3.8 cm per year.
  92. 92. Full Moon, Near Side There are two different kinds of surfaces on the near side of the moon. Maria – flat, darker regions that are made of younger material. Produced by lava flows. Highlands – older, lighter colored regions with many mountains and craters
  93. 93. Full Moon, Far Side On the far side we find mainly just highlands and very few maria.
  94. 94. The Moon Since the moon is differentiated, it too was molten at some time in its history. However not a lot is known about the interior of the moon. We believe that the core of the Moon is no longer molten.
  95. 95. Moon, Close Up When the Moon was younger and its crust was thinner and its interior still molten, we believe that the crust cracked and lava flowed up through these cracks and formed the maria.
  96. 96. Meteoroid Impact
  97. 97. Lunar Surface A layer of dust covers the surface of the Moon. This dust is caused by the many, many impacts of meteoroids that continually occur on the Moon.
  98. 98. Lunar The dominant theory of howFormation our Moon formed is the Impact Theory – which says a protoplanet about the size of Mars hit the Earth shortly after the Earth formed
  99. 99. Lunar FormationA fraction of thedebris from thisimpact collectedtogether to form ourMoon.
  100. 100. The Terrestrial Planets
  101. 101. The Messenger spacecraftWe were not able to learn much about Mercury from Mariner10 (the only spacecraft to visit Mercury). The Messengerspacecraft is on its way to Mercury right now, it will do 3 flybysof Mercury in 2008 and 2009, and then go into orbit in 2011.Since Messenger is more modern and advanced than Mariner10, we will learn much much more.
  102. 102. Mercury’s RotationMercury’s rotation (59days) is tidally locked to2/3 of an orbital period(88 days). Its orbit androtation is notsynchronized like ourMoon’s becauseMercury’s orbit iseccentric (more ellipticalthan the orbits of mostplanets). This meansthat one “day” (fromnoon to noon) onMercury lasts 176 Earthdays!
  103. 103. 108
  104. 104. Because it is so smallthe core of Mercury isprobably mostly solid,meaning that scientistsdid not expect to find amagnetosphere!One the scale shown theEarth’s field wouldregister at around50,000nT, so we thinkthat something verydifferent is causingMercury’s magnetic field.
  105. 105. Mercury’s SurfaceMercury’s surface has a large number of these scarps or cliffslike giant cracks in its surface.Mercury never had plate tectonics like the Earth. When the crustof Mercury cooled it shrank causing the crust to crack.
  106. 106. Venus, Up Close Because of Venus’s dense cloud cover most of what we know about Venus’s surface and rotation comes from using radar. There has been only a few spacecraft to land on Venus, but each survived for only a short time.
  107. 107. The Atmosphere of Venus The atmosphere of Venus is made up of carbon dioxide, with clouds of sulfuric acid. The atmosphere is some 90 times denser than Earth’s. The Greenhouse effect causes the surface temperature of Venus to be close to 730K day or night.This is warmer than even Mercury which is a lot closer to theSun! Venus is far too hot for gases lighter than CO 2 to stay inits atmosphere. Venus has almost no water, O 2, or N2.
  108. 108. Venus Magellan Map In 1995 the Magellan spacecraft was able to make a much more detailed radar map of Venus. Possibly active shield volcanoes, craters, and volcanic structures called coronae were seen by Magellan.
  109. 109. Venus’s Surface Featurespictures from Magellanspacecraft NASA/JPL
  110. 110. Venus Corona and VolcanoesVenus has several times morevolcanoes as Earth does, howeverVenus does not have platetectonics like Earth. This could bewhy the surface of Venus appearsolder than Earth’s surface (~500million years vs. ~100 million). pictures from Magellan spacecraft NASA/JPLWe can not tell from these radarimages if Venus is geologicallyactive right now, but we believe itcould be active. We believe thatVenus is much like a “young” Earthwas just before Earth’s oceansformed.
  111. 111. VenusVenus has no detectable magnetosphere, probably due inpart to Venus’s very slow rotation rate and a lack ofconvection in the core.We expect Venus to have a crust, mantle and a core likeEarth
  112. 112. Venus in SituThis is one of the few pictures of the surface of Venus that wehave. There have only been 6 Russian landers (no US) eachlasting only an hour or two before running out of power.
  113. 113. Terrestrial Planets’ SpinWhile Venus is the planet that is closest in size to the Earth,Mars has a rotation rate (24.6 hours) and a tilted axis (24degrees) that are very similar to Earth.
  114. 114. Mars, Up CloseThe rovers have made manyrock and soil measurements.The main components of thissample were silicon, iron, andcalcium. The Martian soil isrich in iron, which is why is isred.
  115. 115. Mars Atmosphere Picture taken by Spirit of a sunset on Mars.Mars has a very thin atmosphere (less than 1% of Earth’s) ofmainly carbon dioxide. The surface temperature is around 50Klower than Earth’s, but would be colder without the greenhouseeffect.These temperatures were taken by a combination of the MarsGlobal Surveyor and the rover Opportunity.
  116. 116. Water on MarsBecause of orbiter pictures and geologic studies done by therovers we are now fairly confident that large amounts of liquidwater was present at some time on Mars.
  117. 117. Water on MarsNASA/JPL
  118. 118. Martian Outflow Where is all of this water now? Most of it was probably lost when Mars lost it’s atmosphere, but some of it might still be there, frozen under the surface.Scientists believe that because Mars is so small and so far fromthe Sun, that the planet cooled off much faster than the Earth did.When the core of the planet started to solidify it started to lose itsmagnetosphere. Mars lost almost all of its atmosphere due to acombination of being exposed to the Solar wind, and havingmuch weaker gravity than Earth.
  119. 119. Martian Outflow We have seen evidence for liquid water maybe existing on the surface of Mars recently.NASA/JPL/MalinSpace ScienceSystems
  120. 120. Life on Mars?We still do not have absolute proof that life existed onMars. But we think it is possible that it did long ago.
  121. 121. Planetesimal EjectionLarger “debris” leftover from creating the planets are eithercaptured as moons of the larger planets, or the gravity of theplanets guides the debris into the asteroid belt, Kuiper belt, orOort cloud.
  122. 122. Inner Solar System Most asteroids and meteoroids are usually found orbiting between Mars and Jupiter are in the asteroid belt.Some of these asteroids come closer to the Sun. Those thatcross the orbit of Earth are called Apollo asteroids.
  123. 123. Why does this asteroid look“weathered”?Like a rock you might find on abeach?Everything gets hit by meteoroids!
  124. 124. Barringer Crater Meteoroids are constantly hitting the Earth. Most of these meteoroids are the size of grains of sand or so. They make short quick meteor trails visible only at night. Usually you can see about 1 or 2 an hour. Larger meteors are very rare.Big meteoroid strikes like the one that produced Barringer Crater(the meteoroid was about 50 meters across and hit with anenergy of few megatons of TNT) occur once every few thousandyears.
  125. 125. Tunguska Debris The most recent event was in 1908 in Tunguska, Siberia. We are not sure if the object was a meteoroid or a comet, but it exploded in midair with an energy of about 20 to 40 megatons of TNT!We think that asteroid impacts are even more rare. We guessthat they occur once every 600,000 years or so. Such impactswould be large enough to cause global climate changes - a“nuclear winter”.
  126. 126. The leading theory about theextinction of the dinosaurs ofcourse involves an asteroid impact.All over the world you can seeevidence for this in the K-Tboundary in geologic strata(layers).
  127. 127. Jupiter’s Interior The interiors of the Jovian planets are very different from the Terrestrial planets. What we call the “surface” of Jupiter is really the top of the the atmosphere.Just like the Sun, Jupiter is made up of mostly hydrogen andhelium. The colorful clouds in Jupiter’s atmosphere are madeof ammonia, methane, water, and phosphorous and otherchemicals.
  128. 128. Jupiter’s ConvectionJupiter radiates about twice as much heat than it absorbs fromthe Sun. All this energy drives Jupiter’s weather system.The lighter colored zones are regions where warmer materialis rising, and the darker colored belts are regions wherematerial is sinking. All of this convection activity causes manyswirling “storm” systems to be present at any one time inJupiter’s atmosphere
  129. 129. The weather on Jupiter is very dynamic and chaotic. There are many storms or “vortices” like these pictured by the Galileo probe. All Jovian planets have differential rotation - meaning that different regions of the planet rotate at different rates.Galileo mission Nasa/JPL
  130. 130. JupiterMost of what we havelearned about the Jovianplanets has come fromspacecraft.Voyager I and IIGalileo and probeCassini and Huygens
  131. 131. Jupiter’s Storms Galileo mission Nasa/JPL Here you see two picturesThe largest of these storms is taken about 75 min. apart onthe Great Red Spot, first seen the dark side of Jupiter, theby astronomers over 300 years white specks are lightning inago. It is so large the Earth Jupiter’s atmosphere, somecould easily fit inside of it. What 100 to 1000 times brightercauses it and why it is red are than on Earth.still mysteries.
  132. 132. Jupiter’s Interior The “atmosphere” ends about 20,000 km below the surface. The pressure is so great here that hydrogen is forced to become a liquid, and acts like a metal.The very core of Jupiter is probably rocky and metallic, likeEarth, but probably larger and much more dense.
  133. 133. Pioneer 10 Mission All the Jovian planets have extensive magnetic fields Jupiter’s extends well past the orbit of Saturn! Jupiter’s magnetic field is so strong because of the large sea metallic hydrogen that is under the atmosphere. If you could “see” Jupiter’s magnetosphere, from Earth it would look 5 times larger than the full Moon!
  134. 134. Auroras on Jupiter and Saturn Aurorae have been seen on both Jupiter and Saturn.
  135. 135. Saturn Cassini is currently in orbit around Saturn and is continually sending back more data about Saturn and its moons.
  136. 136. Both Jupiter and Saturn rotate in less then 10 hours. This fast rotation rate gives them a squashed look.Saturn is very similar toJupiter in many ways. Their atmospheres aresimilar, with Saturn havingthicker upper level clouds,so less of the more colorfullower clouds can be seen.
  137. 137. Saturn’s Atmosphere Saturn radiates three times as much as it receives from the Sun (unlike Jupiter that radiates only twice as much). We think that this extra heat is coming from the helium in Saturn’s atmosphere condensing and forming “rain”. As this rain falls its energy is turned into heat. This also explains why there is less helium in Saturn’s upper atmosphere compared to Jupiter.
  138. 138. Jovian InteriorsSince Saturn is not quite aslarge as Jupiter, its internalpressures and temperaturesare not as high as those inJupiter, and so its region ofmetallic hydrogen is not asthick.
  139. 139. Saturn’s Weather The weather on Saturn is similar to Jupiter, however there is no “Great Red Spot” like storm on Saturn. NASA/JPL/Space Science Institute
  140. 140. Some storms on Saturn have been seen to rotate “backward” compared to storms on Earth. This has also been seen on Jupiter.NASA/JPL/Space Science Institute
  141. 141. Saturn’s Cloud StructureWe have discovered astrange hexagonstructure around Saturn’snorth pole…. And a“hurricane” with a central“eye” at Saturn’s southpole.
  142. 142. Uranus and NeptuneJust one spacecraft (Voyager II) has visited Uranus andNeptuneBoth planets get their bluish color from methane in theiratmospheres.
  143. 143. Jovian InteriorsWe believe both Uranus and Neptune are just smaller versionsof Jupiter and Saturn on the inside. Neptune emits more heatthan it absorbs (just like Jupiter and Saturn), but Uranus doesnot!
  144. 144. Uranus’s Seasons
  145. 145. Jovian Magnetic FieldsUranus’ and Neptune’s magnetic fields have strangeorientations, and are not at all aligned with the rotation ofthe planet.
  146. 146. Other than the Earth’s Moon, there are only 6 other “major” satellitesin the Solar system: Io, Europa, Ganymede, Callisto, Titan, andTriton. There are many many more satellites, but all of them aresmaller than these. Each of these moons are special and unique in itsown way.
  147. 147. The four moons of Jupiter discoveredby Galileo are called the Galileanmoons. Io orbits the closest toJupiter, followed by Europa,Ganymede, and last Callisto.
  148. 148. Galilean Moon Interiors Io is the most geologically active moon or planet in the Solar System. Tidal forces from Jupiter are constantly deforming the planet. All of the friction deep within the moon causes numerous volcanoes to be active on the surface.We believe that Europa might contain a thick liquid water oceanbeneath a crust of solid ice. The tidal forces on Europa are not as strongas they are of Io, but they are enough to keep its oceans from freezingsolid. Because there is liquid water on the moon, scientists believeEuropa is our best bet of finding life on a world other than our own!
  149. 149. Io
  150. 150. Europa
  151. 151. Galilean Moon Interiors Ganymede is the largest moon in the Solar System, even larger than Mercury or Pluto. Ganymede and Europa both have a magnetic field. We believe Ganymede has a thick water/ice layer around a rocky mantle and an iron core. While we think Callisto is made up of similar material as Ganymede, Callisto is undifferentiated. Basically no geological activity has occured there since it was created some 4.5 billion years ago. This makes it the most heavily cratered object in the Solar System.
  152. 152. Ganymede
  153. 153. Callisto
  154. 154. Titan
  155. 155. Titan’s AtmosphereTitan is the only moon to have a thick atmosphere. Theatmosphere is made up of mostly nitrogen and methane. Themethane on Titan acts very much like water does in the weatherhere on Earth.
  156. 156. Huygens Probe The Huygens probe appears to have seen an ocean and rivers as it descended to the surface of Titan. The surface temperature on Titan is only 94 K (-350 F)! So there is no chance that the ocean and rivers have liquid water, instead they probably have liquid methane. Nasa/JPL/ESAFrom data on how the probe landed,it is believed that the probe landed in“mud” or soft sand.
  157. 157. Enceladus
  158. 158. EnceladusOne of the “minor” moons ofthe Solar System, Enceladus isthe 6th largest moon of Saturn.Cassini has observed a water“plume”. We believe this is a“geyser” formed from a pocketof liquid water under thesurface of the moon.
  159. 159. EnceladusNasa/JPL/ESA
  160. 160. TritonNot a lot is known about Triton. It is the only major moon to orbitits planet backwards. Because of this its orbit is slowly decaying,and someday might form a ring around Neptune! Triton doeshave a thin nitrogen atmosphere, in part due to cryovolcanism.Triton was probably was a Kuiper Belt object that was capturedby Neptune.
  161. 161. Saturn’s RingsOf course the mostamazing thing aboutSaturn is its rings.These rings are madeup millions and millionsof small clumps of ice,most about the size of agolf ball.
  162. 162. This is the Encke gapseen by Cassini right afterorbital insertion aroundSaturn. Cassini wasprobably less than 1000miles from the rings whenthis was taken.NASA/JPL/Space Science Institute
  163. 163. NASA/JPL/Space Science Institute Cassini actually went “through” a gap in the rings during orbital insertion around Saturn. So we were able to get some very close pictures of the rings.
  164. 164. The Rings of Saturn The rings are made up of many many small bands. Several structures can be seen in the rings, gaps, waves, spokesCourtesy NASA/JPL-Caltech NASA/JPL/Space Science Institute
  165. 165. The Rings of Saturn Here “shepherd moons” make rings and gaps.Here different colors represent differentsizes of ice particles. The blue regionshave smaller ice particles
  166. 166. Distortions in the F ring duethe gravity of the moonPrometheus 171
  167. 167. Roche LimitWhen a moon comeswithin a planet’s Rochelimit the tidal forces pullthe moon apart, makingrings!
  168. 168. Just recently Cassini has found larger moonlets in the rings(about 100m by 5000m in size). These could be largerfragments of the larger moon that broke up to form the rings.
  169. 169. Here Cassini is looking directly at the night side of Saturn.You can see the formation of new rings outside the Rochelimit. The outer most ring (the E ring) is formed by the waterplumes from Enceladus.NASA/JPL/Space Science Institute
  170. 170. NASA/JPL/Space ScienceInstitute
  171. 171. Miller-Urey ExperimentThis showed that tocreate the buildingblocks of life you justneed liquid water, basicchemicals, and asource of energy.
  172. 172. Hydrothermal VentsProof that life can exist andflourish without solar energy.
  173. 173. Life on EarthWe think it only took about 50 million years for life to developonce there was a solid surface and oceans on Earth, but for2.5 billion years all life was single celled.Life changed Earth’s early atmosphere, from one with CO 2,N2, methane, and other gasses, to the atmosphere of O 2 andN2 that we have today.Only about half a billion years ago did complex multi-celledlife (plants and animals) evolve.
  174. 174. Life Elsewhere in the Solar SystemPossibly: Europa,MarsLongshot:Ganymede,Enceladus
  175. 175. The Drake EquationThe Drake Equation gives an estimate of the number of otherintelligent civilizations that we can “talk to”. N = R × f p × ne × f l × f i × f t × L R is the rate of star formation (~7 per year) fp is the fraction of stars with planets ne is the number of planets that are habitable fL is the fraction of habitable planets with life fi is the fraction of planets with life that is intelligent ft is the fraction of intelligent life to develop technology L is the lifetime of the technological civilization
  176. 176. The Drake EquationThe Drake Equation gives an estimate of the number of otherintelligent civilizations that we can “talk to”. N = R × f p × ne × f l × f i × f t × LR is the rate of star formation (~7 per year)fp is the fraction of stars with planets (~1??)ne is the number of planets that are habitable (~0.1?)fL is the fraction of habitable planets with life (~1?)fi is the fraction of planets with life that is intelligent (~0.1?)ft is the fraction of intelligent life to develop technology (~0.5?)L is the lifetime of the technological civilization (100,000 years?)These numbers are my guesses.... you can choose your own! 3500 = 7 ×1× 0.1× 1× 0.1× 0.5 × 100000
  177. 177. Drake Equation N = R × f p × ne × f l × f i × f t × L 3500 = 7 ×1× 0.1×1× 0.1× 0.5 ×100000If there are 3500 intelligent civilizations in our galaxy then theaverage distance to the nearest alien civilization is about 160light years!!This means we will probably never have a “conversation” withaliens!Our radio signals have only traveled some 70 light years.
  178. 178. 184
  179. 179. Gliese 581 Gliese 581 is a red dwarf about 20 light years from Earth. Planet “c” around Gliese 581 has a mass of about 5 times greater than Earth’s, and has a radius that could be around 1.5 times larger than Earth’s.This is the first “Earthsized” planet that wehave discoveredaround another star!
  180. 180. Gliese 581 Just this year astronomers announced finding Gliese 581 e with a mass of 1.9 Earth masses. However it orbits very close to the star – it has an orbital period of just over 3 days!Planet “c” has an orbital period of only 13 days and “d” has aperiod of 83 days! It has been calculated that “d” is in thestar’s habitable zone where liquid water could exist on theplanet!
  181. 181. Stellar Habitable Zones
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