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Astronomy 101 The Solar System Tuesday, Wednesday, Thursday Tom Burbine [email protected] ScheduleWhat are meteorites?MeteoriteWhy are meteorites important?Slide 6MoonMeteoritesSlide 9More evidence …Then ..Thomas JeffersonAnd respondedSlide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Falls and FindsFall Statistics (greater than 1%)Where is the best place to find meteorites on Earth?Slide 25Slide 26Antarctic MeteoritesHow do you know a rock is a meteorite?Meteor-wrongsSlide 30Slide 31Basic typesTypes of Stony MeteoritesSlide 34Ordinary ChondritesSlide 36Within each ordinary chondrite groupCarbonaceous ChondritesSlide 39Alteration SequenceCI1 chondriteSlide 42CM2 chondriteCV3 chondriteSlide 45DifferenceOther types of chondritesSlide 48AchondritesDifferentiationEucritesDiogenitesHowarditesAubritesAngritesIronsWidmanstätten patternSlide 58Slide 59AtaxiteOctahedriteHexahedriteStony-IronsPallasiteMesosideritePrimitive AchondritesHow old is the solar system?Slide 68Slide 69AgesHow do you determine this age?Dating a planetary surfaceRadioactivitySlide 74Half-LifeRadioactive DatingSlide 77Slide 78Slide 79Slide 80Slide 81RememberSlide 83Slide 84Slide 85Slide 86What are the assumptions to get an age?What are the assumptions?Basic FormulaSlide 90How do you determine isotopic values?Slide 92It is easierExampleSlide 95Slide 96Slide 97Carbon-14Slide 99Slide 100Slide 101Why is Carbon-14 still present if it has such a short half-life?Slide 103Slide 104What heats the asteroids?Radioactive HeatingTypes of Planetary MissionsMercury/VenusMercuryDifficult to study MercurySlide 111Mariner 10Slide 113Caloris BasinCaloris Basin (Some of the hill are 1,800 meters tall)Slide 116Slide 117Slide 118Slide 119Weird TerrainMercury has high densitySlide 122Slide 123Magnetic FieldMessengerSlide 126Messenger videoSlide 128Slide 129Slide 130Slide 131Spectra of MercuryMercury’s SurfaceSlide 134Slide 135Questions:One possibilityVenusSlide 139Venus’ atmosphereVenus’ cloudsGreenhouse EffectSlide 143Slide 144Runaway Greenhouse EffectSlide 146Slide 147Why does Venus has such a thick atmosphere?SurfaceHow did it do it?Slide 151Slide 152Slide 153Slide 154Maat MonsVolcanoesCratersSlide 158Pancakes DomesCoronaeArachnoidsSlide 162Slide 163VeneraVenera 9Venera 9 and 10 picturesVenera 13Slide 168Slide 169PioneerPioneer 2Pioneer 2 busPioneer 2 Large Probe that entered the atmosphere3 small probesVenus ExpressSlide 176Mostly spare parts from Mars Express or RosettaSlide 178Any Questions?Astronomy 101The Solar SystemTuesday, Wednesday, ThursdayTom [email protected] Schedule•Today – Quiz; Meteorites, Mercury, and Venus•Wednesday - Presentations•Thursday - Mars•Tuesday – Last quiz; Optional final; Final presentationWhat are meteorites?Meteorite•A small extraterrestrial body that reaches the Earth's surfaceWhy are meteorites important?Why are meteorites important?•They are primarily fragments of asteroids, which can hit us•They are records of the early solar systemMoonMeteorites•Usually have ages of ~4.6 billion years•Asteroids and comets are thought to be the building blocks of the terrestrial planetsMeteorites•Many early cultures recognized (or believed) certain stones as having fallen from the sky•Many early cultures had tools made from iron meteorites•But to the scientists of the Renaissance and later periods, stones falling from the heavens were considered superstition or heresyMore evidence …•In 1492, a meteorite weighing almost 130 kilograms landed near the town of Ensisheim, Alsace, France, then in the hands of GermanyThen ..• In 1794, Ernst Friedrich Chladni, considered the father of meteoritics, published a book in which he concluded that stone and iron masses did fall out of the sky•In 1803, thousands of meteorite fragments bombarded L'Aigle in Normandy, France, an event investigated by Jean-Baptiste Biot of the French Academy of Science.Thomas Jefferson•Meteorite landed in Weston, CT•It was brought to Yale where it was concluded it was from outer space•Thomas Jefferson, President of the United states, was told about itAnd responded•"Gentlemen, I would rather believe that two Yankee professors would lie than believe that stones fall from heaven."Meteorites•Named after a nearby geographic localityMeteorite•Esquel Pallasite•Found in Esquel, ArgentinaMeteorites•Almost all are thought to be fragments of asteroids•Where else can they come from?Meteorites•Almost all are thought to be fragments of asteroids•Where else can they come from?–Moon - ~68 samples–Mars - ~34 samples–Comets?–Venus?–Mercury?–Other solar systems?Peekskill Meteorite•http://aquarid.physics.uwo.ca/~pbrown/Videos/peekskill.htmMeteorites•Meteorites are composed of different minerals–Silicates – contain silicon and oxygen–Sulfides – contain sulfur–Oxide – contains oxygen–Iron-nickel metalMeteorites•Usually named after the town (or nearest town) where they fell or were locatedFalls and Finds•Falls – see them fall•Finds – find themFall Statistics (greater than 1%)•Meteorite type Fall Percentages•L chondrites 38.0%•H chondrites 34.1%•LL chondrites 7.9%•Irons 4.2%•Eucrites 2.7%•Howardites 2.1%•CM 1.7%•Diogenites 1.2%•Aubrites 1.0%Where is the best place to find meteorites on Earth?Where is the best place to find meteorites on Earth?•Antarctica•Deserts–SaharaAntarctic Meteorites•Designation for which ice field they were found•ALH Allan HillsEET Elephant MoraineLEW Lewis Cliff•Then year and then number (which gives order of discovery)•For example, ALH 84001 was first meteorite discovered in 1984-1985 field seasonHow do you know a rock is a meteorite?•Some possible indicators•Presence of Iron-Nickel (FeNi) Metal•Density•Magnetism•Presence of Chondrules•Fusion Crust•Regmaglypts–Ablation of meteoritewhile passing throughatmosphereMeteor-wrongs•For example, magnetite (Fe3O4) is magnetic, but has grey streak •The best test is finding Ni in the metallic iron•NWA 736 (H3.7) NWA stands for North West Africa•Hassayampa (H4)•Pultusk (H5)•NWA 869 (L5)•Holbrook (L6)•Long Island (L6)•NWA 2040 (LL3.5)•NWA 1584 (LL5)•NWA 852 (CR2)•NWA 2086 (CV3)•NWA 800 (R4)•NWA 1929 (Howardite)•NWA 3140
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