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Remnants of Rock and Ice • Asteroids • Meteoroids (meteorites, meteor) • Comets Remnants of the Solar Nebula •Small bodies remain virtually _________ unchanged since their formation _________ 4.5 billion years ago •They carry history of the Solar system in their compositions ___________, ________, and _______. numbers Asteroid means ________, starlike a rocky leftover Meteoroid – small rocky material in space _____ in the atmosphere (falling star) Meteor – ________________ Meteorite – any piece of rock than fell to the ______ ground from the sky Comet means _____ hair (Greek), an icy leftover Asteroids (minor planets) • Most abundant _______ between the orbits of Mars and Jupiter • Largest is ______, Ceres 800 km diameter • Most are much Smaller, irregular _______________ Ceres Asteroid Eros Asteroids (minor planets) Evolution of the Belt Early in the history of the Solar system, the belt contained enough planetesimals to form a planet. Gravitational tugs from _______ Jupiter created the gaps. Two stable zones along Jupiter’s orbit host two families of asteroids (_______). Trojans Jupiter’s Trojan Asteroids Meteorites rock that fell Meteorites are pieces of _____ from the sky. fireballs (sometimes with sound) Seen as _______ May cause damage, but most fall into oceans ______ Earth Pelted with Ashes from Nearby Supernova Explosions Meteorites Meteor showers – result of the Earth’s ________________________ passing through a comet orbit Meteors are ___________ single pieces of comet dust ___________ 25 million meteoroids enter Earth’s atmosphere every day Meteor showers get their names after ______________ constellations from which they appear to radiate Meteor Showers (These occur when earth passes through cloud of debris along a comet’s orbit.) Ionized Trail Generation by Meteor Crossing Eastern US, 1992 The Origin of Meteorites ________ Primitive meteorites may be either rocky or carbon-rich ___________ Processed meteorites can be removed from the surface of a planet by an impact. There are meteorites from Moon and Mars found on Earth. shootingstar_. wmv http://www.youtube.com/watch?v=cajfFtu_ QPA&feature=related http://www.youtube.com/watch?v=dpmXyJr s7iU https://www.youtube.com/watch?feature= player_embedded&v=OFDrHe7IzA8 November 2nd, 2015 https://www.youtube.com/watch?v=7dCT407AM NE November 4th, 2015 http://www.msn.com/enus/video/downtime/extremely-closemeteor-strike-caught-on-film/vi-BBpG13b Feb. 18, 2016 Primitive Meteorites Processed Meteorites Giant meteor hits Earth. Why no one saw it. The largest meteor since the 2013 impact in Chelyabinsk, Russia, hit Earth on Feb. 6, 2016. The fireball fell into the ocean off the coast of Brazil and released energy roughly equivalent to 13,000 tons of TNT. This is significantly less than the Chelyabinsk impact, with the equivalent of 500,000 tons of TNT, but it was at least 26 times as powerful as any of the three impacts NASA reported in February 2015. rock and • Chunks of ________ ___ ice in highly eccentric orbits • Near sun, ice sublimates to __________ “tail” produce _____ • A couple have been visited by robotic craft Comets Comet Structure Comets are basically _____________ dirty snowballs where ice mixes with rocky dust. Their mean size is a __________________. few kilometers across The comet body is called _______. nucleus coma Sublimating ices create _____. A tail pointing _____ away from the Sun appears. There are two ___ tails: plasma tail and dust tail. Comets Comet Orbits Comets Comets contain information about the _____ outer solar system Most of them visit the inner part only once, a few are regular guests One of the most famous comets is _______ Halley’s _____. comet It was discovered by Edmund Halley in 1682. Its orbital period is 76 years. The last appearance in 1986. (2062) Halley’s Comet Comet Hale-Bopp Comet ShoemakerShoemaker-Levy 9 Comet ISON Scott Ferguson captured this image of Comet ISON on Oct. 27 while at a friend's private observatory, Northwest Florida Observatory. • Discovered in September 2012 by two Russian amateur astronomers • Thought to be making its maiden voyage to the inner solar system from the Oort Cloud. • ISON made its closest approach to the Sun on Nov. 28, 2013 when it came within a mere 730,000 miles (1.2 million kilometers) of the solar surface. • ISON broke up after passing the Sun and was relatively underwhelming. Comet 67P/ Churyumov-Gerasimenko • A European robot probe Philea, released from the Rosetta spacecraft, has made the first, historic landing on a comet. Philae's landing site is on the head of the 4km-wide rubberduckshaped comet Leg of Lander Nucleus Photo from Philae shows the surface during the lander's approach Earth impacts • Do we ever get hit? • Yes! The questions are when and by what? size • Classify events by ____ –Small –Medium –Large Impacts The ______ larger the ________, impactor the _________ more rare the impact In 1908, an unusual explosion occurred in Siberia ________. Arizona formed 50,000 Meteor crater in _______ years ago. A ____________ larger impactor occurred ___ 65 million years ago perhaps caused the _________________. dinosaur extinction Earth impacts: small • Small: _____ less than ___________ 50 m across at top of atmosphere all the time – Happening _____________ – Will burn up or break up in the atmosphere _________ – Most are very tiny (‘pea’ sized) Shooting stars – Meteors! (“_____________”, “Falling stars”) • Can see 3 - 5 per hour on a typical night • 25 million every day! • 100 tons per day © AP Photo: Yekaterina Pustynnikova, Chelyabinsk.ru http://abclocal.go.com/wls/story?id=8997035 •This meteoroid was only 62 feet wide. •Traveling at 42,000 mph. • Burst over Chelyabinsk in February with the force of 40 Hiroshima-type atom bombs. •It released a shock wave that shattered thousands of windows and injured more than 1,600 people. •Its flash was bright enough to temporarily blind 70 people and cause dozens of skinpeeling sunburns just after dawn in icy Russia. http://www.redorbit.com/news/video/space_2/1112977820/russianmeteorite-fragment-ural-mountains-lakebed-101713/ Earth impacts: medium • Medium: ________________ 50 m – 1 km across at top of atmosphere –Only ~ __________________ one every century or millennium ____________ –Causes “severe local damage” –Two great examples from ‘recent’ history Earth impacts: medium • The Tunguska event - Siberia, Russia –Happened in 1908 Flattened a forest –_________ –Knocked people over _______ 200 km (140 miles) away No crater (exploded just above –__________ ground) • The impactor? –A stony meteorite (?) Size: 30 m The Tunguska event The Tunguska event Earth impacts: medium • The Berringer Crater, in Arizona –Happened ______________ 50,000 years ago –The crater: • _____ 1,200 m across 200 m deep • ____ Earth impacts: medium • The impactor? –An iron meteorite 100 m across (50 m on impact) –____________ –Going _______ 40,000 mph! –Explosion = ____________ 20 million tons of TNT • A moderate atomic bomb • 2 Mt. Saint Helens The Berringer crater, Arizona Earth impacts: large • Large: ___________________ more than 1 km across at top of atmosphere One every ________________ –____ few million years –Severe global effects –More than __ 2 km can cause mass extinction –Most recent: 65 million years ago Earth impacts: large • The K/T extinction event –Some history… • ‘K/T’ = ‘Cretaceous / Tertiary’ • 60 % of all species on Earth disappeared, including the dinosaurs • One explanation (there are several): Earth was hit by a large impactor Earth impacts: large • The K/T extinction event –Evidence for an impact: Iridium found at that • _______ geologic level • A crater near the _________, Yucatan in Mexico The K/T extinction event Earth impacts: large • The K/T extinction event –The impactor: Asteroid • Probably an ________ • Size: ~ ___________ 10 km across • Energy released: 100 million million tons of TNT –____ –__ 5 million atomic bombs 10 million Mt. Saint Helens –___ How often is there an impacted? How often do impacts occur? How To Avoid Impacts? Bombs - Detonate close - push object away Lasers - Pulses to decrease mass, slows Solar collectors -Vaporize to decrease mass Kinetic kill – Space speed bumps - slows Dock & push – Space craft pushes object Solar sails – Use solar wind to push object Gravity tractor – position craft close http://astro1.panet.utoledo.edu/~anatoly/astr1010/materials/324,41,Slide 41 http://campus.pari.edu/sara/arecibo/presentations/fields/294,13,Meteor Trail Recorded During Leonid Meteor Shower, 1998 http://departments.weber.edu/physics/schroeder/astro/lectureslides/356,8,Kuiper Belt objects (other stuff near Pluto) http://www.phys-astro.sonoma.edu/people/faculty/carico/A100/367,2,Earth impacts