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Virginia Tech - GEOS 1034 - Class Notes - Week 9

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Virginia Tech - GEOS 1034 - Class Notes - Week 9

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background image Comets: an icy small solar system body that, when close enough to the sun, displays a  visible coma (a thin, fuzzy, temporary atmospheres) and sometimes a tail Mixture of ice and rock that sublimate (solid --> gas) as they approach the sun,  releasing dust and gas to form 2 sails Gas tails are pushed away from the sun by solar winds (charged particles  emitted by the Sun) and are always directed away from the Sun Dust tails are pushed away from the sun by solar radiation (light). Dust particles  slow down with distance from the sun, which causes dust tails to curve Light and fluffy Churyumov-Gerasimenko is the first comet we have orbited with a space craft Rosetta Spacecraft dropped the Philae lander to the surface of C-G which  deployed harpoons to grab it Harpoons didn't work and philae bounced several times before  settling near a cliff § Dust jets from comet tempel 1 contain ejected blocks ranging from 10s of cm Heat of sunrise causes invisible gases to vent but dust jets only occur when  landslides push debris into these gas jets Dust jets don't turn on at sunrise Lose mass with each pass of the sun, will eventually break up once it  approaches the sun Gravity of a comet is several times smaller than Earth's Cannot land a spacecraft on its surface without bouncing off Hubble Space captured Comet LINEAR's breakup Comet ISON Highly elliptical orbit around the sun showed that it came from very far  away We can track the origin of comets by tracking trajectories around the Sun Long-period comets: come from outer solar system, far beyond Pluto, and take  1000s of years to orbit the sun Oort cloud is estimated to have billions of small icy objects as old as the  solar system Long period comets have orbits with an elongated shape, which indicates  they come from an eliptical zone Short-period comets: orbit much closer to the Sun in a matter of decades Captured by gravity of sun Halley's comet: short-period comet that comes into view about once a  lifetime (75 years) Will next appear in 2061 § Only short-period comet that is visible to naked eye § You would not approach a comet through its tail because it ejects blocks the  size of houses Asteroid: a class of small solar system bodies in orbit around the sun the further away  that comets and don't have coma. They can break-up into meteoroids and burn up in 
earth's atmosphere
Made of rock and sometimes metals Large space rocks that range in size from meters to 100s of km They are smooth and with minima flying debris  They reside in the Asteroid belt located between Mars and Jupiter Avg. distance btw them is about 2,000,000 miles Some asteroids orbit inside Mars Asteroids that orbit near earth are called Near Earth Asteroids (NEAs) Estimated 1 million asteroids bigger than 1km in diameter and billions of  smaller ones Meteoroid: small rocks (less than a few meters across) travelling through space Meteors: small rocks from space that light up in the night sky as they burn up the  earth's atmosphere Can be broken up asteroids Perseid meteor shower comes from a partial breakup of Comit Swift-Tuttle Meteorites: small pieces of rock that survive passage through the atmosphere to be  picked up on a planet surface. Exist because meteoroids burn in the Earth's 
atmosphere
Stony meteorites- 93% meteorites are stony Iron meteorites The easiest place to find meteorites is Anartica, where flowing glaciers collect  and deposit them, easily seen against white of Antarctica Martian meteorites: trapped gas bubbles that are identical in composition to  Mars' atmosphere Thought to have been ejected from Mars by large impacts Lafayette meteorite found at Purdue University Impacts: When an asteroid hits earth, it's generally travelling 15 km or 32000 mph which  causes the asteroid to explode like a bomb on impact Resulting crater is 5-30x bigger than impactor Ejecta: rock thrown out of the crater during impact  Mostly lands within 1 diameter of the crater through ejecta rays can  extend 10s of crater diameters` § 3 basic types of craters Simple crater 1km diameter meteor crater in Arizona was caused by an asteroid  only 40 m wide § § Complex crater Complex lunar craters like Tyco (diameter = 86 km) have a central  raised peak and terraced side walls  § Complex Herschel crater on Saturn's icy moon Mimas is the largest  ratio of a crater diameter to the size of the moon or planet anywhere 
in solar system
§ § Multi-ring basin § Impact breccia: angular shattered pieces of rock surrounded by melt from  impact Multi-ring Valhalla basin on Jupiter moon Callisto is the largest impact basin in  the solar system (diameter of outer rings: 3800) Moon Impacts  Very large dark circles on moon are big impact basins filled with lava  (called mare) § Absence of craters in lava shows it's much younger than the rest of  moon's surface § The moon is completely saturated with impact craters, meaning that any  new crater and its ejecta covers older ones § Moon is covered with a layer of ejecta and dust: regolith 10s of meters thick § NASA is concerned about 1st astronauts disappearing in regolith so  they are given big boot pads § § One of Earth's impact craters in Indiana the Kentland Crater Easy to identify because of surface topography § Inside central peak: only place in Indiana where rock layers don't lie  horizontally § Shatter cones found throughout quarry are evidence of passage of high pressure  rock wave If a 500km asteroid hit earth, it would burn Earth out Our moon originated from the impact of a Mars sized planet (Theia) into Earth  4.6 billion years ago An impactor only 10 km in diameter can cause mass extinctions The extinction of dinosaurs was to believe have been caused by a 10km  diameter impactor 65 million years ago Cretaceous (dino ruled) Paleogene (mammal ruled) extinction event  occurred over 65 million years ago killing off 75% species on Earth § Thin layer of clay that separates Cretaceous from Paleogene sediments all  over the world contains a lot of iridium shocked quartz and soot 
indicative of a giant impact and global fire
§ Impact could have killed off dinosaurs and 75% other species in several  ways: Heating of ejecta as it passes through atmosphere cause wildfires § Dust suspended would block sunlight hence global cooling § Ejecta: disrupt ozone layer hence extensive § Sulfate-rich marine rocks in atmosphere would have transformed  into sulfuric acid that rained down on oceans causing them to be 
very acidic
§ § In 1990, the 65 million yr old 180 km diameter Chicxulub crater was identified  buried 1km under sediments off of Mexico's Yucatan Peninsula Revealed by mapping gravity signature and dated from cores drilled  through the sediments § Near Misses of Big Asteroids (1972)- 100m across dipped into Earth's atmosphere, creating a spectacular  fireball, but skipped back in space (1989)- an asteroid 800m in diameter crossed Earth's orbit just 6 hours before  earth would be in that place Mitigating asteroid impacts: Deflection: an impact of an impact spacecraft will result in the impact to change  the orbital velocity  Kinetic impact: crash a heavy spacecraft into it to alter trajectory Spacecraft propulsion: create a small sustained thrust on its side to alter  trajectory Focus solar heat onto a comet surface to create thrust from resulting  vaporization of material Solar sail: attach a large solar sail enabling solar pressure Nuclear weapons Direct hit to vaporize (better not leave big chunks) § Detonate a series of devices close to asteroid § NASA's Deep impact spacecraft smashed into Comet Tempel 1 at 24,000 mph in  order to learn about its structure and chemistry and to demonstrate intercept 
capabilities
Review
What is the main source of wildfires in the US?
People  a. Wind b. Animals scratching on dry vegetation c. 1. Which factors strongly influence wildfires to spread? Strength of wind a. Type of vegetation b. Warm temperatures c. All of above d. 2. What is a surface fire? A fire where surface of trees ignite a. A fire so hot that dirt burns b. A grass/brush fire that burns low to ground c. Fire that is too big to contain d. 3. What is a crown fire? A fire where tops of trees ignite a. A fire where the ground ignites due to dry vegetation b. 4. 3 stages of a wildfire? Drying, heating, wetting a. Pre-heating, detonation, cooling b. Smoking, flaming, glowing c. Pre-ignition, combustion, smouldering d. 5. Which was the largest wildfire in US history? Great fire of 1910 a. Chicago fire b. 6. What was the original policy of the US forest surface? Fight all fires no matter what a. 7. What put out Yellowstone fire 1988? 1/4 inch of snow a. 8. What is current policy of US forest surface? Aggressively fight all wildfires a. Only fight small wildfires b. Don’t fight any wildfires c. Permit wildfires to burn in primitive areas where people and structures are not  in danger d. 9. True or False: Some types of trees require fire to regenerate True a. 10. True or False: Fires are dangerous to preservation of grassland False a. 11. What is the purpose of hotshot crews? To make sure communities comply with fire-prevention rules a. To act as look out and raise an alarm if a wildfire is spotted b. To prevent spread of wildfires c. All of the above d. 12. What is the purpose of an air-tanker? Drops water and fire-retardants on fire a. 13. Why are airtanker flights so dangerous? Fly low a. Fly slow b. Old planes are not designed for this purpose and often used c. All of the above d. 14. What is the advantage that helitankers have over airtankers? Longer range a. Carry more water/fire retardant b. Can refill locally in small bodies of water c. All of the above d. 15. What is the main function of a Smoke jumper? To rescue people a. To catch dangerous criminals that escape from hot shot crews b. To jump over fires c. To get to and fight remote fires before they become too destructive d. 16. Which are fire shelters NOT designed to do? Reflect heat a. Protect against direct sustained contact with flames b. Trap breathable air c. Serve as final effort to survive wildfire d. 17. True or False: A wildfire can burn down a house but leave surrounding lawn  unburned True a. 18. Which is NOT a good wildfire safety practice? Keeping vegetation load within 100 ft of structure a. Using fire-resistant roof shingles b. Parking on dry vegetation c. Soaking a campfire after putting it out  d. 19. What heroic firefighter saved others by forcing them to hide in a mine? Polaski a. 20. What are meteoroids? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 21. What are meteors? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 22. What are meteorites? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 23. Most of asteroids are found where? Between Mars and Jupiter in Asteroid belt a. 24. What are comets? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 25. True or False: We can find Martian meteorites on earth True a. 26. True or False: Asteroid belt is crowded? False a. 27. Why do comets have tails? They have creole volcanoes a. Comets are loose collection of rocks that sun's gravity causes it to spread out b. Solar winds c. Ice in comets turn to gas (sublimates) due to heat from sun and enabling dust  and gas to be released d. 28. Long period comets originate from the oort cloud. Where is the oort cloud? Between Mars and Jupiter a. Around pluto's orbit b. Far beyond pluto's orbit c. Between Jupiter and Neptune d. 29. How do we know the Oort cloud is a sphere? Comets come from all directions a. From eliptical shape of comet's orbit b. We can view from powerful telescopes c. 30. Why is halley's comet the most famous? It's visible a. It comes around every 75 years b. 31. If a 1km asteroid strikes the earth, how big would the crater be? 15-30 km in diameter a. 1km in diameter b. 100 km in diameter c. Asteroid wouldn't cause a crater d. 32. Why are impacts almost always round? Asteroids typically explode on impact creating a shockwave that spreads out  equally in all directions a. Asteroids always hit from nearly straight overhead b. Impact melts rock that spreads equally in all directions c. Collapse of walls of initial crater allows for oval shaped craters to become  rounded d. 33. Why is the surface of some of the largest impact craters black?  Impact happens and lava is developed: called mar a. 34. Why are there more impact craters on moon than on earth? Erosion- moon doesn't have it a. 35. Which is NOT evidence that a large impact killed off dinosaurs? Abundance of iridium found at KT boundary a. Fossilized dinosaurs with severe burns b. Shocked forts evidence at KT boundary c. Discovery of chicxulub crater that is the right size and age d. 36. How many near-earth asteroids greater than or equal to 1km in diameter are currently  being tracked? 1000 a. 10,000 b. 100 c. none d. 37. How often does a 10km asteroid hit the earth? Every hundred million years a. 38. Which is NOT a potential strategy for changing position of asteroid on collision  course with Earth? Detonate nuclear bomb on one side a. Land spacecraft on it to eject material off the surface b. Attach solar sail to the object c. Focus solar heat to create thrust from the resulting sublimation of ice d. 39. Definitions:
Preigntion: 
Oort cloud: Mar: Week 9  Monday, October 22, 2018 12:23 PM
background image Comets: an icy small solar system body that, when close enough to the sun, displays a  visible coma (a thin, fuzzy, temporary atmospheres) and sometimes a tail Mixture of ice and rock that sublimate (solid --> gas) as they approach the sun,  releasing dust and gas to form 2 sails Gas tails are pushed away from the sun by solar winds (charged particles  emitted by the Sun) and are always directed away from the Sun Dust tails are pushed away from the sun by solar radiation (light). Dust particles  slow down with distance from the sun, which causes dust tails to curve Light and fluffy Churyumov-Gerasimenko is the first comet we have orbited with a space craft Rosetta Spacecraft dropped the Philae lander to the surface of C-G which  deployed harpoons to grab it Harpoons didn't work and philae bounced several times before  settling near a cliff § Dust jets from comet tempel 1 contain ejected blocks ranging from 10s of cm Heat of sunrise causes invisible gases to vent but dust jets only occur when  landslides push debris into these gas jets Dust jets don't turn on at sunrise Lose mass with each pass of the sun, will eventually break up once it  approaches the sun Gravity of a comet is several times smaller than Earth's Cannot land a spacecraft on its surface without bouncing off Hubble Space captured Comet LINEAR's breakup Comet ISON Highly elliptical orbit around the sun showed that it came from very far  away We can track the origin of comets by tracking trajectories around the Sun Long-period comets: come from outer solar system, far beyond Pluto, and take  1000s of years to orbit the sun Oort cloud is estimated to have billions of small icy objects as old as the  solar system Long period comets have orbits with an elongated shape, which indicates  they come from an eliptical zone Short-period comets: orbit much closer to the Sun in a matter of decades Captured by gravity of sun Halley's comet: short-period comet that comes into view about once a  lifetime (75 years) Will next appear in 2061 § Only short-period comet that is visible to naked eye § You would not approach a comet through its tail because it ejects blocks the  size of houses Asteroid: a class of small solar system bodies in orbit around the sun the further away  that comets and don't have coma. They can break-up into meteoroids and burn up in 
earth's atmosphere
Made of rock and sometimes metals Large space rocks that range in size from meters to 100s of km They are smooth and with minima flying debris  They reside in the Asteroid belt located between Mars and Jupiter Avg. distance btw them is about 2,000,000 miles Some asteroids orbit inside Mars Asteroids that orbit near earth are called Near Earth Asteroids (NEAs) Estimated 1 million asteroids bigger than 1km in diameter and billions of  smaller ones Meteoroid: small rocks (less than a few meters across) travelling through space Meteors: small rocks from space that light up in the night sky as they burn up the  earth's atmosphere Can be broken up asteroids Perseid meteor shower comes from a partial breakup of Comit Swift-Tuttle Meteorites: small pieces of rock that survive passage through the atmosphere to be  picked up on a planet surface. Exist because meteoroids burn in the Earth's 
atmosphere
Stony meteorites- 93% meteorites are stony Iron meteorites The easiest place to find meteorites is Anartica, where flowing glaciers collect  and deposit them, easily seen against white of Antarctica Martian meteorites: trapped gas bubbles that are identical in composition to  Mars' atmosphere Thought to have been ejected from Mars by large impacts Lafayette meteorite found at Purdue University Impacts: When an asteroid hits earth, it's generally travelling 15 km or 32000 mph which  causes the asteroid to explode like a bomb on impact Resulting crater is 5-30x bigger than impactor Ejecta: rock thrown out of the crater during impact  Mostly lands within 1 diameter of the crater through ejecta rays can  extend 10s of crater diameters` § 3 basic types of craters Simple crater 1km diameter meteor crater in Arizona was caused by an asteroid  only 40 m wide § § Complex crater Complex lunar craters like Tyco (diameter = 86 km) have a central  raised peak and terraced side walls  § Complex Herschel crater on Saturn's icy moon Mimas is the largest  ratio of a crater diameter to the size of the moon or planet anywhere 
in solar system
§ § Multi-ring basin § Impact breccia: angular shattered pieces of rock surrounded by melt from  impact Multi-ring Valhalla basin on Jupiter moon Callisto is the largest impact basin in  the solar system (diameter of outer rings: 3800) Moon Impacts  Very large dark circles on moon are big impact basins filled with lava  (called mare) § Absence of craters in lava shows it's much younger than the rest of  moon's surface § The moon is completely saturated with impact craters, meaning that any  new crater and its ejecta covers older ones § Moon is covered with a layer of ejecta and dust: regolith 10s of meters thick § NASA is concerned about 1st astronauts disappearing in regolith so  they are given big boot pads § § One of Earth's impact craters in Indiana the Kentland Crater Easy to identify because of surface topography § Inside central peak: only place in Indiana where rock layers don't lie  horizontally § Shatter cones found throughout quarry are evidence of passage of high pressure  rock wave If a 500km asteroid hit earth, it would burn Earth out Our moon originated from the impact of a Mars sized planet (Theia) into Earth  4.6 billion years ago An impactor only 10 km in diameter can cause mass extinctions The extinction of dinosaurs was to believe have been caused by a 10km  diameter impactor 65 million years ago Cretaceous (dino ruled) Paleogene (mammal ruled) extinction event  occurred over 65 million years ago killing off 75% species on Earth § Thin layer of clay that separates Cretaceous from Paleogene sediments all  over the world contains a lot of iridium shocked quartz and soot 
indicative of a giant impact and global fire
§ Impact could have killed off dinosaurs and 75% other species in several  ways: Heating of ejecta as it passes through atmosphere cause wildfires § Dust suspended would block sunlight hence global cooling § Ejecta: disrupt ozone layer hence extensive § Sulfate-rich marine rocks in atmosphere would have transformed  into sulfuric acid that rained down on oceans causing them to be 
very acidic
§ § In 1990, the 65 million yr old 180 km diameter Chicxulub crater was identified  buried 1km under sediments off of Mexico's Yucatan Peninsula Revealed by mapping gravity signature and dated from cores drilled  through the sediments § Near Misses of Big Asteroids (1972)- 100m across dipped into Earth's atmosphere, creating a spectacular  fireball, but skipped back in space (1989)- an asteroid 800m in diameter crossed Earth's orbit just 6 hours before  earth would be in that place Mitigating asteroid impacts: Deflection: an impact of an impact spacecraft will result in the impact to change  the orbital velocity  Kinetic impact: crash a heavy spacecraft into it to alter trajectory Spacecraft propulsion: create a small sustained thrust on its side to alter  trajectory Focus solar heat onto a comet surface to create thrust from resulting  vaporization of material Solar sail: attach a large solar sail enabling solar pressure Nuclear weapons Direct hit to vaporize (better not leave big chunks) § Detonate a series of devices close to asteroid § NASA's Deep impact spacecraft smashed into Comet Tempel 1 at 24,000 mph in  order to learn about its structure and chemistry and to demonstrate intercept 
capabilities
Review
What is the main source of wildfires in the US?
People  a. Wind b. Animals scratching on dry vegetation c. 1. Which factors strongly influence wildfires to spread? Strength of wind a. Type of vegetation b. Warm temperatures c. All of above d. 2. What is a surface fire? A fire where surface of trees ignite a. A fire so hot that dirt burns b. A grass/brush fire that burns low to ground c. Fire that is too big to contain d. 3. What is a crown fire? A fire where tops of trees ignite a. A fire where the ground ignites due to dry vegetation b. 4. 3 stages of a wildfire? Drying, heating, wetting a. Pre-heating, detonation, cooling b. Smoking, flaming, glowing c. Pre-ignition, combustion, smouldering d. 5. Which was the largest wildfire in US history? Great fire of 1910 a. Chicago fire b. 6. What was the original policy of the US forest surface? Fight all fires no matter what a. 7. What put out Yellowstone fire 1988? 1/4 inch of snow a. 8. What is current policy of US forest surface? Aggressively fight all wildfires a. Only fight small wildfires b. Don’t fight any wildfires c. Permit wildfires to burn in primitive areas where people and structures are not  in danger d. 9. True or False: Some types of trees require fire to regenerate True a. 10. True or False: Fires are dangerous to preservation of grassland False a. 11. What is the purpose of hotshot crews? To make sure communities comply with fire-prevention rules a. To act as look out and raise an alarm if a wildfire is spotted b. To prevent spread of wildfires c. All of the above d. 12. What is the purpose of an air-tanker? Drops water and fire-retardants on fire a. 13. Why are airtanker flights so dangerous? Fly low a. Fly slow b. Old planes are not designed for this purpose and often used c. All of the above d. 14. What is the advantage that helitankers have over airtankers? Longer range a. Carry more water/fire retardant b. Can refill locally in small bodies of water c. All of the above d. 15. What is the main function of a Smoke jumper? To rescue people a. To catch dangerous criminals that escape from hot shot crews b. To jump over fires c. To get to and fight remote fires before they become too destructive d. 16. Which are fire shelters NOT designed to do? Reflect heat a. Protect against direct sustained contact with flames b. Trap breathable air c. Serve as final effort to survive wildfire d. 17. True or False: A wildfire can burn down a house but leave surrounding lawn  unburned True a. 18. Which is NOT a good wildfire safety practice? Keeping vegetation load within 100 ft of structure a. Using fire-resistant roof shingles b. Parking on dry vegetation c. Soaking a campfire after putting it out  d. 19. What heroic firefighter saved others by forcing them to hide in a mine? Polaski a. 20. What are meteoroids? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 21. What are meteors? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 22. What are meteorites? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 23. Most of asteroids are found where? Between Mars and Jupiter in Asteroid belt a. 24. What are comets? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 25. True or False: We can find Martian meteorites on earth True a. 26. True or False: Asteroid belt is crowded? False a. 27. Why do comets have tails? They have creole volcanoes a. Comets are loose collection of rocks that sun's gravity causes it to spread out b. Solar winds c. Ice in comets turn to gas (sublimates) due to heat from sun and enabling dust  and gas to be released d. 28. Long period comets originate from the oort cloud. Where is the oort cloud? Between Mars and Jupiter a. Around pluto's orbit b. Far beyond pluto's orbit c. Between Jupiter and Neptune d. 29. How do we know the Oort cloud is a sphere? Comets come from all directions a. From eliptical shape of comet's orbit b. We can view from powerful telescopes c. 30. Why is halley's comet the most famous? It's visible a. It comes around every 75 years b. 31. If a 1km asteroid strikes the earth, how big would the crater be? 15-30 km in diameter a. 1km in diameter b. 100 km in diameter c. Asteroid wouldn't cause a crater d. 32. Why are impacts almost always round? Asteroids typically explode on impact creating a shockwave that spreads out  equally in all directions a. Asteroids always hit from nearly straight overhead b. Impact melts rock that spreads equally in all directions c. Collapse of walls of initial crater allows for oval shaped craters to become  rounded d. 33. Why is the surface of some of the largest impact craters black?  Impact happens and lava is developed: called mar a. 34. Why are there more impact craters on moon than on earth? Erosion- moon doesn't have it a. 35. Which is NOT evidence that a large impact killed off dinosaurs? Abundance of iridium found at KT boundary a. Fossilized dinosaurs with severe burns b. Shocked forts evidence at KT boundary c. Discovery of chicxulub crater that is the right size and age d. 36. How many near-earth asteroids greater than or equal to 1km in diameter are currently  being tracked? 1000 a. 10,000 b. 100 c. none d. 37. How often does a 10km asteroid hit the earth? Every hundred million years a. 38. Which is NOT a potential strategy for changing position of asteroid on collision  course with Earth? Detonate nuclear bomb on one side a. Land spacecraft on it to eject material off the surface b. Attach solar sail to the object c. Focus solar heat to create thrust from the resulting sublimation of ice d. 39. Definitions:
Preigntion: 
Oort cloud: Mar: Week 9  Monday, October 22, 2018 12:23 PM
background image Comets: an icy small solar system body that, when close enough to the sun, displays a  visible coma (a thin, fuzzy, temporary atmospheres) and sometimes a tail Mixture of ice and rock that sublimate (solid --> gas) as they approach the sun,  releasing dust and gas to form 2 sails Gas tails are pushed away from the sun by solar winds (charged particles  emitted by the Sun) and are always directed away from the Sun Dust tails are pushed away from the sun by solar radiation (light). Dust particles  slow down with distance from the sun, which causes dust tails to curve Light and fluffy Churyumov-Gerasimenko is the first comet we have orbited with a space craft Rosetta Spacecraft dropped the Philae lander to the surface of C-G which  deployed harpoons to grab it Harpoons didn't work and philae bounced several times before  settling near a cliff § Dust jets from comet tempel 1 contain ejected blocks ranging from 10s of cm Heat of sunrise causes invisible gases to vent but dust jets only occur when  landslides push debris into these gas jets Dust jets don't turn on at sunrise Lose mass with each pass of the sun, will eventually break up once it  approaches the sun Gravity of a comet is several times smaller than Earth's Cannot land a spacecraft on its surface without bouncing off Hubble Space captured Comet LINEAR's breakup Comet ISON Highly elliptical orbit around the sun showed that it came from very far  away We can track the origin of comets by tracking trajectories around the Sun Long-period comets: come from outer solar system, far beyond Pluto, and take  1000s of years to orbit the sun Oort cloud is estimated to have billions of small icy objects as old as the  solar system Long period comets have orbits with an elongated shape, which indicates  they come from an eliptical zone Short-period comets: orbit much closer to the Sun in a matter of decades Captured by gravity of sun Halley's comet: short-period comet that comes into view about once a  lifetime (75 years) Will next appear in 2061 § Only short-period comet that is visible to naked eye § You would not approach a comet through its tail because it ejects blocks the  size of houses Asteroid: a class of small solar system bodies in orbit around the sun the further away  that comets and don't have coma. They can break-up into meteoroids and burn up in 
earth's atmosphere
Made of rock and sometimes metals Large space rocks that range in size from meters to 100s of km They are smooth and with minima flying debris  They reside in the Asteroid belt located between Mars and Jupiter Avg. distance btw them is about 2,000,000 miles Some asteroids orbit inside Mars Asteroids that orbit near earth are called Near Earth Asteroids (NEAs) Estimated 1 million asteroids bigger than 1km in diameter and billions of  smaller ones Meteoroid: small rocks (less than a few meters across) travelling through space Meteors: small rocks from space that light up in the night sky as they burn up the  earth's atmosphere Can be broken up asteroids Perseid meteor shower comes from a partial breakup of Comit Swift-Tuttle Meteorites: small pieces of rock that survive passage through the atmosphere to be  picked up on a planet surface. Exist because meteoroids burn in the Earth's 
atmosphere
Stony meteorites- 93% meteorites are stony Iron meteorites The easiest place to find meteorites is Anartica, where flowing glaciers collect  and deposit them, easily seen against white of Antarctica Martian meteorites: trapped gas bubbles that are identical in composition to  Mars' atmosphere Thought to have been ejected from Mars by large impacts Lafayette meteorite found at Purdue University Impacts: When an asteroid hits earth, it's generally travelling 15 km or 32000 mph which  causes the asteroid to explode like a bomb on impact Resulting crater is 5-30x bigger than impactor Ejecta: rock thrown out of the crater during impact  Mostly lands within 1 diameter of the crater through ejecta rays can  extend 10s of crater diameters` § 3 basic types of craters Simple crater 1km diameter meteor crater in Arizona was caused by an asteroid  only 40 m wide § § Complex crater Complex lunar craters like Tyco (diameter = 86 km) have a central  raised peak and terraced side walls  § Complex Herschel crater on Saturn's icy moon Mimas is the largest  ratio of a crater diameter to the size of the moon or planet anywhere 
in solar system
§ § Multi-ring basin § Impact breccia: angular shattered pieces of rock surrounded by melt from  impact Multi-ring Valhalla basin on Jupiter moon Callisto is the largest impact basin in  the solar system (diameter of outer rings: 3800) Moon Impacts  Very large dark circles on moon are big impact basins filled with lava  (called mare) § Absence of craters in lava shows it's much younger than the rest of  moon's surface § The moon is completely saturated with impact craters, meaning that any  new crater and its ejecta covers older ones § Moon is covered with a layer of ejecta and dust: regolith 10s of meters thick § NASA is concerned about 1st astronauts disappearing in regolith so  they are given big boot pads § § One of Earth's impact craters in Indiana the Kentland Crater Easy to identify because of surface topography § Inside central peak: only place in Indiana where rock layers don't lie  horizontally § Shatter cones found throughout quarry are evidence of passage of high pressure  rock wave If a 500km asteroid hit earth, it would burn Earth out Our moon originated from the impact of a Mars sized planet (Theia) into Earth  4.6 billion years ago An impactor only 10 km in diameter can cause mass extinctions The extinction of dinosaurs was to believe have been caused by a 10km  diameter impactor 65 million years ago Cretaceous (dino ruled) Paleogene (mammal ruled) extinction event  occurred over 65 million years ago killing off 75% species on Earth § Thin layer of clay that separates Cretaceous from Paleogene sediments all  over the world contains a lot of iridium shocked quartz and soot 
indicative of a giant impact and global fire
§ Impact could have killed off dinosaurs and 75% other species in several  ways: Heating of ejecta as it passes through atmosphere cause wildfires § Dust suspended would block sunlight hence global cooling § Ejecta: disrupt ozone layer hence extensive § Sulfate-rich marine rocks in atmosphere would have transformed  into sulfuric acid that rained down on oceans causing them to be 
very acidic
§ § In 1990, the 65 million yr old 180 km diameter Chicxulub crater was identified  buried 1km under sediments off of Mexico's Yucatan Peninsula Revealed by mapping gravity signature and dated from cores drilled  through the sediments § Near Misses of Big Asteroids (1972)- 100m across dipped into Earth's atmosphere, creating a spectacular  fireball, but skipped back in space (1989)- an asteroid 800m in diameter crossed Earth's orbit just 6 hours before  earth would be in that place Mitigating asteroid impacts: Deflection: an impact of an impact spacecraft will result in the impact to change  the orbital velocity  Kinetic impact: crash a heavy spacecraft into it to alter trajectory Spacecraft propulsion: create a small sustained thrust on its side to alter  trajectory Focus solar heat onto a comet surface to create thrust from resulting  vaporization of material Solar sail: attach a large solar sail enabling solar pressure Nuclear weapons Direct hit to vaporize (better not leave big chunks) § Detonate a series of devices close to asteroid § NASA's Deep impact spacecraft smashed into Comet Tempel 1 at 24,000 mph in  order to learn about its structure and chemistry and to demonstrate intercept 
capabilities
Review
What is the main source of wildfires in the US?
People  a. Wind b. Animals scratching on dry vegetation c. 1. Which factors strongly influence wildfires to spread? Strength of wind a. Type of vegetation b. Warm temperatures c. All of above d. 2. What is a surface fire? A fire where surface of trees ignite a. A fire so hot that dirt burns b. A grass/brush fire that burns low to ground c. Fire that is too big to contain d. 3. What is a crown fire? A fire where tops of trees ignite a. A fire where the ground ignites due to dry vegetation b. 4. 3 stages of a wildfire? Drying, heating, wetting a. Pre-heating, detonation, cooling b. Smoking, flaming, glowing c. Pre-ignition, combustion, smouldering d. 5. Which was the largest wildfire in US history? Great fire of 1910 a. Chicago fire b. 6. What was the original policy of the US forest surface? Fight all fires no matter what a. 7. What put out Yellowstone fire 1988? 1/4 inch of snow a. 8. What is current policy of US forest surface? Aggressively fight all wildfires a. Only fight small wildfires b. Don’t fight any wildfires c. Permit wildfires to burn in primitive areas where people and structures are not  in danger d. 9. True or False: Some types of trees require fire to regenerate True a. 10. True or False: Fires are dangerous to preservation of grassland False a. 11. What is the purpose of hotshot crews? To make sure communities comply with fire-prevention rules a. To act as look out and raise an alarm if a wildfire is spotted b. To prevent spread of wildfires c. All of the above d. 12. What is the purpose of an air-tanker? Drops water and fire-retardants on fire a. 13. Why are airtanker flights so dangerous? Fly low a. Fly slow b. Old planes are not designed for this purpose and often used c. All of the above d. 14. What is the advantage that helitankers have over airtankers? Longer range a. Carry more water/fire retardant b. Can refill locally in small bodies of water c. All of the above d. 15. What is the main function of a Smoke jumper? To rescue people a. To catch dangerous criminals that escape from hot shot crews b. To jump over fires c. To get to and fight remote fires before they become too destructive d. 16. Which are fire shelters NOT designed to do? Reflect heat a. Protect against direct sustained contact with flames b. Trap breathable air c. Serve as final effort to survive wildfire d. 17. True or False: A wildfire can burn down a house but leave surrounding lawn  unburned True a. 18. Which is NOT a good wildfire safety practice? Keeping vegetation load within 100 ft of structure a. Using fire-resistant roof shingles b. Parking on dry vegetation c. Soaking a campfire after putting it out  d. 19. What heroic firefighter saved others by forcing them to hide in a mine? Polaski a. 20. What are meteoroids? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 21. What are meteors? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 22. What are meteorites? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 23. Most of asteroids are found where? Between Mars and Jupiter in Asteroid belt a. 24. What are comets? Large rocks that are meters to hundreds of km in size that orbit the Sun  primarily btw Mars and Jupiter a. Small pieces of space rock that survive the passage of atmosphere to be picked  up on the planet's surface b. Small rocks from space that light up night sky as they burn up in earth's  atmosphere c. Only a few meters across and travel through space d. Dirty iceballs: a mixture of ice and rock that come form far out in the solar  system and form tails of dust and gas as they approach the Sun e. 25. True or False: We can find Martian meteorites on earth True a. 26. True or False: Asteroid belt is crowded? False a. 27. Why do comets have tails? They have creole volcanoes a. Comets are loose collection of rocks that sun's gravity causes it to spread out b. Solar winds c. Ice in comets turn to gas (sublimates) due to heat from sun and enabling dust  and gas to be released d. 28. Long period comets originate from the oort cloud. Where is the oort cloud? Between Mars and Jupiter a. Around pluto's orbit b. Far beyond pluto's orbit c. Between Jupiter and Neptune d. 29. How do we know the Oort cloud is a sphere? Comets come from all directions a. From eliptical shape of comet's orbit b. We can view from powerful telescopes c. 30. Why is halley's comet the most famous? It's visible a. It comes around every 75 years b. 31. If a 1km asteroid strikes the earth, how big would the crater be? 15-30 km in diameter a. 1km in diameter b. 100 km in diameter c. Asteroid wouldn't cause a crater d. 32. Why are impacts almost always round? Asteroids typically explode on impact creating a shockwave that spreads out  equally in all directions a. Asteroids always hit from nearly straight overhead b. Impact melts rock that spreads equally in all directions c. Collapse of walls of initial crater allows for oval shaped craters to become  rounded d. 33. Why is the surface of some of the largest impact craters black?  Impact happens and lava is developed: called mar a. 34. Why are there more impact craters on moon than on earth? Erosion- moon doesn't have it a. 35. Which is NOT evidence that a large impact killed off dinosaurs? Abundance of iridium found at KT boundary a. Fossilized dinosaurs with severe burns b. Shocked forts evidence at KT boundary c. Discovery of chicxulub crater that is the right size and age d. 36. How many near-earth asteroids greater than or equal to 1km in diameter are currently  being tracked? 1000 a. 10,000 b. 100 c. none d. 37. How often does a 10km asteroid hit the earth? Every hundred million years a. 38. Which is NOT a potential strategy for changing position of asteroid on collision  course with Earth? Detonate nuclear bomb on one side a. Land spacecraft on it to eject material off the surface b. Attach solar sail to the object c. Focus solar heat to create thrust from the resulting sublimation of ice d. 39. Definitions:
Preigntion: 
Oort cloud: Mar: Week 9  Monday, October 22, 2018 12:23 PM

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School: Virginia Polytechnic Institute and State University
Department: Geoscience
Course: Geoscience
Professor: Ying Zhou
Term: Fall 2018
Tags:
Name: Week 9 Notes
Description: These notes cover comets, meteoroids, and asteroids
Uploaded: 11/04/2018
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