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EOSC 114 > Impacts 4 > Flashcards

Impacts 4 Flashcards

1
Q

Meteoroids

A
  • small rocks (< 1m)
  • from asteroid belt
  • Meteors as enter Earth’s atmos
  • Meteorite if survives entry as intact rock and hits earth
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2
Q

Bolides

A

a type of Meteoroid, fireballs that explode in the atmosphere

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3
Q

Asteroids

A
  • large rocks (> 1m)
  • smaller than a planet
  • from asteroid belt
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4
Q

Comets

A
  • Rock with ice
  • leftovers from planet formation
  • near sun, has a tail of gas/dust particles
  • from Kuiper Belt or Oort Cloud
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5
Q

Why do impact craters appear rare on Earth compared to the moon?

A
  • The moon protects the Earth by blocking many incoming asteroids and comets
  • rain/wind/ice erodes the craters on Earth
  • Plate tectonics and volcanism remove evidence of craters
  • Earth’s atmosphere shields cuz most impactors burn up before impact

moon has larger surface area but that doesn’t rlly mean more meteors will hit

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6
Q

Describe the raup and sepkoski hypothesis

A

1984
- suggested there might be ~25 Myr cycle in impacts and extinctions
- due to gravitational disruption of the Oort Cloud caused by…

  1. Nemesis
  2. Planet 9
  3. Moving through Galactic Plane
  4. Coincidence?

-> NASA thinks there is no cyclicality in past extinctions

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7
Q

List and describe some recent impacts and near misses

A
  1. Tunguska Russia - 1908 June 30
  2. Chelyabinsk Russia - 2013 Feb 15
  3. Asteroid 2019OK - 2019 July 25
  4. Asteroid 2005YU55 - 2011 Nov 8
  5. Eastern Mediterranean Event - 2002 June 6
  6. Asteroid 99942 Apophis
    - will approach Earth on April 13, 2019
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8
Q

Briefly describe what is being done right now (impacts)

A
  1. Torino Scale
    - 5 and above is threatening
  2. Spaceguard Survey
    - tracks large objects near earth
  3. NEO Surveyor spacecraft to be launched 2026
    - infrared telescope to survey for danger rocks
  4. Double Asteroid Redirection Test - 2022
    - an impactor crashed into Dimorphos and altered the orbit by a little
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9
Q

List possible mitigation strategies

A
  1. Fragmentation
  2. Rapid Orbit Adjustment
  3. Gradual Orbit Adjustment
  4. Ablation
  5. Ride the solar winds
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10
Q

Describe the Asteroid Belt

A
  • btwn Mars and Jupiter
  • rocky/metallic rocks, some are dwarf planets like Ceres
  • four largest asteroids:
    Ceres Vesta Palla Hygiea
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11
Q

Kuiper belt

A
  • just past Neptune orbit
  • larger than asteroid belt
  • ices like water, methane, ammonia
  • more dwarf planets like Pluto
  • some of our moons are thought to have originated here
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12
Q

Oort Cloud

A
  • 1000x farther from the sun. halfway to Alpha Centauri
  • edge of solar system
  • mostly ices
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13
Q

Meteor influx

A
  • logarithmic relationship between obj size and avg recurrence time
  • 100 billion meteoroids enter earth everyday
  • on average: 10km obj impact earth every 100 Million yrs

-> smaller = more common, larger = less common

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14
Q

impacts on earth vs moon

A

190 compared to like 9k

Earth: near northern hemisphere, all on land

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15
Q

Shoemaker’s Hypothesis

A
  1. sudden geological changes can arise from asteroid strikes
  2. over geological timescales, asteroid strikes are common
  3. impact craters form large, circular structures
    -> associated with ejecta, shocked quartz, iridium
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16
Q

What crater did the shoemakers study?

A

Ries Crater in Germany

  • building stone was suevite (rock mixed with partly melted materials)
  • 14 Ma created by 1.5km asteroid
16
Q

What crater did the shoemakers study?

A

Ries Crater in Germany

  • building stone was suevite (rock mixed with partly melted materials)
  • 14 Ma created by 1.5km asteroid
17
Q

R&S Nemesis

A

companion star

  • Sun has nemesis beyond Oort Cloud, orbit comes close ever 25 Myr
  • Gravitational effects kick comets to inner solar system
  • no evidence at all
18
Q

R&S Planet 9

A

Distant planet far beyond Neptune shift the Oort Cloud as it orbits sun

  • no evidence, probably unlikely
19
Q

R&S Galactic Plane

A

Solar system orbit centre of galaxy
- galaxy has thickness of stars/stuff
- move through dense part may disrupt Oort cloud

20
Q

R&S Coincidence?

A
  • dating of extinctions and impacts not always accurate
  • spacing not always consistent
  • probably more impacts we didn’t know about cuz oceans
  • other factors also cause extinctions
21
Q

Civilization ending impacts occur randomly every ~___ yrs

A

1 million

22
Q

Recent impacts: Tunguska, Russia

A

1908 June 30

  • no impact crater or material found, could’ve bounced back out
  • air blast of smt with diameter 70m
  • largest historical impact that levelled 3km of forest, sent a shockwave around Earth twice
23
Q

Recent impacts: Chelyabinks Russia

A

2013 Feb 15

  • bolide
  • 20m diameter asteroid explode in atmosphere 30km above ground
  • entered atmosphere at 19km/s from direction of sun
24
Q

Near misses: Asteroid 2019OK

A

2019 July 25

  • 100m diameter
  • passed within 73k km of Earth (1/5 moons orbit, 2x orbit of satellites :O)
25
Q

Near misses: Asteroid 2005YU55

A

2011 Nov 8

  • 360m diameter
  • passed within 325k km (4/5th of moon’s orbit)
  • discovered 6 yrs before passed earth
26
Q

Near misses: Eastern Mediterranean Event

A

2002 June 6

  • meteor air burst above Mediterranean Sea in Europe
  • unknown obj, no fragments found
  • similar to small nuclear bomb
27
Q

Future event: Asteroid Apophis

A

will approach Earth on April 13, 2029

  • 370m diameter
  • will pass within 32k km (closer than satellites!)
  • but NASA doesn’t think it will hit earth
28
Q

Comet Shoemaker Levy 9

A

1993
discovered by shoemaker and David levy

  • Jupiter gravity broke comet apart in 1992 and collided 2 yrs later
  • if this hit earth, would’ve wiped out life to microbial level
  • ppl started taking impacts very seriously
29
Q

What acts as a cosmic vacuum cleaner

A

Jupiter, because it has large gravitational pull

30
Q

Impact hazard is unique cuz

A

potentially most devastating but can be entirely avoided

-> Important factor is time

31
Q

Mitigation - Fragmentation

A

blow asteroid up

  • landing on an asteroid (possible), drilling into it
  • risk of multiple impacts
  • takes long time to prepare
32
Q

Mitigation - Rapid Orbit Adjustment

A
  • smash a nuclear warhead / projectile into asteroid
  • needs a warning period
33
Q

Mitigation - Gradual Orbit Adjustment

A
  • excavate material off the asteroid
  • use chemical. electric, nuclear propulsion
  • needs warning period
  • predictable method
34
Q

Mitigation - Ablation

A
  • flash-vaporize away the asteroid mass or deflect its path
  • focus sunlight on surface of asteroid / use lasers
  • need satellite in orbit around asteroid (possible)
35
Q

Mitigation - Ride solar winds

A
  • install solar sails on asteroid
  • radiative pressure from sunlight will deflect it
  • requires very long warning time
  • NASA scout mission will test in 2023
36
Q

Mitigation - Reality

A

all methods require research, lots of warning time, and lots of money

we have other problems to deal with…

EOSC 114 (30 decks)

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