Impacts 4

Question 1

Meteoroids

Answer 1

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

Question 2

Bolides

Answer 2

a type of Meteoroid, fireballs that explode in the atmosphere

Question 3

Asteroids

Answer 3

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

Question 4

Comets

Answer 4

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

Question 5

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

Answer 5

• 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

Question 6

Describe the raup and sepkoski hypothesis

Answer 6

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

Question 7

List and describe some recent impacts and near misses

Answer 7

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

Question 8

Briefly describe what is being done right now (impacts)

Answer 8

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

Question 9

List possible mitigation strategies

Answer 9

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

Question 10

Describe the Asteroid Belt

Answer 10

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

Question 11

Kuiper belt

Answer 11

• 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

Question 12

Oort Cloud

Answer 12

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

Question 13

Meteor influx

Answer 13

• 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

Question 14

impacts on earth vs moon

Answer 14

190 compared to like 9k

Earth: near northern hemisphere, all on land

Question 15

Shoemaker’s Hypothesis

Answer 15

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

Question 16

What crater did the shoemakers study?

Answer 16

Ries Crater in Germany

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

Question 16

What crater did the shoemakers study?

Answer 16

Ries Crater in Germany

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

Question 17

R&S Nemesis

Answer 17

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

Question 18

R&S Planet 9

Answer 18

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

• no evidence, probably unlikely

Question 19

R&S Galactic Plane

Answer 19

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

Question 20

R&S Coincidence?

Answer 20

• 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

Question 21

Civilization ending impacts occur randomly every ~___ yrs

Answer 21

1 million

Question 22

Recent impacts: Tunguska, Russia

Answer 22

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

Question 23

Recent impacts: Chelyabinks Russia

Answer 23

2013 Feb 15

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

Question 24

Near misses: Asteroid 2019OK

Answer 24

2019 July 25 - 100m diameter - passed within 73k km of Earth (1/5 moons orbit, 2x orbit of satellites :O)

Question 25

Near misses: Asteroid 2005YU55

Answer 25

2011 Nov 8 - 360m diameter - passed within 325k km (4/5th of moon's orbit) - discovered 6 yrs before passed earth

Question 26

Near misses: Eastern Mediterranean Event

Answer 26

2002 June 6 - meteor air burst above Mediterranean Sea in Europe - unknown obj, no fragments found - similar to small nuclear bomb

Question 27

Future event: Asteroid Apophis

Answer 27

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

Question 28

Comet Shoemaker Levy 9

Answer 28

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

Question 29

What acts as a cosmic vacuum cleaner

Answer 29

Jupiter, because it has large gravitational pull

Question 30

Impact hazard is unique cuz

Answer 30

potentially most devastating but can be entirely avoided -> Important factor is time

Question 31

Mitigation - Fragmentation

Answer 31

blow asteroid up - landing on an asteroid (possible), drilling into it - risk of multiple impacts - takes long time to prepare

Question 32

Mitigation - Rapid Orbit Adjustment

Answer 32

- smash a nuclear warhead / projectile into asteroid - needs a warning period

Question 33

Mitigation - Gradual Orbit Adjustment

Answer 33

- excavate material off the asteroid - use chemical. electric, nuclear propulsion - needs warning period - predictable method

Question 34

Mitigation - Ablation

Answer 34

- 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)

Question 35

Mitigation - Ride solar winds

Answer 35

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

Question 36

Mitigation - Reality

Answer 36

all methods require research, lots of warning time, and lots of money we have other problems to deal with...