Impacts

Question 1

what is an asteroid?

Answer 1

a small (less than 1000 km) rock/metal rich body orbiting the sun

Question 2

how many asteroids exists? vs the number identified?

Answer 2

millions vs 10,000

Question 3

most asteroids are in the asteroid belt (some are near earth orbits). where is the belt?

Answer 3

between mars and jupiter

Question 4

what is a comet?

Answer 4

a small (less than 10 km) ice & dust object orbiting around the sun

Question 5

where are comets formed? where do they reside?

Answer 5

-past the orbit of jupiter
-outer solar system (Kuiper Belt -neptune and Oort Cloud)

Question 6

what is a meteroite? there are two meanings. (on earth vs techinically)

Answer 6

-on earth: an extraterrestial rock
-technically: solid matter that has fallen to earth, moon, or other planet

Question 7

what is a meteoroid? speed?

Answer 7

rock that enters the atmosphere from space (before it hits the ground)
16-42 km/s (58000-150000 km/h)

Question 8

what happens as a meteroid enters the atmosphere?

Answer 8

it slows and fragments because of friction (produce light of different colour and heat)

Question 9

what is a meteor?

Answer 9

the atmospheric phenomenon created by meteoroid (aka the light, aka shooting star, aka fireball)

Question 10

what is a fireball?

Answer 10

a really bright meteror (light of different colours)

Question 11

how many meteroites per day?

Answer 11

100 tons/day

Question 12

what happens with meteoroid loses its cosmic velocity

Answer 12

ablate completely, fragments, slows —> meteorites (no reall damage)

Question 13

what happens with meteoroid keeps its cosmic velocity

Answer 13

impacts surface at more than 12km/s -> impact crater

Question 14

what is the source for most meteroites?

Answer 14

asteroids (hazardous if close to earth and large enough)

Question 15

what are NEOs

Answer 15

Near Earth Objects (asteroids or comets)
whose orbits bring them within 50 million km of
Earth.

Question 16

what are PHAs

Answer 16

Potentially Hazardous Asteroids, that come
within 7.5 million km of Earth and are > 140 m
across

Question 17

what are largest resident of the belt?

Answer 17

ceres (946 km)
vesta (525 km)
they are protoplanets

Question 18

what is the dawn mission?

Answer 18

mission by nasa launched in sep 27, 2007 using ion propulsion engine to investigate the asteroids vesta and ceres (ended nov 1, 2018)

Question 19

what did dawn capture?

Answer 19

colour photograph, topographic map, elemental and mineral composition, gravity field

Question 20

vesta has two impact basins. what are they?

Answer 20

-Rheasilvia’s central peak is more than twice the height of Mt. Everest (500 km , 1 bya)
-veneneia (400 km, 2 bya)

Question 21

vesta has a core of ____ km diamater

Answer 21

220

Question 22

ceres before dawn mission suggested what?

Answer 22

featureless ball (75% rock and the rest ice)

Question 23

dawn mission:ceres

Answer 23

similar crater pop’n as vesta but large basins are not present

Question 24

ceres hidden interior

Answer 24

-icy crust indicates differentiation
-strong shell (40-50 km thick) made of ice, salts, silicates with soft muddy mantle Irocky)

Question 25

OSIRIS-REx mission

Answer 25

sampled bennu asteroid (rubble pile has breccias)

Question 26

bennu mineral composition? ejection? spin rate? age?

Answer 26

-hydrated mineal (chondrites)
-ejected particles into space
-spin rate increasing over time
-100 million to 1 billion

Question 27

what is a rubble pile asteroid?

Answer 27

asteroid made from other asteroids

Question 28

Bennu and Ryugu are ____

Answer 28

PHAs

Question 29

Sample return from Ryugu and Bennu can:____ (2)

Answer 29

– Provide links between asteroids and meteorites
– Provide information on the physical properties of PHA

Question 30

Ryugu is most like a -_______

Answer 30

CI chondrite meteorite

Question 31

the moon was formed by what?

Answer 31

giant impact 50 ma after earth was formed

Question 32

how many craters formed on mars in the last 10 years

Answer 32

400

Question 33

bolide aka ____

Answer 33

meteorite/comet

Question 34

what are the stages of impact cratering

Answer 34

Compression (Shock wave expands out from
point of impact, Compresses rock to 1/3 its usual
volume, Rock can flow like a fluid)
Excavation (decompression wave follows shock front, target rock and bolide vaporized, flow, spray out of transient cavity, eject ravels out as conical sheet, crater rim overturned)
Modification (larg ones only, gravity can’t sustain cavity so walls slumps and central uplift occurs)

Question 35

the bolide is typically _____ in impact

Answer 35

destroyed

Question 36

features of impact cratering

Answer 36

• Ejecta blanket, (sometimes) rays
• Overturned rim
• Impact melt sheet
• (sometimes) Central uplift (peaks or rings)
  ejecta rays, secondary craters,
  tektites (glass)
  breccia

Question 37

The Cretaceous-Paleogene (K-Pg) Impact Event

Answer 37

-hit yucatan peninsula, 66 mya
-tsunami (global)
-melted rock falling = fires
-75 % of plant and animals species died out
crater: chicxulub is 180 km (one of largest on earth)

Question 38

hazard vs risk

Answer 38

-something that may cause death, injury or other impacts (can be single, sequential)
-probability that hazard causes damage

Question 39

hazards are either anthropogenic or non-anthropogenic?

Answer 39

-war, global warming, famine etc.
-pandemic (kinda), solar flar, volcanism, impact

Question 40

What can we do to mitigate the risk of impact?

Answer 40

1. OBSERVE (The more we look, the more we can identify PHAs and determine their orbits)
2. Plan (Since 2013 there have been >10 exercises involving hypothetical simulations carried out by the planetary defense community)
3. Prepare (Develop technology to deflect a PHA)

Question 41

There are ~_____impact craters recorded in Earth’s crust

Answer 41

-200

Question 42

The NASA DART Mission

Answer 42

-►Double Asteroid Redirect Test (NASA first planetary defence mission)
purpose: show that asteroid could be deflected by kinetic impact