Meteorites, Asteroids, and Comets

Please pick up your transmitter and swipe your ID

Meteorites

Distinguish between:

• Meteoroid = small body in space

• Meteor = meteoroid colliding with Earth and producing a visible light trace in the sky

• Meteorite = meteor that survives the plunge through the atmosphere to strike the ground

Which one of those objects would appear as a “shooting star”?

1 2 3 4 5 6 7

0% 0% 0% 0%0%0%0%

:10

0 of 30

1. Only meteoroids.

2. Only meteors.

3. Only meteorites.

4. Meteors and meteoroids.

5. Meteors and meteorites.

6. Meteoroids and meteorites.

7. All three.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

Meteorites

About 2 meteorites large enough to produce visible

impacts strike the Earth every day.

Statistically, one meteorite is expected to

strike a building somewhere on Earth

every 16 months.

Typically impact onto the atmosphere with 10 – 30 km/s (≈ 30 times faster than a rifle bullet).

Sizes from microscopic dust to a few centimeters.

Meteor ShowersMost meteors appear in showers, peaking periodically at specific dates of the year.

Meteoroid Orbits

Meteoroids contributing to a meteor shower are debris particles, orbiting in the path of a comet.

Spread out all along the orbit of the comet.

Comet may still exist or have been destroyed.

Only few sporadic meteors are not associated with comet orbits.

What kind of pattern would you expect to see, comparing the tracks of various meteors of one shower?

1 2 3 4

25% 25%25%25%

:10

0 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

1. The tracks should have random directions.

2. The tracks should all be parallel.3. The tracks should all appear to

come from the same point in space.4. The tracks should all appear to

move toward the same point in space.

Radiants of Meteor ShowersTracing the tracks of meteors in a shower backwards,

they appear to come from a common origin, the radiant.

↔ Common direction of

motion through space.

The Perseid Meteor Shower

The Leonid Meteor Shower in 2002

Would you expect a meteor shower to be equally intense each year?

1 2 3 4

25% 25%25%25%

:10

0 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

1. Yes, because all the meteors should orbit the sun in about 1 year, so there should be no fluctuations from year to year.

2. Yes, because the meteors are evenly distributed over the entire former comet orbit.

3. No, because the meteors should be concentrated around the former location of the comet, which orbited around the sun with a longer period than 1 year.

4. No. In fact, they should only be visible in one year at all.

Meteorite Impacts on EarthOver 150 impact craters found on Earth.

Famous example: Barringer

Crater near Flagstaff, AZ:

Formed ~ 50,000 years ago by a meteorite of ~ 80 – 100 m diameter

The Origins of Meteorites

Planetesimals cool and differentiate;

Collisions eject material from different depths with different

compositions and temperatures.

Meteorites can not have been broken up from planetesimals very long ago

→ Remains of planetesimals should still exist.

→ Asteroids

Asteroids

Last remains of planetesimals that built the planets 4.6 billion years

ago!

Where do we find most asteroids in the solar system?

1 2 3 4 5

20% 20% 20%20%20%

:10

0 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

1. In a belt between the Earth and Mars.

2. In a belt between Mars and Jupiter.

3. In a belt far outside the orbits of the planets.

4. On highly elliptical orbits, coming as close to the sun as Mercury’s orbit, and reaching as far out as Pluto’s orbit or beyond.

5. In elliptical orbits around Jupiter.

The Asteroid Belt

Plu

toN

eptu

neUra

nus

Saturn

Jupi

terM

ars

(Distances and times reproduced to scale)

Most asteroids orbit the sun in a

wide zone between the

orbits of Mars and Jupiter.

The Asteroid Belt

Sizes and shapes of the largest asteroids, compared to the moon

Small, irregular objects, mostly in the

apparent gap between the orbits of

Mars and Jupiter.

Thousands of asteroids with

accurately determined orbits are known today.

What causes the divisions (e.g., Cassini Division) in the rings of Saturn?

1 2 3 4

25% 25%25%25%

:10

0 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

1. Orbital resonances with moons orbiting Saturn outside the ring system.

2. Material close to an orbit of a moon inside the ring system being swept up by the moon.

3. Random fluctuations causing some regions around Saturn to be empty.

4. Orbital resonances with moons orbiting Saturn inside the ring system.

Kirkwood GapsThe asteroid orbits are not evenly distributed throughout

the asteroid belt between Mars and Jupiter.

There are several gaps where no asteroids are found:

Kirkwood gaps

These correspond to resonances of the orbits with the

orbit of Jupiter.

Example:

2:3 resonance

Non-Belt Asteroids

Apollo-Amor Objects:

Not all asteroids orbit within the asteroid belt.

Asteroids with elliptical

orbits, reaching into

the inner solar system.

Some potentially

colliding with Mars or Earth.

Trojans: Sharing stable

orbits along the orbit of

Jupiter.

Please pick up your transmitter and swipe your ID

Comets

Comet Ikeya-Seki in the dawn sky in 1965

Throughout history, comets have been considered as portants of doom, even until very recently:

Appearances of comet Kohoutek (1973), Halley (1986), and Hale-Bopp (1997) caused great concern

among superstitious.

Comet Hyakutake in 1996

Where on its orbit does a comet spend

most of its time? :10

0 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

1

2

4

3

1 2 3 4

25% 25%25%25%

Two Types of Tails

Ion tail: Ionized gas pushed away from the

comet by the solar wind. Pointing straight away

from the sun.

Dust tail: Dust set free from vaporizing ice in

the comet; carried away from the comet by the

sun’s radiation pressure. Lagging behind the

comet along its trajectory

Enter question text...

:10

0 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

Where is the sun with respect to

this comet?2)

3)

4)

5)

1)

1 2 3 4 5

20% 20% 20%20%20%

Gas and Dust Tails of Comet Mrkos in 1957

Comet Hale-Bopp in 1997

Fragmentation of Comet NucleiComet nuclei are very fragile and are easily fragmented.

Comet Shoemaker-Levy was disrupted by tidal forces of Jupiter

Two chains of impact craters on Earth’s moon and on Jupiter’s moon Callisto may have been caused by fragments of a comet.

Animation 1

Animation 2

Fragmenting CometsComet Linear

apparently completely vaporized during its

sun passage in 2000.

Only small rocky fragments remained.

The fragments of a comet can produce a new …

1 2 3 4 5

20% 20% 20%20%20%

:10

0 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116

1. Moon of Jupiter.

2. Moon of Mars.

3. Planet.

4. Meteor shower.

5. Group of asteroids.

The Geology of Comet NucleiComet nuclei contain ices of water, carbon dioxide, methane, ammonia, etc.

(Materials that should have condensed from the outer solar nebula).

Not solid ice balls, but fluffy material with

significant amounts of

empty space.

“Dirty snowballs”

The Deep Impact Mission

Video 1

Video 2

Placing a probe into the path of Comet Tempel 1 and documenting the result of the impact

Impact: July 4, 2005

The Origin of CometsComets are believed to originate in the Oort cloud:

Spherical cloud of several trillion icy bodies, ~ 10,000 – 100,000 AU from the sun.

40,000 – 100,000 AU

Oort Cloud

Gravitational influence of occasional passing

stars may perturb some orbits and draw them

towards the inner solar system.

Interactions with planets may perturb

orbits further, capturing comets in short-period orbits.

The Kuiper BeltSecond source of small, icy bodies in the outer solar system:

Kuiper Belt, at ~ 30 – 100 AU from the sun.

Pluto and Charon may be captured

Kuiper-Belt objects.

Beyond the Solar System