Transcript Astronomy Journey to the Cosmic Frontier

Solar System Debris
Asteroids, Meteors, Comets
Meteors
• Meteor—the bright
streak of light that is
produced when a
piece of debris burns
in earth’s atmosphere
• Meteoroid—the piece
of debris (usually
smaller than 1 cm)
Meteorites
• Meteoroids strike earth’s
atmosphere going
20-160 thousand mph
• Burn in atmosphere
between 60 50 miles
above ground
• If debris is large enough
and doesn’t all burn, the
piece that strikes the
ground is the Meteorite
• To find…look in desert or
in Antarctica
• Not usually very large,
but…occasionally we get
bigger ones.
Why Meteor Showers Occur—
Earth orbits through a trail of debris
(usually left behind by comet or other parent)
Meteor Showers
Shower Name
Quadrantids
Lyrids
Date of Max
Parent Object
Jan. 3
Apr. 22
Comet Thatcher
Eta Aquarids
May 4
Delta Aquarids July 29
Perseids
Aug. 12
Orionids
Oct. 21
Leonids
Geminids
Nov. 16
Dec. 13
Comet SwiftTuttle
Comet Halley
CometTempel-Tuttle
Asteroid Phaethon
Types of Meteorites
• Stony meteorites—94% of all that fall to Earth
(most are chondrites…named for chondrules of
glassy silicates inside)
• Iron meteorites—5% of meteorites that fall to Earth
(nearly pure iron and nickel)
• Stony-iron meteorites—1% that fall to earth
• Age of meteorites is about 4.5 billion yrs. old…left
over from solar system formation
• Parent bodies…asteroids
The Possible Evolution of a Parent
Body of Meteorites
What happens if a REALLY big meteorite makes it
through the atmosphere and hits a planet?
Meteor Crater (Winslow, AR)
Crater is almost 1 mile across…produced by a meteorite that
was ~150 ft. in diameter
So what would happen if….
Impact Diameter (m) Yield (megatons) Interval (yrs.)Consequences
~10 m
<10
~10 years
most break apart
75
10-100
1000 yrs.
irons like Meteor Crater
stones like Tunguska
150 m
1000-10,000
~5,000 yrs. land impacts destroy size
of small state
700
10,000-100,000
~5,000 yrs. land impacts destroy size
of moderate state (VA)
1700
100,000~300,000 yrs. land impacts destroy size
1,000,000
of CA or France..dust
source:ht t p:/ / impact .arc.nasa.gov/ downloads/ spacesurvey.pdf
raises global implications
Note: Atomic Bomb on Nagasaki energy release= only 20 kilotons
H-Bomb release = ~60 Megatons
Q: When did this happen?
A: about 50,000 yrs. ago
Meteor Crater (Winslow, AR)
When’s the next one? …um, we don’t know…
Asteroids
• Asteroids—metallic, rocky bodies
without atmospheres that orbit the
Sun but are too small to be
classified as planets.
• How many are there?
• We now know orbits of
50,000…but we don’t know them
all
• Most are found in asteroid belt
between Mars and Jupiter
(2.1-3.3 AU)
• Lots of space in between them…
it’s not like Star Wars…they’re
about 5 million km apart
Asteroid Locations
7000 asteroids in
1997 (not to scale)
Trojan
asteroids
Trojan
asteroids
Jupiter
Do Asteroids come near Earth?
• Amor Asteroids—pass inside Mars’ orbit but don’t cross
Earth’s
• Aten asteroids—cross Earth’s path when furthest from sun
• Apollo asteroids—Earth crossing asteroids (largest known is
~8km in diameter)
The Size of Near-Earth Asteroids
What are the largest asteroids?
• Ceres (now classified as a dwarf planet like
Pluto) is 1000 km in diameter (see image)
• Pallas and Vesta are both ~500 km in
diameter
The asteroid Toutatis has
dimensions of
2.9 x 1.5 x 1.2 miles
951 Gaspra—dimensions of
18.2×10.5×8.9 km
433 Eros—dimensions of
13 × 13 × 33 km
Near Earth Asteroid Rendezvous
(NEAR) mission visited and
landed on Eros in 2000
The Chicxulub
Impact Structure
100-150 mile diameter crater off
Yucatan Peninsula dating back to
65 millions years ago…
So what? This is the same time as
dinosaur fossils; in layers of
sediment, there’s a concentration of
iridium worldwide from a settling
of a worldwide dust
Comets
• “Dirty Snowball”—
made of ice (frozen
water, CO2, CO,
formaldehyde),dust,
rock
The Parts of a Comet
The Orientation of
Comet Tails
Tail always points away
from the sun…so it can
lead the comet (like at
the right of the diagram)
Comet Halle-Bopp in 1997
(nucleus of 40 km)
Comet Hyakutake in 1996
(nucleus of 2 km)
Halley’s comet in 1986
(nucleus of 15 km)
The Oort Cloud
Stellar Perturbations
Kuiper Belt Comets
Comet Shoemaker-Levy 9
(impacted in 1994)
• 1994 string of a
comets broken apart
• fragments labeled A
through W heading
straight toward Jupiter
• real time impact
witnessed during our
lifetime
What it would have looked like
on Earth compared to Jupiter
1. Graph radius of crater (y-axis) vs. height of drop (x-axis).
Remember to make your graph with labels, units, and evenly
marked out intervals.
2. Graph radius of crater (y-axis) vs. mass of sphere (x-axis).
Remember to make your graph with labels, units, and evenly
marked out intervals.
Conclusion Questions
1. Is there a trend to your graphs and your data? Explain.
2. We varied the height (and indirectly, the speed) and the mass of the
asteroid. What might be other factors we did not consider that may
also affect the size of craters left behind by an asteroid? (think of at
least 2)
3. For the 2 factors that you listed above, give a hypothesis for each.
How do you think these factors would affect the crater’s size?
4. In addition to the radii of the craters, what other qualities of the
craters could be measured or studied?
5. How do you think the angle of impact might affect the size or shape
of the crater left behind? Provide sketches in addition to words to
answer this question.
6. In scientific terms, how have comets and asteroids played a role in the
evolution and development of the terrestrial planets in our solar
system? Be specific for each planet: Mercury, Venus, Earth, Mars,
and the Moon.