1. Asteroids
LACC: Ch §12.1, 13.1, 13.2
• Understand what conditions and processes
shaped the asteroid belt
• Understand how Asteroids are classified
• Know the Asteroid that is a dwarf planet
An attempt to answer the “big questions”: what is
out there? Are we alone?
Thursday, March 25, 2010 1
2. Asteroids
http://hubblesite.org/newscenter/archive/releases/2005/27/image/b/format/web_print/
Thursday, March 25, 2010 2
3. n
Asteroids
Mars’s
moon
Asteroids are material left over from
the formation of the solar system. One
theory suggests that they are the
remains of a planet that was
destroyed in a massive collision long
ago. More likely, asteroids are
Mars’s material that never coalesced into a
moon planet. In fact, if the estimated total
mass of all asteroids was gathered
into a single object, the object
would be less than 1,500 kilometers
(932 miles) across, less than half the
comet diameter of our Moon.
comet
http://rocksfromspace.open.ac.uk/images/Asteroids_Sullivan.jpg
Thursday, March 25, 2010 3
4. Asteroid Belt
The asteroid belt lies in the region
between Mars and Jupiter. The
Trojan asteroids lie in Jupiter's
orbit, in two distinct regions in
front of and behind the planet.
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=850
Thursday, March 25, 2010 4
5. Asteroid Position and
Gravitational Resonances
Note: while some
resonances tend to
move the semi-
major axis out of a
particular value,
others favor
having objects at
the resonance with
Jupiter. Among these
are the 3:2, 4:3, and 1:1.
The 1:1 resonance is
the location of the
Trojan asteroids.
http://www.physics.uc.edu/%7Esitko/AdvancedAstro/25-SmallBodies/SmallBodies.htm
Thursday, March 25, 2010 5
6. Types of Asteroids by
Composition
• C-type, includes more than 75% of known asteroids: extremely
dark (albedo 0.03); similar to carbonaceous chondrite
meteorites; approximately the same chemical composition as the
Sun minus hydrogen, helium and other volatiles;
• S-type, 17%: relatively bright (albedo .10-.22); metallic nickel-iron
mixed with iron- and magnesium-silicates;
• M-type, most of the rest: bright (albedo .10-.18); pure nickel-iron
[metals].
• There are also a dozen or so other rare types.
Because of biases involved in the observations (e.g. the dark C-types
are harder to see), the percentages above may not be representative of
the true distribution of asteroids. (There are actually several classification
schemes in use today.)
http://www.nineplanets.org/asteroids.html
Thursday, March 25, 2010 6
7. Asteroid Densities
http://aa.usno.navy.mil/faq/docs/asteroid_masses
Thursday, March 25, 2010 7
8. Asteroids: Ceres
http://www.solarviews.com/eng/ceres.htm
Thursday, March 25, 2010 8
9. Asteroids: Ceres
With a diameter of about 975x909 km, Ceres is by far the largest and most
massive body in the asteroid belt, and contains approximately a third of
the mass of all the asteroids in the solar system. Recent observations have
revealed that Ceres is nearly spherical in shape, unlike the irregular shapes of
smaller bodies with less gravity. Having sufficient mass for self-gravity to
overcome rigid body forces is one of the requirements for classification as a
planet or dwarf planet.
Ceres has a very primitive surface and like a young planet, contains water-
bearing minerals, and possibly a very weak atmosphere and frost. Infrared
observations show that the surface is warm with a possible maximum
temperature of 235 K (-38°C).
NASA's Hubble Space Telescope observed that Ceres' surface has a large dark
spot as well as a bright spot which are presumed to be craters. A second
explanation for the dark spot it that it may be a darker substance in the
asteroid's soil. Studies have shown that Ceres probably has a differentiated
interior with a rocky core, an icy mantle that is between 60 to 120 km thick,
and a thin dusty surface.
http://www.solarviews.com/eng/ceres.htm
Thursday, March 25, 2010 9
10. Asteroids:
Ida and its moon Dactyl
http://www.solarviews.com/eng/ida.htm
Thursday, March 25, 2010 10
11. Asteroids: Eros
NEAR Shoemaker touched down on the surface of Eros at 3:01:52 p.m.
EST (20:01:52 UT) Monday, 12 February [2001].... The spacecraft
impacted at a velocity of about 1.5 to 1.8 m/s (3.4 to 4.0 mph). The
spacecraft obtained 69 high-resolution images before touchdown, the
final image showing an area 6 meters across. NEAR was not designed as
a lander, but survived the low-velocity, low-gravity impact,.
http://nssdc.gsfc.nasa.gov/planetary/near.html
Thursday, March 25, 2010 11
12. Asteroids:
Near Earth Asteroid Itokawa
The density has been estimated to be 2.3
+/-0.3 gram/cc, which is a little lower than
that measured for rocks on the ground or
for other S-type asteroids measured to
date. This may indicate that there is
substantial porosity for this body
http://www.muses-c.isas.ac.jp/e/index_31.html
Thursday, March 25, 2010 12
13. Asteroids
LACC: Ch §12.1, 13.1, 13.2
• Understand what conditions and processes
shaped the asteroid belt: Jupiter’s influence (or
a massive collision destroyed a planet)
• Understand how Asteroids are classified:
composition (usual spectral analysis) and
location (gravitation resonances)
• Know the Asteroid that is a dwarf planet: Ceres
(1/3 mass of all asteroid belt).
An attempt to answer the “big questions”: what is
out there? Are we alone?
Thursday, March 25, 2010 13
14. LACC HW: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.
• Ch 13, p. 308: 2.
Due at the beginning of first class period
after this week.
Be working your Solar System project.
Thursday, March 25, 2010 14
15. Meteorites
LACC: Ch §12.1, 13.1, 13.2
• Know where Meteorites and Meteors come from
• Know how Meteorites are classified
• Know what Meteorites tell us about the conditions
and processes shaped our solar system
An attempt to answer the “big questions”: what is out
there? Are we alone?
Thursday, March 25, 2010 15
16. Meteor/Meteoroids/Meteorites
It is estimated that 1,000 tons to more than 10,000 tons of interplanetary material falls on
the Earth each day. Most of this material is very tiny in the form of micrometeoroids or
dust-like grains a few micrometers in size. These particles are so tiny that the air
resistance is enough to slow them sufficiently that they do not burn up, but rather fall
gently to Earth.
"Shooting stars" or meteors are bits of material falling through Earth's atmosphere
at altitudes of 50-100 km. They are heated to incandescence by [ram pressure]. The
surface melts and vaporizes leaving behind an ionized trail of gas and dust. The bright
trails as they are coming through the Earth's atmosphere are termed meteors,
and these chunks as they are hurtling through space are called meteoroids. As
the object penetrates to 20 km it will have slowed enough that heating no longer makes
it glow and it will continue to fall to Earth. Large pieces that do not vaporize
completely and reach the surface of the Earth are called meteorites.
On occasions a large meteoroid will strike the earth and at 120 km glow as bright as the
sun. These fireballs are called bolides and often are accompanied by sonic booms.
http://www.physics.uq.edu.au/people/ross/phys2081/meteor.htm
Thursday, March 25, 2010 16
17. Types of Meteorites by
Composition
• Iron (Fe/Ni) are the most
likely finds (they look more
unusual),
• Stony (C/O/Mg/Si) are the
most likely falls (the most
common type) and
% by falls • Stoney Iron (Si/Fe/Ni -
± a few % pretty rare).
http://rst.gsfc.nasa.gov/Sect19/Sect19_2.html
The stony meteorites are further subdivided into chondrites and
achondrites. Most meteorites are chondrites, so named because of the
presence of small rounded grains called chondrules. These grains are a
few mm diameter and rich in olivine and pyroxine. [silicates, e.g. SiO42-]
http://www.physics.uq.edu.au/people/ross/phys2081/meteor.htm
Thursday, March 25, 2010 17
18. Carbonaceous Chondrites
A few chondrites have high concentrations of Al, Mg and
Ca, and rich in O, and have almost no metallic Fe-Ni.
These meteorites are dark in color and called
carbonaceous chondrites. ...the composition matches
the non volatile composition of the sun. If you took the
primordial material of the solar system, as we suspect the
sun is composed, then condense it, discarding volatiles
such as H and He, you would end up with such material.
This mixture is called "chondritic". Carbonaceous
chondrites are some of the most complex of all
meteorites. They are rare, primitive and contain organic
compounds. Most importantly they contain water-bearing
minerals which is evidence of water moving slowly through
their interiors not long after formation.
http://www.physics.uq.edu.au/people/ross/phys2081/meteor.htm
Thursday, March 25, 2010 18
20. Section of the Allende, Mexico
CV3 meteorite
[This carbonaceous chondrite is] classed as CV3 and represents some
of the oldest known matter. The meteorite formed 4.56 billion years
ago and contains interstellar grains within calcium/aluminum rich
inclusions (CAIs). Interstellar grains are remnants of a prior star that lived
out its life and exploded before the formation of our Sun. It is possible
that this explosion was the trigger for the formation of our solar system.
http://www.meteorlab.com/METEORLAB2001dev/carbchon.htm
Thursday, March 25, 2010 20
21. The Murchison, Australia,
carbonaceous chondrite, CM2
[This carbonaceous chondrite is] a CM2 chondrite and believed to be of
cometary origin because of its high water content, 12%. To date 92
amino acids (the building blocks of protein) have been found in
Murchison. Only nineteen of them are found on Earth.
http://www.meteorlab.com/METEORLAB2001dev/carbchon.htm
Thursday, March 25, 2010 21
22. Processed Meteorites: Origin
https://www.dmr.nd.gov/ndgs/Geology%20Notes/Meteor/meteor.asp
Thursday, March 25, 2010 22
23. Lunaites (Moon Meteorites)
There is a growing realization that many of the Achondrites may
be pieces of the Moon or Mars expelled from these bodies by
impact. Lunar meteorites may directly strike the Earth after thrown
off by a lunar impact or fall after being captured in orbit... [Above
are] meteorite samples of probably lunar origin, as determined by
age and composition.
http://rst.gsfc.nasa.gov/Sect19/Sect19_2.html
Thursday, March 25, 2010 23
24. (Asteroid) Vesta Meteorites
meteorite asteroid
At least one meteorite has been traced to a specific asteroid,
Vesta, based on strong similarities in spectral properties
http://rst.gsfc.nasa.gov/Sect19/Sect19_2.html
Thursday, March 25, 2010 24
25. Meteorites: Close Calls
A 12.4 kg meteorite, classified as
an H6 chondrite, that fell in
Peekskill, New York, on Oct. 9,
1992, penetrating the trunk of a
1980 Chevy Malibu that was
sitting in its driveway. The descent
of the space rock was witnessed
by thousands in the eastern
United States as a brilliant fireball
and was caught on at least 14
amateur videotapes.
http://www.youtube.com/
watch?v=IMaAjoMjj9w
http://www.daviddarling.info/encyclopedia/P/Peekskill_meteorite.html
Thursday, March 25, 2010 25
26. Meteorites: Close Calls
Ed Howard, then Sylacauga mayor, Ann Hodges and then
Sylacauga Police Chief W.D. Ashcraft pose with a meteorite
underneath the point where it crashed through Hodges' house
in 1954. Hodges donated the meteorite to UA's Alabama
Museum of Natural History in 1956.
http://uanews.ua.edu/anews2004/nov04/
meteorite112404.htm
On the 30 March 1954 Mrs. Hodges was asleep on her sofa when a
3.86 kg (= 8.51 lbs unit conversion) stony meteorite crashed
though her roof [struck the radio, bounced off the floor] and hit
her, causing abdominal injuries which, fortunately, were not serious.
http://www.michaelbloodmeteorites.com/Hammers.html
Thursday, March 25, 2010 26
27. LACC HW: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.
• Ch 13, p. 308: 4.
Due at the beginning of first class period
after this week.
Be working your Solar System project.
Thursday, March 25, 2010 27
28. Meteorites
LACC: Ch §12.1, 13.1, 13.2
• Know where Meteorites and Meteors come from:
Meteors: mostly asteroids, sometimes comets (or
Moon/Mars); Meteors (mostly comet dust)
• Know how Meteorites are classified: composition
(laboratory analysis)
• Know what Meteorites tell us about the conditions
and processes shaped our solar system:
undifferentiated = primitive carbonaceous chondrites
vs. differentiated = processed irons
An attempt to answer the “big questions”: what is out
there? Are we alone?
Thursday, March 25, 2010 28