A1 13 Asteroids

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

Asteroids

http://hubblesite.org/newscenter/archive/releases/2005/27/image/b/format/web_print/

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

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


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


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


Asteroid Densities

http://aa.usno.navy.mil/faq/docs/asteroid_masses


Asteroids: Ceres

http://www.solarviews.com/eng/ceres.htm

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


Asteroids:
Ida and its moon Dactyl

http://www.solarviews.com/eng/ida.htm

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


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

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?


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.


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?


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


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-]


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.

Primitive Meteorite Composition

http://eps.berkeley.edu/cig/depaolo/eps102/PPT4_Meteorites.html


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

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

Processed Meteorites: Origin

https://www.dmr.nd.gov/ndgs/Geology%20Notes/Meteor/meteor.asp

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.


(Asteroid) Vesta Meteorites

meteorite asteroid

At least one meteorite has been traced to a speciﬁc asteroid,
Vesta, based on strong similarities in spectral properties



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


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


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.


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?


A1 13 Asteroids

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