A1 13 Asteroids

AsteroidsLACC: 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?

1Thursday, March 25, 2010

Asteroids

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




Asteroids

http://rocksfromspace.open.ac.uk/images/Asteroids_Sullivan.jpg

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 material that never coalesced into a 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 diameter of our Moon.

cometcomet

Mars’smoon

Mars’smoon

Mars’smoon




Asteroid Belt

http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=850

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.




Asteroid Position and Gravitational Resonances

http://www.physics.uc.edu/%7Esitko/AdvancedAstro/25-SmallBodies/SmallBodies.htm

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.




Types of Asteroids by Composition

http://www.nineplanets.org/asteroids.html

• 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/help.html#volatile

http://www.nineplanets.org/help.html#volatile

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.




Asteroids: Ida and its moon Dactyl

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




Asteroids: Eros

http://nssdc.gsfc.nasa.gov/planetary/near.html

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,.




Asteroids: Near Earth Asteroid Itokawa

http://www.muses-c.isas.ac.jp/e/index_31.html

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




AsteroidsLACC: 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).



• Ch 13, p. 308: 2.

Due at the beginning of first class period after this week.

Be working your Solar System project.

LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,

3rd ed.


MeteoritesLACC: 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



Meteor/Meteoroids/Meteorites

http://www.physics.uq.edu.au/people/ross/phys2081/meteor.htm

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.




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

•Stoney Iron (Si/Fe/Ni -pretty rare).

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://rst.gsfc.nasa.gov/Sect19/Sect19_2.html

% by falls ± a few %






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

http://www.meteorlab.com/METEORLAB2001dev/carbchon.htm

[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/glossary.htm#INCLUSION

http://www.meteorlab.com/METEORLAB2001dev/glossary.htm#INCLUSION

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.




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


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

meteorite asteroid




Meteorites: Close CallsA 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.daviddarling.info/encyclopedia/P/Peekskill_meteorite.html

http://www.youtube.com/watch?v=IMaAjoMjj9w


http://www.daviddarling.info/encyclopedia/M/meteorite.html

http://www.daviddarling.info/encyclopedia/M/meteorite.html

http://www.daviddarling.info/encyclopedia/C/chondrite.html

http://www.daviddarling.info/encyclopedia/C/chondrite.html

http://www.daviddarling.info/encyclopedia/F/fireball.html

http://www.daviddarling.info/encyclopedia/F/fireball.html







Meteorites: Close Calls

http://uanews.ua.edu/anews2004/nov04/meteorite112404.htm

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.

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.


MeteoritesLACC: 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



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A1 13 Asteroids

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