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ACM Exam 1
Exam 1 for ACM study material
| Question | Answer |
|---|---|
| Why do we consider chondrites primitive? What characteristics would you expect in a primitive meteorite? | Chondrules formed in the protoplanetary disk/solar nebula, not in the parent body. Therefore, chondrules capture the composition of the portion of the solar nebula from which they formed. Would expect chondrules, unequilibrated minerals, volatiles. |
| How are asteroid families defined? | Orbital dynamics such as eccentricity, inclination, etc. Also composition (composition complements orbital dynamics) |
| What type are most inner belt asteroids? Outer? | Inner: S-complex. Outer: C-complex |
| What are the 3 broad classes of meteorites? | Stony, Stony-Iron, Iron |
| What kind of meteorites come from undifferentitiaded asteroids? Differentiated? | UD: chondrites D: achondrites,iron, stony irons |
| The Windmanstatten pattern is indicative of what? | Nickel content |
| What part of the differentiated asteroid do the following meteorites originate? Stony-Iron (Pallasite), Iron, Achondrite | SI: Core/mantle boundary Iron: Core Achondrite: crust |
| Why do we have so many ordinary chondrites? | Parent bodies are near mean motion resonances |
| What petrologic type are enstatites? | 3-7 |
| Why don't we have many carbonaceous chondrites? | Because they are Carbon rich and fry easily in the atmosphere |
| What does the petrological scale indicate? | 1 - most aqueous alteration 3- no alteration 7- most thermal alteration |
| How do we know meteorites originate from the Moon? Mars? | Moon- can compare composition to Apollo samples. Mars- glass inclusions trapped Martian atmosphere and we compared it to Viking's atmospheric comp measurements |
| What are some heating sources in asteroids for differentiation? | Al-26, accretion and impacts, core segregation and crystallization, and tidal forces |
| Why are all asteroids not differentiated? | Al-26 was not evenly distributed in the solar nebula so not all asteroids had enough Al-26 to differentiate |
| How can we use Oxygen isotope composition to classify meteorites? | Meteorites of the same group lie on the mass fraction line w slope of 0.5 and have similar isotope compositions. |
| Why is it important that chondrites have the widest range of d17 and d18? | Because it shows they sample a variety of regions in the solar nebula |
| Why do achondrites have the smallest O isotope range? | they all came from parent bodies that had enough Al-26 to differentiate |
| What does cosmic ray exposure age indicate? | how long ago the meteorite was liberated from the parent body |
| What does a higher He-3 abundance indicate? | Longer cosmic ray exposure |
| What is the Yarkovsky effect? | force exerted on the asteroid when sunlight is absorbed and rereleased |
| When does the Yarkovsky effect cause an asteroid's orbit to spiral inward? Outward? | in - retrograde rotation out - prograde rotation |
| What affect spectral measurements of asteroids? | space weathering, particle size, porosity, and temperature |
| Which meteorite classes do not lie on the mass fraction line with a slope of 0.52 when it comes to O-isotope comp? | CK, CO, and CV |
| What petrologic types are carbonaceous chondrites? | 1-7 |
| What petrologic types are R-chondrites and Ordinary Chondrites? | 3-7 |
| What is the difference between carbonaceous and ordinary chondrites? | Carbonaceous are 99% silicates (very carbon rich) while OC have more metal content |
| What petrological changes can shock cause? | cracks, partial melts, veins, breccias, changes in crystal structure, changes in reflectivity |
| What is a common mineral we look for shock effects in? | plagioclase feldspar |
| Why are iron meteorites over represented in our meteorite collection? | Iron meteorites survive entering the atmosphere better and more easily recognized as meteorites |
| What are some parameters that are used to define the groups of silicate bearing meteorites? | refractory lithophile element, FeO concentration in olivine, and O isotope composition |
| What parameter is used to define iron meteorite groups? | siderophile element concentrations |
| What meteorites would you study to better understand the Martian crust? | SNCs |
| What meteorites would you study to better understand the the original composition of the solar nebula? | primitive chondrites |
| What meteorites would you study to better understand the origin of earth and terrestrial planets? | Chondrites |
| What meteorites would you study to better understand the metal cores of terrestrial planets? | Irons |
| What meteorites would you study to better understand the age of the solar system? | chondrites w CAIs |
| What meteorites would you study to better understand the surface composition of differentiated asteroids? | Achondrites, namely the HEDs |
| How do we think that mesosiderites formed? | impact mixing of a core fragment on the surface of a basaltic asteroid |
| Which resonances are resposible for delivering most meteorites to Earth? | v_6 and 3:1 |
| What body is generally thought to be the parent body of HEDs? Ordinary Chondrites | 4 Vesta S asteroids |
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