Geology of Planets Study Questions
When did linear rilles form on the Moon?
-only few formed after 3.5 billion years ago
What are some of the results of gravitational accretion of the planets? Specifically, describe the surfaces that result and how accretion affected the temperature of a planet
- -accretion causes the temperature to rise within the planet, which allowed differentiation to occur in various degrees
Describe the solar nebula from which the planets are thought to have formed.
-A large concentration of gas and dust (about 1000 atoms/cm3)
Besides these processes, what else modified Earth's atmosphere but didn't affect the atmospheres of any other planet or moon?
-A tertiary atmosphere modified the Earths atmosphere. This is because the life found on earth converts carbon dioxide to oxygen that we can breath.
How did the solids that condensed from the solar nebula accumulate to form large planets? a. What is the evidence for this process? b. What happened to the kinetic energy of the accreting material as it formed planets? c. What happened to the temperature of a planet as it accreted?
-Accretion occurred, meaning that many of these condensed solids joined together through collision and formed large planets A) evidence is in asteroids and other planetary bodies B) the kinetic energy from the collision converted to heat C) temperature of the planet increased drastically during accretion.
What processes and features are typical of a planet at various stages of its thermal history? When it is hot? When it is cool?
-Accretion, magma ocean, core formation, and outgassing warm the planet for the first part of its life, but over time it cools down and slows cooling as time goes on
Are any stony meteorites igneous rocks? Are any metamorphic rocks?
-Achondrites are igneous rocks -Chondrites have metamorphism
How do asteroids that orbit near Mars differ from asteroids that orbit near Jupiter?
-Asteroids further from the sun appear to be carbonaceous chondrites, and even some water ice -Asteroids closer to the sun are composed of iron and magnesium-rich silicate minerals, olivine and pyroxene
Compare the surfaces of two hypothetical planetary bodies with diameters of 5,000 km—the first is found in the inner part of a solar system, like ours, and the second is in the outer part of the system.
-Both planets are big enough to differentiate. -Both will not likely have a primary atmosphere due to their small size -The core of the inner planet will probably be metal, with a silicate mantle, and a crust -In contrast, the outer planet is likely to have a core of silicate, and a thick outer layer of ice.
Compare the densities of Ceres and Vesta. Explain what compositional characteristics might explain the difference in density. Now consider their positions in the asteroid belt. Are the density (composition) and the distance from the Sun somehow correlated?
-Ceres is 2.1 g/cm3, and Vesta is 3.42 g/cm3 —Ceres is composed of carbonaceous materials, like hydrous silicates and water ices which are less dense —Vesta is comprised of pyroxene-rich rocks like achondrite meteorites, which is denser. -We can see from the comparison of the inner and outer planets that further out from the sun, bodies seem to be larger, but less dense. This is the case with Ceres and Vesta as well.
What are the most important controls on the thermal (heating or cooling) history of a planet? A. How does surface area to mass ratio affect a planet's cooling rate? B. Which planets cool faster—small ones or large ones?
-Chemical composition -Accretion History (original temperature) -Mass -Size/diameter -Surface area to Mass ratio A. Smaller objects have a larger surface area to mass ratio, so the higher the ratio, the quicker the cooling B. Small planets cool faster
Draw a diagram of the internal structure of the Moon and briefly describe the crust, mantle, and core. How and when did this internal structure form? Did the Moon ever have a magnetic field?
-Crust: Average thickness is about 70 km, but range is 50 to 100 km -Mantle: Believed to be rich in olivine, pyroxene, iron, and magnesium. Thick and rigid - does not allow lateral movement (one-plate planet) -Core: Believed to be an iron core with a 400 to 700 km radius - -At one time, thermal convection within the core produced a magnetic dynamo. A magnetic field may have been produced at about the same time as mare basalts erupted.
What happens during the T-Tauri stage of a star's evolution?
-Extreme fluctuations in energy and a strong magnetic field are present -A large force clears out excess gas and dust
Under what conditions will hydrogen start to fuse to helium, and how does this compare with the conditions required for helium to fuse to form carbon or oxygen?
-H burns to produce He -He burns to produce C -C burns with He to produce O
What is the evidence that some stony meteorites are undifferentiated and similar in composition to the primitive solar nebula?
-Has elemental composition like solar nebula (similar to sun) —composition like sun (silicon, iron, magnesium) —Elements are too volatile to form minerals incorporated in meteorites
What processes may affect the composition and thickness of a secondary atmosphere after it is outgassed? Give examples of loss to space, condensation of atmospheric gases to form a liquid (hydrosphere), condensation of atmospheric gas to form a solid (cryosphere), and reaction of atmospheric gases with rocks on the surface.
-Hydrous solid (water contained in minerals) to anhydrous solid + gas -Trapped CO2, N2, H2O, Argon, H2S, CH4 (released by volcanism/magmatism) —Accumulated gas to the surface, or released to space if small planet) -Tertiary Atmosphere modifies secondary atmosphere through plant conversion of carbon dioxide to oxygen
Study the photographs of Gaspra, Ida, and Vesta What geologic processes formed their surface features? Why are they irregular in shape rather than spherical? Is there any evidence for volcanism or tectonism in the photos of Gaspra or Ida? Is this consistent with your expectations for such small bodies? Why do asteroids like Vesta and Ceres have so many impact craters?
-Impact cratering -Impact and partial fragmentation -Asteroids attempt to take on a spherical shape, but since they are small and have a low gravitational force, they can't become spherical -They are irregular because of mechanical processes, impact, and fragmentation -There doesn't seem to be any evidence of volcanism or tectonism —This is what would be expected because they don't have as complex of a structure as planets -Perhaps it is because they are very large so they have some gravitational pull. They also received a lot of collision during the heavy bombardment stage.
Explain the development of the inherited atmospheres of the outer planets. Contrast with secondary atmsophere
-Inherited atmospheres are thick and composed mostly of hydrogen and helium. Formed by gravitational capture of gaseous solar nebula. -Secondary atmospheres are thin and usually consist of carbon dioxide and water. Developed on some inner planets that held no nebular gas. —Heating cause partial melting and metamorphism. This released gases that, because of their low densities, rose to the surface of the planet.
In what ways could the Moon be considered a planet?
-It is a differentiated planet-like body —Has a crust, mantle, and possibly a small metal core —Has lithosphere, asthenosphere, no hydrosphere or atmosphere) and possibly small core -It is big enough to be round
Why did planets with compositions as different as those of Earth and Jupiter form from a solar nebula that may have had a uniform chemical composition?
-It is hotter near the protostar, so some elements could not solidify until they reached further distances from the Sun —Metals and silicates can exist as solids even at high temperatures, so the inner planets are generally made of these. —Ice must be away from heat to solidify, so the outer planets are composed of ices -Outer planets may be bigger because there was more volatile material in the nebula, and not as much silicates and metals. They also trapped gases into their atmosphere that were expelled during T-Tauri phase.
How does the lithosphere thickness affect the geologic activity at the surface of the Moon?
-It is nearly impossible for molten lava to reach the surface of the moon -prohibits lateral movements that cause continental shift -Moon quakes occur at the bottom of the lithosphere
How is the Moon different from the asteroids Gaspra, Ida, and Vesta?
-It's big enough to be round because it has enough of a gravitational pull, whereas the asteroids are not round -two terrain types (highlands and lowlands)
Why is Jupiter so large? How did its atmosphere originate?
-Jupiter is so large because it was the first planet formed after the snow line, meaning that it took a large portion of the volatile materials during the nebular phase of the solar system. (Composed largely of ice) -Because it was so large, it was capable of trapping gases (like hydrogen and helium) into its atmosphere and keep them from being blown away.
How was a T-Tauri stage related to the evolution of the nebula?
-Large amount of matter are ejected from the nebula -Wind sweeps uncondensed gas and light dust from inner part of evolving nebular disk -possibly the cause of the physical separation between gas and solids, causing material distribution
What are lunar sinuous rilles?
-Long winding valleys -100s km long, and 1-10 km wide, <.5 km deep -most occur along shallow edges of maria -many begin at a volcanic crater and progressively become smaller until they disappear -Some are V shaped, but flat floors complicated by inner channels, craters, and irregular hummocks are more typical -some may be fault-troughs modified by flowing lava
What is the age of the lunar maria? How do we know their ages?
-Mainly 4 to 2.5 billion years —some patches are less than 1 billion -We know because of the age of the basaltic rock, and also because it happened after the heavy cratering
What is the Moon's asthenosphere like?
-May extend to the center of the moon, or may be a thin shell surrounding a solid metallic core -partly molten rocks
What did the heat released during the accretion of the Moon do? What do you think the surface of the Moon looked like at this stage?
-May have completely melted outer several hundred kilometer of the moon, and created an ocean of molten rock. —It probably looked like a large ball of lava
How big were the differentiated parent bodies of most meteorites?
-Melting could only have occurred in larger bodies with diameter of hundreds of kilometers
Main components of planets?
-Metals, silicates, ices, and gases -Moons of outer planets are solid bodies with thick layers of water ice
What is the age of most meteorites? What does this tell us about the timing of condensation, accretion, and differentiation in the solar system? How then can we explain the few young meteorites with ages less than 1.5 billion years old?
-Most meteorites are about 4.6 billion years old —We use this time to establish the age of the solar system, marking the beginning of when solid material began to accumulate into sizable bodies —Accretion occurred soon after, and differentiated as they were heated from kinetic energy —1 billion years after the last volcanic rocks erupted on the moon —rare achondrites with distinctive features suggesting they were generated on Mars (crystallized from igneous magma) —Mineral and gas compositions define parent body - shows some meteorites actually came from larger planets
Where do meteorites come from? Is it possible that any of the meteoritic material that falls to Earth each year comes from asteroids? From other planets? Cite any evidence.
-Most of them come from the asteroid belt —rocks in solar orbits that cross Earths orbit (including comets) -Collisions within the asteroid belt or gravitational perturbation from much larger planets may gradually move small bodies from the asteroid belt to Earth. -Pieces of the Moon have been identified, and some possibly from Mars
How do lunar impact features larger than 300 km in diameter differ from those less than 300 km in diameter?
-Multiple rings (like a bullseye) -Spacing of rings increases outward -low ridges oriented radially to the basin -small domes or hummocks makes up the surface just within the outermost ring -steep cliff forms second ring -inner ring consists of a group of peaks that surround the plains in the middle of the basin -simple <20 km -terraces >20 km -central peaks >50 km -peak rings >200 km -multiring >300 km
Has the Moon's lithosphere experienced strong tectonic deformation? What is the evidence?
-Not during the last 2.5 billion years -We know because the network of young craters is not deformed -No evidence of intense folding or thrust faulting, and no indication of major rifts —Most of the major features are linear rilles and wrinkle ridges
What dramatic hypothesis for the origin of the Moon has emerged after the Apollo missions? What evidence supports this notion? What happened to the volatile materials during this event?
-One possibility is that the Earth was hit by a mars-sized object which ejected material into space, which accreted and became the moon. —some of Earths mantle vaporized in the process -The composition of the moon is similar to the Earths mantle, but poor in volatile materials -Moons core is very small
Explain how a geologic time scale was developed for events in the Moon's history.
-Radiometric dates determined from superposition and crater counts, crater degradation, and cross cutting relations. Based on craters Copernicus, imbrium, Eratosthenes, and nectaris. *not in exact years, only relative time period -absolute ages measured in earth based labs using radioactive elements
What do the mare basalts tell us about the interior of the Moon? About the thickness of the lithosphere?
-Shows there was still heat produced inside the moon, most likely through radioactive decay -The lithosphere is thick, as it was able to prohibit the complete isostatic compensation of the mare basalts.
Contrast the characteristics of silicates, metals, ices, and atmophile gases. Pay special attention to their melting points and densities.
-Silicates: rocky material made of aluminum, calcium, sodium, and potassium (solids less dense than metallic iron) -Metals: large group of elements that behaves like iron. Usually dense elements like iron, nickel, and cobalt -Ices: Materials that form low density solids only at low temperature. Mostly water, but also methane and nitrogen -Atmophile Gas: made up of hydrogen, helium, neon, carbon, and oxygen, which combine to form stable gases and make up the atmosphere of a planet
Under what conditions can solid rock flow? Would this allow differentiation to occur?
-Solid rock can flow when under high temperature and pressure. -This does help differentiation to occur, but it is largely dependent on critical temperature within the planet.
Discuss the characteristics and development of a planetary lithosphere.
-The Lithosphere consists of a solid outer shell, and is composed of a variety of rocks —Silicate minerals and ice prolly comprise over 95% of all lithospheres -It's development is strongly tied to the thermal history of the planet —If a planet formed hot, an early lithosphere would be thin and mobile, and fragments would slide about the slippery asthenosphere. As the planet cools, the lithosphere thickens and slowly becomes immobile. Lecture -Rigid outer part of a planet -Made of rocks -Solid planetary material -Mineral aggregates -Record of environment of formation
How thick is the Moon's lithosphere? How is its lithosphere different from its crust?
-The Moon's lithosphere is 1000 km thick -The lithosphere is composed of both the mantle AND the crust
For a planet like Earth, contrast the crust-mantle boundary with its asthenosphere-lithosphere boundary.
-The crust-mantle boundary goes from the surface of the planet all the way to the core -the asthenosphere-lithosphere boundary consists of the crust and upper mantle for the lithosphere, then down to the outer core for the asthenosphere
By what processes can a planet become hot? Why is it thought that almost all planets were hot when they formed?
-There are many different processes including: —accretionary heating: from impacts —core formation: frictional heating —radiogenic heating: radioactive elements give off heat —solar energy: gives off heat —T-Tauri heating: from this stage —tidal heating: proximity of satellite to primary planet (causes tugging that squishes planet when close, then reforms when distant) -All planets were hot when they formed because of accretionary heating, which is when two or more bodies collided and kinetic energy converted to thermal energy
The giant planets (Jupiter, Saturn, Uranus, and Neptune) have atmospheres much different than that of Earth. What are some of the important differences, and how did they form
-These planets have primary atmospheres of hydrogen and helium —atmospheres are thick and colorful -The inner planets may have had similar atmospheres, but the planets were to small to hold these atmospheres, so it was blown away during T-Tauri -Large quantities of uncondensable nebular gases surrounding the growing icy planets became hydrodynamically unstable and collapsed onto the planets core. Outer planets were big enough to hold their atmosphere during the T-Tauri phase.
How and why does the appearance of a lunar impact crater change with time?
-They change due to crater degradation —battering by countless impact events produces changes
If the Moon's crust formed from a magma ocean about 4.5 billion years ago, why are rocks that have radiometric dates this old so rare on the Moon?
-They erupted several hundred million years after the formation of the crust —May have formed as residual pockets of magma trapped beneath the thickening crust, and eventually broke through the surface.
What is the range of sizes of asteroids? Why are there so many small asteroids and so few large ones?
-They range from particles of dust to 1,000 km in diameter -There are more small asteroids because the asteroids often collide, and break up into small pieces.
How and under what conditions are the elements formed, and where are these conditions met?
-Through nuclear fusion in a star, elements up to iron are formed -Anything heavier than iron is formed during a supernova explosion
Contrast the behavior of volatile and refractory materials. Give an example of each.
-Volatile materials condense at very low temperatures —water, ammonia, methane, and nitrogen -Refractory materials form solids at very high temperatures —tungsten, osmium, zirconium
Describe how water is incorporated and then released from a planet's interior to create a hydrosphere? Why might some planets lack hydrospheres?
-Water starts in the mantle, then comes out to the surface through volcanism, when the gas cools, it falls to the earth to create a hydrosphere. -If planet cools, wet volcanic gas also cools —Rain or snow, seas, groundwater, ice caps, icy lithospheres -Some planets are so cold that the hydrosphere solidifies and becomes a cryosphere.
Under what conditions could a hydrosphere convert to a cryosphere? Where are such icy bodies in our solar system?
-When a planet cools so significantly that water cannot exist as a liquid -These are located on the icy satellites (moons) of the outer planets
When did the solar system originate? How can we date an event that happened so long ago?
-about 4.6 billion years ago -meteorites from asteroids are real samples of extraterrestrial life, and we can test them for age using radiometric ages. —by measuring the decaying radioactive isotopes such as uranium, potassium, and rubidium
What is an asteroid? Where are most of them found?
-asteroids are minor planets that are the fragmented remains of planetesimals that did not accrete to form a large planet. -most of them are found in the asteroid belt between Mars and Jupiter.
What are the major characteristics of stony meteorites?
-composed of iron and magnesium silicates -Chondrites: usually contain small spherules of silicate minerals about 1 mm in diameter. —Many are composed of olivine and pyroxene, and other minerals and glass at times -Achondrites: no condrules —composition and texture of many are very similar to basalt —achondrites are igneous rocks
How did it evolve from a diffuse nebula into a star with a surrounding hot disk of gas and dust?
-exact nature of how the collapse of diffuse dust and gas remains a mystery (gravity) -contraction of the cloud (happens when density reaches 20 atoms/cm3) causes more collisions among atoms, producing heat, elevating the temperature of the nebula —due to gradual warming, increased gas pressure causes collapsing cloud to slow down —once temperatures exceed 10,000 K, a protostar may begin to radiate light produced by release of gravitational and thermal energy -the gas cloud begins to rotate and collapse causes faster rotation, preventing a flattened disk of material from moving inward toward the protostar
What suggests that the plains of the maria are volcanic in origin? What type of rock are they made of?
-floods of lava fill large multi ring basins on near side of the moon —pictures were taken of individual flow fronts, and astronauts brought back rock samples -They are made of basaltic lava
Review the evolution of the orbits of the outer planets and explain the main tenets of the Nice model. How does this orbital reorganization affect the inner planets?
-giant planet orbits were affected by gravitational "nudges" from one another, and eventually, Jupiter and Saturn crossed, making their orbits more elliptical —This enlarged and tilted orbits of Uranus and Neptune and they scattered the remaining debris, sending some to the inner solar system —these meteorite impacts changed the spin axis and rotation of the inner planets
Why don't all of the planets rotate in the same direction? And why are some of the spin axes not vertical
-giant planet orbits were affected by gravitational "nudges" from one another, and eventually, Jupiter and Saturn crossed, making their orbits more elliptical —This enlarged and tilted orbits of Uranus and Neptune and they scattered the remaining debris, sending some to the inner solar system —these meteorite impacts changed the spin axis and rotation of the inner planets
What kinds of tectonic features accompanied the eruption of the mare basalts?
-graben and rille formation to compressive faulting and mare ridge formation
Why are cinder cones so rare on the Moon?
-lack of atmospheric drag on ejected particles and low gravitational attraction on the moon allows ejected particles to fly far from center of eruption —ejected material would tend to form a thin, low, widespread blanket of ash rather than a steep cinder cone
What is the origin of the Moon's wrinkle ridges?
-most were produced by compression
What is accretion, what is the origin of the materials the planets accreted out of, what happened to the left over material, and when did the planets in our solar system accrete?
-planetesimals only a few kilometers in diameter formed after condensing grains had settled due to gravity in the nebula -accretion is the event of theses planetesimals colliding and accumulating to form larger planetesimals -left over material was pushed away by the largest of the bodies, and eventually pushed to the outer solar system during the T-Tauro phase -believed to have happened about 3.9 billion years ago
What sources of heat may have been important in the thermal evolution of asteroids?
-short lived radioactivity (possibly drove off some volatiles) -accretion produces heat
Where in the solar system did large planets fail to completely accrete
-small particles in the Asteroid Belt and Kuiper Belt indicate these regions failed to completely accrete the material
How do the thickness and rigidity of the lithosphere of a planet respond to continued cooling?
-volcanism and tectonic evolution occur on the planet. —collisions and rifts driven by vigorous convection -numerous small plates, slabs or "rockbergs" form as melt cools -As the planet continues to cool, the lithosphere thickens further, eventually leading to a solid surface that doesn't move so easily. Lateral motion of separate sections of lithosphere is no longer possible
How are volcanoes a window on the interior of a planet?
-volcanism gives valuable insight on how a planet operates -volcanism shows the thermal history of a planet.
Outline the stages in the production of a crater by the impact of a meteorite.
1. Compression -kinetic energy moves through ground as shock wave -rock fractured, melted, and partly vaporized by shock metamorphism 2. Excavation -crater grows rapidly, attaining final diameter before material thrown from impact site reaches the ground -ejecta is blasted away, landing over the edge of the crater 3. Modification -floor of crater may rapidly rebound upward to compensate for material removed during excavation -slices of rock from steep walls may slip back into crater, forming terraces
Describe the general history and evolution of fusion reaction within a medium-sized star
1. In the beginning there was hydrogen (and some helium) 2. First stars are masses of H and He 3. Nuclear "burning" reactions in these stars -H to He -He to C 4. Expands outward and red giant forms 5. Outer shell rips off 6. Planetary nebula with remnant whit to black dwarf 7. Recharges space with newly formed He
Outline the stages in the evolution of a meteorite parent body.
1. Accretion of a planetesimal - an original body of primitive composition is formed 2. Planetesimal is heated by short-lived radio-activity to the point of mild metamorphism, driving off some volatiles -Could be heated to the melting point of metallic iron. Dense segregation of iron drains toward the center of the body to form a core or several small accumulations of metal 3. If heating is intense enough, silicates in chondrites interior may melt to produce magma, which erupts at the surface to produce a thin veneer of lava and associated intrusive rocks. Eventually, the asteroid cools as heat is radiated away into space; the core and mantle become solid. Depending on size, composition, and distance from the Sun, for a specific asteroid this differentiation process may have ended at any point of the evolutionary scheme 4. Fragmentation of such bodies could then produce the spectrum of observed asteroid and meteorite types. -A variety of types could come from one body; most asteroids were not heated beyond the first or second step, and only a very few have exposed metallic cores stripped of their silicate cloaks.
Put the major periods of the Moon's history in order from oldest to youngest.
1. Birth of the Moon 2. Pre-Nectarian Period 3. Nectarina Period 4. Imbrian Period 5. Erathosthenian Period 6. Copernican Period
Describe the events of the Big Bang
1. Inflation @ 10^-44 seconds 2. Quark Soup @ 10^-12 seconds 3. Neutrons and Protons form @ 10^-5 seconds 4. Nuclei form @ 1-100 seconds 5. Matter and Radiation decouple @ 400,000 years 6. First galaxies and stars at .6 to 1 billion years 7. Modern Universe @ 14 billion years
How are lunar craters modified as time passes?
1. Later impacts may partly or completely destroy older crater 2. Crater may be covered with ejecta from younger crater 3. Crater may be partially or completely buried by lava flows or sedimentary deposits 4. Geologic activity of atmosphere and hydrosphere of planet may erode the crater 5. Cratering my undergo tectonic modification by faulting or folding
After the formation of the multiring basins, what were the next major events in lunar history?
After the formation of the multiring basins, there was an extrusion of mare basalts, and later a light meteorite bombardment.
What is an atom, and what are its major constituents?
An atom is what makes up matter. It's major constituents are protons, neutrons, and electrons.
Explain why the rocks found at the surface of a planet, say the Moon, are so different in elemental composition from the meteoritic material from which the planet formed.
Because of differentiation. This happens because elements have distinctive physical properties (mostly density) and chemical affinities, which allow them to separate from one another.
What are the main reasons that the Moon is different from these small bodies?
Because of its size and gravitational pull
How does a medium-sized star die?
By turning into a planetary nebula (expands outward and red giant forms. Hydrogen-burning gradually proceeds to the surface ripping the surface layers away to form a planetary nebula)
If a planet begins hot, what process dominates the rest of its thermal history?
Cooling - heat is constantly given off
What geologic processes have dominated the last 3 billion years of the Moon's history?
Cooling and contracting of the planet
What are the major features related to lithospheric extension? To lithospheric compression?
Extension -Stretching and fracturing of shallow lithosphere -May fracture to form high-angle faults along which movement of blocks occurs -Rifts and grabens, fault-bounded valleys. Compression -lithosphere may buckle and fold, or break into thin sheets bounded by low-angle faults (thrust faults) -usually form sinuous, overlapping ridges
What are the principal features of an impact crater? Contrast the origin and features of an impact crater with one produced by volcanic activity.
Impact Crater -typically circular -deformed rim -ejecta blanket thrown out of crater -lens shaped deposit of fragmented rock and small amounts of lava produced by shock melting -highly fractured bedrock Volcanic Crater -typically asymmetrical or elongate -material is transported and deposited to form a new rock body/landform
Compare and contrast inner and outer planets
Inner planets -metallic core -silicate rock surface Outer planets -probably a small rocky or icy core -no solid surface -deep atmosphere that thickens downward into hot liquid -rings of small particles
Where does the energy for crater excavation, rock fracturing, and melting come from?
It comes from the kinetic energy of the impacting meteor. The meteor hits and makes a compressional wave, that is reflected as a rarefaction wave.
What causes tectonic deformation of a planet's surface?
It is caused by deformation of a planet's outer layers arising from forces inside the planet. -Extension and compression
What is a star
Large and capable of generating energy through nuclear fusion
What are the major tectonic features on the Moon?
Linear rilles and wrinkle ridges
How did linear rilles form, by extension or compression?
Linear rilles formed by extension
What style of volcanism produces basaltic plains?
Low shield volcanoes
What kinds of volcanic landforms are found on the Moon?
Lunar Maria, volcanic rocks, volcanic shields, and fissures
What are the major differences between the highlands and maria on the Moon? How do they differ in surface features? In composition? In geologic history?
Maria -dark and smooth, with only a few craters -some occur within walls of large circular basins (Crisium, Serenitatis, and Imbrium) -vast layers of thin basaltic lava, which flowed into depressions -about 5 km below moon mean radius -formed by extrusion of vast amounts of lava that accumulated in lowlands of large craters or basins, and in some cases overflowed and spread onto highlands Terrae (80% of moon) -Constitute about 2/3 of near side of the moon -highest and most rugged topography on the moon -contains abundant craters (50 to 1000 km in diameter) -possibly as much as 5 km above moon mean radius -light silicate minerals accumulated at top of magma ocean, formed crust, then got meteorized
What is an asteroid
Mark transition between rocky inner planets and gaseous outer ones, can be rocky, lava, metallic, or water ice
What prevented Mars from obtaining an ice-rich outer shell encasing a rocky interior as the temperature of the nebula continued to drop?
Mars is still close enough to the sun that only silicates and metals could condense. It was too hot for ices to condense during its formation. -temperatures below 400K allow condensation of sulfates, carbonates, and hydrated silicates, but Mars is above 400K
Describe the internal structure of a planet in terms of mechanical properties and then in terms of chemical properties.
Mechanical Properties -Lithosphere: mechanically rigid, strong cool outer layer of solid planet -Asthenosphere: Mechanically weak, Partially molten, lies beneath lithosphere -Mesosphere: Solid rock -Outer Core: liquid -Inner Core: solid Chemical Properties -Crust: Silicates -Mantle: Silicates (silicon and oxygen with iron and magnesium) -Core: Iron (and nickel)
Compare the typical lifetime (in years) of a medium-sized star like our Sun and a large star (~10 times bigger)
Medium sized star lasts about 10 billion years till it becomes a red giant, while a large stars last only millions of years
Explain two ideas for the origin of multiring basins.
Mega terrace Model -postulates that the outer rings of a multi ring basin are the margins of huge terraces that slumped downward along steep faults -one of the inner rings marks the rim crest and innermost ring is formed by same process that forms peak rings in smaller craters Nested Crater Model -proposes that outer ring of the crater is the actual rim crest or limit of excavation for the crater. -inner rings of basins are produced as shock waves encounter changes in layered structure of planet's surface in similar way as discussed earlier for production of small flat-floored craters -deep crater rebounds to surface, and minor slumping of material off rings may occur.
What is the order of planets?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto
Are all meteorites alike? What are the major categories?
No they are not all the same. The major categories are stony, stony-iron, and iron.
How do the Sun and other stars derive their energy?
Nuclear Fusion: Intense heat from the sun fuses elemental atoms together to form new elements
Comet
Occupy the Oort cloud, small balls of ice that go into and out of the solar system
What happens to the elements blown away into interstellar space?
Recharges space with newly formed He
What is the sequence of changes that accompanies the increase in crater size?
Size and shape depend on energy
What happens to a hot gas as it slowly cools?
Solids begin to condense as the gas cools
What is a planet
Spherical object that orbits a central luminous star, and are large enough to have cleared out their orbit
What is the most common type of meteorite to fall to Earth?
Stony meteorites
What is the major difference in the landforms on the near side of the Moon compared with those on the far side of the Moon?
The near side of the moon has a mix of Maria and terrae, but the far side of the moon is mostly cratered terrae, with little Maria.
Why don't Earth and other small planets have thick atmospheres of hydrogen and helium? After all, these are the two most abundant elements in the universe and in the solar nebula from which the planets are presumed to have formed.
The inner planets are too small to hold an atmosphere of hydrogen and helium. They may have had atmospheres of hydrogen and helium at some point, but it was likely blown away during the T-Tauri phase
Why are there fewer craters on the lunar maria than on the highlands?
The lunar Maria are younger than the highlands (4.6 billion years vs. 4 billion) so it missed out on the meteor showers that formed the highlands. Also the Maria flowed out over the surface after it was impacted, so it smoothed over many craters.
Why is the present-day Moon less dynamic than Earth?
The rigid layer (lithosphere) is too thick to allow the extrusion of lava. The moon continues to cool, and as it does it becomes even less active
Did linear rilles or wrinkle ridges continue to form longer on the Moon?
The wrinkle ridges, because they form as the moon is contracting due to cooling
What is the fate of elements newly created in a massive star?
They are ejected into space where they may be recycled into new planets, stars
Contrast differentiated and undifferentiated meteorites.
Undifferentiated -have not undergone any process, like melting, that segregates elements because of their chemical affinities or properties Differentiated -has segregated into layers
What marks the death of a large star?
With multiple layers of fusion, large stars evolve rapidly and explode to form supernovas. Elements heavier than iron are produced in the cataclysm
