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62 Cards in this Set

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What are the major patterns of motion in our solar system?
All planets orbit the Sun in the same direction and with nearly circular orbits in nearly the same plane. The Sun and most planets rotate in the same direction that they orbit. Most large moons orbit their planets in the same direction as well.
What are the two major types of planets?
The two major types of planets are the small, rocky terrestrial planets and the large, hydrogen-rich jovian planets.
Where do we find asteroids and comets in our solar system?
Most asteroids reside in the asteroid belt between Mars and Jupiter. Comets are found in two main regions: the Kuiper belt, which begins near the orbit of Neptune, and the much more distant Oort cloud.
Where are a few important exceptions to these general rules?
Uranus and Pluto rotate sideways compared to their orbits. Venus rotates "backward". Triton orbits Neptune backward from what we'd expect. Earth has a surprisingly large Moon
How does the Sun influence the planets?
Its gravity governs planetary orbits, its heat is the primary influence on planetary surfaces temperatures, it is the source of virtually all the visible light in our solar system, and high-energy particles from the Sun influence planetary atmospheres and magnetic fields.
What do you find particularly interesting about each planet?
Mercury has extreme days and nights, tall steep cliffs, and large iron content.
Venus has an extreme greenhouse effect.
Mars shows evidence of a past wet era.
Jupiter has a hydrogen and helium atmosphere and many moons.
Saturn has rings and a moon, Titan, that is larger than mercury.
Uranus and its moons make up a system tipped on its side compared to toehr planets.
Neptune's largest moon, Triton, has nitrogen "geysers" and a "backward" orbit.
What are four major categories of spacecraft missions?
flybys, orbiters, landers, probes, sample return missions
What four charcteristics of our solar system must be explained by any formation theory?
patterns of motions, differences between terrestrial and jovian planets, the presence of asteroids and comets, and exceptions to the rules.
What is the basic idea behind the nebular theory?
Our solar system formed from a giant cloud of gas and dust, with the Sun forming at the center of the cloud and the planets forming the spinning, flattened disk of material that orbited the young Sun.
solar nebula
the interstellar cloud from which our solar system was born
how did gravitational collapse affect the solar nebula?
the nebula heated up, spun fater, and flattened into a disk
What produced the orderly motion we observe in the solar system today?
The orderly motion of the solar system reflects the original motion of the spinning disk of the solar nebula. The plane of this disk became the plane in which the planets now orbit the Sun, and the direction of the disk's spin became the direction of the planetary orbits.
What key fact explains why there are two types of planets?
Nearer to the Sun the frost line, temperature were so high that only metal and rock could condense into solid particles. Beyond the frost line, cooler temperatures allowed hydrogen compounds to condense into solid particles of ice. Thus, the solid material beyond the frost line included abundant ice in addition to rock and metal.
How did the terrestrial planets form?
terrestrial planets formed inside the frost line from condensation of solid grains of metal and rock that accreted into planetesimals which grew into planets.
How did the jovian planets form?
Jovian planets formed beyond the frost line from condensation of solid grains of metal rock and lots of ice that accreted into icy planetesimals. The capture of hydrogen and helium gas by the largest icy planetesimals made "miniature solar nebulae." The jovian planets formed at the centers of those nebulae, while moons accreted from ice in the spinning disks.
a planet must be
a.) in orbit around sun (star)
b.) nearly round b/c of gravity
c.) has cleared out neighborhood around orbit
dwarf planet
not a moon, not cleared its neighborhood
densities of planets
average densities of planets are determined by planet radius, orbital period, and orbital semimajor axis of moon
gravity regulates orbit of planets, heat determines temp of planets, provides practically all visible light in SS, high energy particles streaming out from sun influence planetary atmosphere and magnetic fields. 99.9 % of ss mass. converts 4 million tons of mass into energy each second
no atmosphere that would circulate heat, no greenhouse effect: long day: very hot and cold: big difference between night and day. made of metal and rock; large iron core
extremely hot due to greenhouse effect of atmosphere. still has active geology.
volcanism and tectonics on venus
impact craters are evenly spread over venusian surface, which implies planet's entire surface is same age.
lack of weather: explained by
surface of venus is very hot, so it is too hot for liquid or ice to exit
venus rotates slowly and backward so little wind is generated
how are asteroids and comets related to the planetesimals that formed the planets?
Asteroids are leftover planetesimals of the inner solar system, and comets are leftovers of the outer solar system.
heavy bombardment
period early in ss's history during which planets were bomborded by many left-over planetesimals
how do we explain the exceptions to the rules?
collisions or close encounteres with leftover planetesimals can explain the exceptions
how do we think our moon formed?
A mars-size leftover planetesimal slammed into earth, blasting rock from earth's outer layers into orbit, where it reaccreted to form the Moon.
how old is SS
4.6 billion years old, an age we determine from radiometric dating of the oldest meteorites.
radiometric dating
looking for radioactive isotopes and their decay products within the rock. by comparing present-day amounts of an isotope and its decay product, we can determine how much of the isotope must have been present when teh rock solidified. we can then use the half-life of the isotope to determine how long it has been undergoing decay within the rock, which tells us the rock's age
roche limit
close to planets there is a region where tidal forces are so strong moon will be ripped apart and become rings
cold, low-density atmosphere that provides essentially no greenhouse effect
jupiter's moons
io: active volcanoes all over, yellow because of sulfur compounds
europa: possible subsurface ocean
ganymede: largest moon in ss
callisto: large cratered "ice ball"
saturn's rings
made of countless small chucks of ice and rock, each orbiting saturn like a tiny moon. outer rings have longer period b/c of Kepler's laws
nebular theory again
solar system formed from giant cold cloud of gas and dust which collapsed into a smaller rotating disk. depends on 2 principles: gravity and conservation of angular momentum.
nebular theory trois!
ss formed out of protostellar cloud (cloud of gas from whcih our own ss formed) which collapses under its own gravity. we have observational evidence that is we observe stars in the process of forming today, and they are always found within interstellar cloud of gas. stars form from collapse of protostellar gas clouds.
the gravitational collapse
solar protostellar cloud was very cold, rotating slightly.
then the shock wave from a nearby supernova, maybe, may have made the cloud collapse under own gravity.
as radius decreased, it rotated faster, forming a disk (conservation of angular momentum)
as cloud fell onto protostar and disk, gravitational p.e. was converted to heat (conservation of energy)
flattening of solar nebula
as cloud collapses, clumps of gas collide and merge. their random velocities average out into cloud's direction of rotation. spinning nebula assumes shape of disk.
orderly motions in the ss
the sun formed in the very center of the nebula. planets formed in the rest of the disk. this explains that:
all planets lie along one plane, orbit in one direction (spin direction of disk), the sun rotates same direction, planets would tend to rotate this same direction, most moons orbit in this direction, and most planetary orbits are near circular (collisions in disk)
rocks collided and made ga; ices (h rick gas compounds) began to condense (i.e.solidify) out of the nebula...depending on temperature.
hydrogen compounds (ices) condensed beyond the frost line
small grains stick to one another via electromagnetic force until they are massive enough to attract via gravity to form planetesimals which will:
combine near the sun to form rocky planets
combine beyond frostline to form icy planetesimals which
capture H/He far from sun to form gas planets
origin of asteroids
something cleared leftover gas, but not leftover planetesimals. leftover rocky planestimals which did not accrete into a planet: inhabit the asteroid belt btwn Mars and Jupiter (Jupiter's gravity prevented a planet from forming there)
heavy bombardment
heavy bombardment is the first few hundred million years after the planets formed, which is when most impact craters were formed.
it explains why some moons oribt opposite their planets rotation (capture moons like triton)
why rotation axes of some planets are tilted (impacts knock them over, like Uranus)
why some planets rotate more quickly than others (impacts 'spin them up')
why earth is only terrestrial planet w/ large moon (giant impact)
formation of moon
earth was struck by a mars-sized planetesimal, part of earth's mantle was ejected, with coalesced in the moon. it orbits in same direction as earth rotates, it has lower density than earth, earth was "spun up", and moon is large relative to earth, in comparison w/ other terrestrial planets
so, recipe for planets
gravity+angular momentum--> make rotating disk
dust settles, coagulates--> make larger bodies
gravity make many "tiny planets"
planetesimals collide w/ each other b/c multi-body system is unstable, chaotic
slower growth--> make small (terrestrial planets)
faster growth plus gas --> make giant planets
outcomes are highly variable
its gravity governs the orbits of the planets. its heat is the primary influence on planetary temperatures, and it is the source of virtually all the visible light in our ss--the moon and planets shine only by virtue of the sunlight they reflect. high-energy particles flowing outward from the sun (solar wind) help shape the magnetic fields of the planets and can influence planetary atmospheres.
outer layer of relatively rigid rock
encompasses the crust and part of the upper mantle
earth and venus have thin ones and mars mercury and moon include most or all of mantles
how interiors get hot
heat of accretion: heat generated at the time the planets accreted from planetesimals.
heat from differentiaation: heat generated at the time the planets differentiated into their core-mantle-crust structures.
heat from radioactive decay: heat generated as radioactive nuclei in the planetary interior undergo natural decay.
process in which hot material expands and rises while cooler material contracts and falls.
the process by which thermal energy is transferred by direct contact from warm material to cooler material.
three requirements for global magnetic field
an interior region of electrically conducting fluid (liquid or gas) such as molten metal.
convection in that layer of fluid.
at least moderately rapid rotation.
4 geological processes that affect planets surfaces
impact cratering, volcanism, tectonics, and erosion
impact cratering
the blasting of bowl-shaped impact craters by asteroids or comets striking a planet's surface.
the eruption of molten rock, or lava, from a planet's interior onto its surface.
tthe disruption of a planet's surface by internal stresses
the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
requirements for erosion
planetary size: a terrestrial world can have an atmosphere only if it has had significant outgassing (volcanism requires internal heat and therefore bigger planets). size determines strength of gravity, and atmospheric gases are more easily lost to space on worlds with weaker gravity.
distance from sun: affects whether gas can remain in atmosphere. higher temperatures on a world closer to the sun will make it easier for atmospheric gases to escape. colder temperatures on a world farther from the sun may cause atmospheric gases to freeze out.
rotation rate: faster rotation mean stronger winds and storm.
why is earth the only terrestrial world with a strong magnetic field?
a planetary magnetic field requires three things: an interior layer of electrically conducting fluid, convection of that fluid, and rapid rotation.
how are the geological processes connected to fundamental planetary properties?
impacts affect all planets similarly, but larger planets are more likely to have their impact craters erased by other geological processes. volcanism and tectonics require interior heat, which is retained only by larger planets. erosion can occur only on planets with substantial atmospheres. this requires large size to allow outgassing to make an atmosphere, moderate distance from the sun to prevent the gas from escaping or freezing, and wind or rain. wind can occur only with moderately fast rotation.
coriolis effect
moving objects veer right on a surface rotating counterclockwise, moving objects veer left on a surface rotating clockwise
four major facts which affect long-term climate
reflectivity: cloudiness (smog, dust) will reflect light away from earth to cool us off
tilt: greater tilt makes more extreme seasons, smaller tilt keeps polar regions colder and darker
sunlight: sun is getting slowly brighter with time, brighter sunlight increases planetary surface temperatures.
greenhouse gases: an increasure in gases will warm the planet
sources of atmospheric gas
outgassing: release of gas trapped in interior rock by volcanism.
evaporation/sublimation: surface liquids or ices turn to gas when heated.
bombardment: micrometeorites, solar wind particles, or high-energy photons blast atoms/molecules out of surface rock.
ways to lose atmospheric gas
condensation: gas turns into liquids or ices on the surface when cooled. (mars used to be warmer as it got colder co2 froze, lost atmosphere.
chemical reactions: gas is bound into surface rocks or liquids
stripping: gas is knowcked out of the upper atmosphere by solar wind particles
impacts: a comet/asteroid collision with a planet can blast atmospheric gas into space.
thermal escape: lightweight gas molecules are lost to space when they achieve escape velocity.
las three permanent top two part of a cycle
greenhouse effect
planetary warming caused by the absorption of infrared light from a planet's surface by greenhouse gases such as carbon dioxide, methane, and water vapor