PHYS 107 ASTRO FLASH CARDS

Which of the following observations indicates that conditions on Mars may have been suitable for life in the past?	There are dried-up riverbeds on Mars
Which of the following is not a characteristic of the outer planets?	They have very few, if any, satellites.
Pluto is different from the other outer planets in all of the following ways except which one?	Its surface temperature is very cold
What is the primary reason why a Pluto flyby mission would be cheaper than a Pluto orbiter?	The fuel needed for an orbiter to slow down when it reaches Pluto adds a lot of weight to the spacecraft
The most metal rich terrestrial planet is	Mercury
Which planet, other than the earth, has visible water ice on it?	Mars
Based on the frequency with which we see comets from Earth, astronomers estimate the total number of comets in the solar system to be	1 trillion.
The planet closest in size to Earth is	Venus
What is aerobraking?	the technique of using a planetary atmosphere to change the orbit of a spacecraft
Which of the following is not a characteristic of the inner planets?	They all have substantial atmospheres
Which planet has the highest average surface temperature, and why?	Venus, because of its dense carbon dioxide atmosphere
Which of the following is not an advantage of spacecraft flybys over ground based telescope observations?	spacecraft can monitor changes in a planet's atmosphere over long times
Some astronomers suggest that, rather than being a planet, Pluto is really just a large member of	the Kuiper belt
Where does nuclear fusion occur in the Sun?	in its core
Which of the following is furthest from the Sun?	a comet in the Oort cloud
Where are most of the known asteroids found?	between the orbits of Mars and Jupiter
Which is the densest planet in the solar system?	Earth
How does the Sun's mass compare with that of the planets?	It is a thousand times more massive than all the planets combined.
What are the main constituents of the jovian planets?	hydrogen and helium
Which of the following statements is not an observed pattern of motion in our solar system?	Most planets orbit at the same speed.
Which of the following is not an exception to the general patterns of motion in the solar system?	the rings of Saturn
Which of the following is not an exception to the general patterns of motion in the solar system?	the rings of Saturn
All the planets in the solar system have at least one moon	False
Why are the inner planets made of denser materials than the outer planets?	In the inner part of the nebula only metals and rocks were able to condense because of the high temperatures, whereas hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions.
According to the nebular theory, how did the Kuiper belt form?	It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet
Which of the following has not been detected around other stars in the Galaxy?	terrestrial planets
What is the most likely reason that there are no giant planets beyond Neptune?	By the time planetesimals grew to a large enough mass to hold onto an atmosphere, the solar nebula had been blown away.
The heavy bombardment phase of the solar system lasted	several hundreds of millions of years
What happened during the accretion phase of the early solar system?	Particles grew by colliding and sticking together
Which of the following are relatively unchanged fragments from the early period of planet building in the solar system?	all of the above
According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets?	Most of the exceptions are the result of giant impacts
Which of the following is the origin of almost all the large moons around the jovian planets?	They were formed by condensation and accretion in a disk of gas around the planet
According to our theory of solar system formation, what is Pluto?	Pluto is the largest of the Kuiper-belt comets
The age of our solar system is approximately	4.6 billion years.
Why did the solar nebula flatten into a disk?	It flattened as a natural consequence of collisions between particles in the nebula, changing random motions into more orderly ones
Which of the following lists the ingredients of the solar nebula from highest to lowest percentage of mass of the nebula?	light gases (H, He), hydrogen compounds (H2O, CH4, NH3), rocks, metals
Where did the elements heavier than hydrogen and helium come from?	They were produced inside stars
Which of the following puzzles in the solar system cannot be explained by a giant impact event?	the orbit of Triton in the opposite direction to Neptune's rotation
Based on our current theory of the earth's formation, the water we drink comes from	comets that impacted the earth
At first, the Sun's present-day rotation seems to contradict the prediction of the nebular theory because	the theory predicts that the Sun should have been rotating fast when it formed, but the actual rotation is fairly slow.
Suppose you find a rock that contains some potassium-40 (half-life of 1.3 billion years). You measure the amount and determine that there are 5 grams of potassium-40 in the rock. By measuring the amount of its decay product (argon-40) present in the rock, you realize that there must have been 40 grams of potassium-40 when the rock solidified. How old is the rock?	3.9 billion years
What percentage of the solar nebula's mass consisted of hydrogen and helium gases?	98 percent
The nebular theory of the formation of the solar system successfully predicts all but one of the following. Which one does the theory not predict?	the equal number of terrestrial and jovian planets (with the exception of Pluto)
The age of the solar system can be established by radioactive dating of	the oldest meteorites
According to our theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?	The laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk.
Steep-sided stratovolcanoes are made from lava that	has a high viscosity
Which of the following describes impact cratering?	the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
Mineral evidence shows that Earth's oceans have existed for	over four billion years
Spacecraft have landed on all the terrestrial worlds except	Mercury
Which of the following has virtually no effect on the structure of a planet	its magnetic field
Which internal energy source is the most important in continuing to heat the terrestrial planets today?	radioactivity
Which of the following does not have a major effect in shaping planetary surfaces?	magnetism
The core, mantle, and crust of a planet are defined by differences in their	composition
Which of the following show evidence of ancient river beds?	Mars
Which two properties are most important in determining the surface temperature of a planet?	distance from the Sun and atmosphere
What kind of surface features may result from tectonics?	all of the above
Which of the following describes erosion?	the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
The main process by which heat flows upward through the lithosphere is	conduction
Heat escapes from the planet's surface into space by thermal radiation. Planets radiate almost entirely in the wavelength range of the	infrared
Shallow-sloped shield volcanoes are made from lava that	has a medium viscosity
What type of stresses broke the earth's lithosphere into plates?	the circulation of convection cells in the mantle, which dragged against the lithosphere
How large is an impact crater compared to the size of the impactor?	10 times larger
Which of the following worlds have the thinnest lithospheres?	Earth and Venus
Some of the oldest continental crust on Earth lies in	Northeastern Canada
How fast do plates move on the earth?	a few centimeters per year
How have we been able to construct detailed maps of surface features on Venus?	by using radar from spacecraft that were sent to orbit Venus
When we see a region of a planet that is not as heavily cratered as other regions, we conclude that	the surface in the region is younger than the surface in more heavily cratered regions
What are the circumstances under which convection can occur in a substance?	when the substance is strongly heated from underneath
Which of the terrestrial worlds has the strongest magnetic field?	Earth
Which of the following does not provide evidence that Mars once had flowing water?	the presence of vast canals discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell
The relatively few craters that we see within the lunar maria	were formed by impacts that occurred after those that formed most of the craters in the lunar highlands
How long, approximately, do geologists estimate it takes for the entire seafloor to be replaced due to continental drift?	200 million years
Why is continental crust lower in density than seafloor crust?	Continental crust is made from remelted seafloor crust and therefore only the lower-density material rises to form it.
Under what circumstances can differentiation occur in a planet?	The planet must have a molten interior
The polar caps on Mars are composed of	mostly solid carbon dioxide and some water ice
Why are there fewer large craters on the seafloor than on the continents?	The seafloor crust is younger than the continental crust.
When we say that a liquid has a high viscosity, we mean that it	flows slowly like honey
A planet is most likely to have tectonic activity if it has	high internal temperature.
What is differentiation in planetary geology?	the process by which gravity separates materials according to density
Valles Marineris is a(n)	large canyon on Mars
How does seafloor crust differ from continental crust?	Seafloor crust is thinner, younger, and higher in density.
Which of the following describes volcanism?	the eruption of molten rock from a planet's interior to its surface
What drives the motion of the continental plates on Earth?	convection cells in the mantle
Ridges in the middle of the ocean are places where	hot mantle material rises upward and spreads sideways, pushing the plates apart
Which two geological processes appear to have been most important in shaping the present surface of Venus?	volcanoes and tectonics
The Caloris Basin on Mercury covers a large region of the planet, but few smaller craters have formed on top of it. From this we conclude that	the Caloris Basin formed toward the end of the solar system's period of heavy bombardment
Which of the following is not evidence for continental drift on Earth?	the paucity of impact craters
The geysers and hot springs of Yellowstone National Park result from	plumes of hot mantle rising in a hot spot within a plate
Which internal energy source produces heat by converting gravitational potential energy into thermal energy?	both A and B
What process has shaped Earth's surface more than any other?	plate tectonics
What is the most important factor that determines the thickness, and therefore strength, of the lithosphere?	internal temperature
The three principal sources of the internal heat of terrestrial planets are	accretion, differentiation, and radioactivity
Which of the following best describes convection?	It is the process in which warm material expands and rises while cool material contracts and falls.
Which of the following regions was the result of plumes of hot mantle rising in a hot spot within a plate?	the islands of Hawaii
What are the conditions necessary for a terrestrial planet to have a strong magnetic field?	both a molten metallic core and reasonably fast rotation
What is the most important factor that determines the thickness, and therefore strength, of the lithosphere?	internal temperature
The three principal sources of the internal heat of terrestrial planets are	accretion, differentiation, and radioactivity
Which of the following best describes convection?	It is the process in which warm material expands and rises while cool material contracts and falls.
Which of the following regions was the result of plumes of hot mantle rising in a hot spot within a plate?	the islands of Hawaii
What are the conditions necessary for a terrestrial planet to have a strong magnetic field?	both a molten metallic core and reasonably fast rotation
Why does Titan have such a nitrogen-rich atmosphere?	The nitrogen comes from the breakup of ammonia (NH3) by solar radiation and subsequent thermal escape of the hydrogen
Why do jovian planets bulge around the equator, that is, have a "squashed" appearance?	Their rapid rotation flings the mass near the equator outward.`
Why is Saturn almost as big as Jupiter, despite its smaller mass?	Jupiter's greater mass compresses it more, thus increasing its density.
Which moon has the most substantial atmosphere?	Titan
Which of the following does not yield information on jovian planet interiors?	spectroscopy of the cloud layers
How much energy does Jupiter emit compared with how much it receives from the Sun?	It emits twice as much
The four Galilean moons around Jupiter	a mixture of rock and ice, with the ice fraction increasing with distance from Jupiter.
What is the most important reason why an icy moon is more likely to be geologically active than a rocky moon of the same size?	Ice has a lower melting point than rock.
Which previously unknown planet's location was predicted from mathematical calculations of orbital motions?	Neptune
Why is Neptune denser than Saturn?	It has a different composition than Saturn, including a higher proportion of hydrogen compounds and rocks
Which of the following is not due to tidal forces?	the retrograde orbit of Triton (a moon of Neptune)
Why are there no impact craters on the surface of Io?	Io did have impact craters but they have all been buried in lava flows.
Why do Uranus and Neptune have blue methane clouds but Jupiter and Saturn do not?	Methane does not condense into ice in the warmer atmospheric temperatures of Jupiter and Saturn
What are the spokes in Saturn's rings?	particles of dust suspended above the rings by magnetic forces
Why is Jupiter denser than Saturn?	The extra mass of Jupiter compresses its interior to a greater extent than that of Saturn
Why do astronomers think Miranda has such an unusual surface?	It underwent an episode of tidal heating in the past
Which of the following planets cannot be seen with the naked eye?	Neptune
What is the Cassini division of Saturn's rings?	a large gap, visible from Earth, produced by an orbital resonance with the moon Mimas
What mechanism is most responsible for generating the internal heat of Io that drives the volcanic activity?	tidal heating
How do astronomers think Saturn generates its internal heat?	by raining dense helium droplets from higher to lower altitudes, resembling the process of differentiation
The fact that most moons always show the same face to their planet is	a natural consequence of tidal forces acting on the moons.
Which of the following statements about Titan is not true?	It is the coldest moon in the solar system
The belts and zones of Jupiter are	alternating bands of rising and falling air at different latitudes
What is Jupiter's Great Red Spot?	a long-lived, high-pressure storm
How do the jovian planet interiors differ?	All have cores of about the same mass, but differ in the amount of surrounding hydrogen and helium
How thick are Saturn's rings from top to bottom?	a few tens of meters
What is differential rotation?	when a body rotates faster or slower at its equator than it does at its poles
Why do astronomers believe Triton may have been a planet that was captured by Neptune?	It orbits Neptune in the opposite direction of Neptune's rotation
Why are Saturn's rings so thin?	Any particle in the ring with an orbital tilt would collide with other ring particles, flattening its orbit.
Which of the following statements about the rings of the four jovian planets is not true?	All probably look much like they did when the solar system first formed.
Why do the jovian planet interiors differ?	Accretion took longer further from the Sun, so the more distant planets formed their cores later and captured less gas from the solar nebula than the closer jovian planets.
What causes synchronous rotation?	A massive planet exerts a tidal force on a moon that causes the moon to align itself such that its tidal bulges always point toward and away from the planet.
Hydrogen exists as a gas, liquid, and solid within Jupiter.	True
Both the existence and the location of Neptune were predicted mathematically before the planet actually was detected by telescope.	True
Pluto exerts a noticeable gravitational influence on Uranus.	False
Jupiter does not have seasons because it has no appreciable axis tilt.	True
Some of the moons of the jovian planets have significant atmospheres.	True
Jupiter is slowly shrinking through gravitational contraction today.	True
Jupiter's Great Red Spot is a low-pressure storm like a hurricane on Earth.	False
The densities of the Galilean moons increase with distance from Jupiter, just as the densities of the planets increase with distance from the Sun.	False
If Jupiter were 10 times more massive, it would actually have a smaller radius.	True
Uranus continues to generate internal heat through gravitational contraction.	False
Synchronous rotation is when a moon's rotation period and orbital period are the same.	True
Why does the plasma tail of a comet always point away from the Sun?	The solar wind blows the ions directly away from the Sun.
When do comets generally begin to form a tail?	inside of Jupiter's orbit
Which is closest to the average distance between asteroids in the asteroid belt?	1 million km
Why do we sometimes observe asteroids at the distances of the gaps in the asteroid belt?	A gap is located at an average orbital distance, and asteroid orbits often have large eccentri
A typical shooting star in a meteor shower is caused by a ________ entering the earth's atmosphere.	pea-size particle from a comet
If we know the size of an asteroid, we can determine its density by	determining its mass from its gravitational pull on a spacecraft, satellite, or planet.
Why isn't there a planet where the asteroid belt is located?	Gravitational tugs from Jupiter prevented material from collecting together to form a planet.
What is Charon?	Pluto's moon
How does the largest asteroid, Ceres, compare in size to other solar system worlds?	It is about half the size of Pluto.
Comets with extremely elliptical orbits, like comets Hyakutake and Hale-Bopp,	come from the Oort cloud.
Where are the Trojan asteroids located?	along Jupiter's orbit, 60° ahead of and behind Jupiter
When was Pluto discovered?	about 70 years ago
Why do asteroids and comets differ in composition?	Asteroids formed inside the frost line, while comets formed outside.
Processed meteorites with high metal content probably are	chunks of a larger asteroid that was shattered by a collision
Which of the following statements about comets and asteroids is true?	Comets are balls of ice and dust
What is a meteorite?	a fragment of an asteroid from the solar system that has fallen to the earth's surface
On average, how often do impactors about 10 km in size, large enough to produce mass extinction, hit the earth?	once every hundred million years
In the asteroid impact theory of the extinction of the dinosaurs some 65 million years ago, the dinosaurs (and over half of all the other species on the earth at that time) died off largely because	dust injected into the stratosphere from the impact absorbed visible light from the Sun, causing global temperatures to plummet.
Where did comets that are now in the Kuiper belt originally form?	near the radius at which they orbit today
The large gaps in the asteroid belt (often called Kirkwood gaps) are caused by	orbital resonances with Jupiter
What part of a comet points most directly away from the Sun?	the plasma tail
What do asteroids and comets have in common?	Most are unchanged since their formation in the solar nebula.
Most meteorites are	rocky and primitive.
A rocky leftover planetesimal orbiting the Sun is	an asteroid
How can we determine an asteroid's reflectivity?	by comparing its infrared thermal emission to its visible-light reflecti
In order to have a comet named after you, you have to	be one of the first three discoverers who report it to the International Astronomical Union (IAU).
Where did comets that are now in the Oort cloud originally form?	near the jovian planets
Halley's comet is named after the English scientist Edmund Halley because he	calculated its orbit and predicted that it would return in 1758.
The number of comets in the Oort cloud is probably about	a trillion.
What do we call a small piece of solar system debris found on Earth?	meteorite
Primitive meteorites can be distinguished from other meteorites and terrestrial rocks because they	contain a noticeable fraction of pure metallic flakes
An icy leftover planetesimal orbiting the Sun is	a comet.
Why was the Shoemaker-Levy 9 impact so important to astronomers?	It dredged up material that gave us our first direct look at Jupiter's interior composition.
Which of the following does not lend support to the idea that Pluto is a Kuiper-belt object?	Pluto is smaller than many known comets, such as Halley's comet.
Most meteorites collected on Earth are of the rocky primitive variety, although most asteroids are of the carbon-rich variety.	True
A spacecraft traveling through the asteroid belt has a high risk of being destroyed through a collision.	False
No spacecraft has ever visited an asteroid or comet.	False
Comet nuclei can be darker than charcoal	True
Oort-cloud comets are so far from the Sun that the gravity of neighboring stars can alter their orbits.	True
Pluto's gravity affects the orbit of Uranus, and this fact was used to discover Pluto.	False
Why aren't small asteroids spherical in shape?	The strength of gravity on small asteroids is less than the strength of the rock
Meteorites can come from	mars, moon, ancient lava flows, the cores of asteroids
Why aren't small asteroids spherical in shape?	The strength of gravity on small asteroids is less than the strength of the rock
Meteorites can come from	mars, moon, ancient lava flows, the cores of asteroids