3-6 Asteroids

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3-6 Asteroids
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Jupiter
Asteroid belt
Earth
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Asteroids rocky or metallic. They contain little
volatile (i.e. easily evaporated) material
Gaspara
Ida and its satellite Dactyl
Belt asteroids by Galileo spacecraft
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They differ from planets by their size
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January 1801 Giovanni Piazzi thinks he has found
a new planet between Mars and Jupiter Ceres
Artist view
HST
By 1890, more than 300 such planets had been
discovered
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1890 Introduction of photography to the search
for asteroids
Asteroid trail asteroids move relative to the
stars
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Today more than 20,000 asteroids have
well-determined orbits
We estimate that there are more than a million
asteroids with diameters larger than 1 km
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The mass of all the asteroids is less than the
mass of the Moon
Asteroid belt the typical spacing between two
asteroids larger than1 km is several million
kilometers
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Majority as dark as a lump of coal, made of rock
Primitive bodies dating from solar system
formation
Some reflect 60 of the incoming sunlight,
composed of metal
Come from a large body with molten interior that
was shattered by a collision
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Trojan asteroids
If you put an asteroid on the Earth orbit, would
it Stay on the orbit? Drift away? Crash into
our planet?
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It depends on where you place the asteroid.
There are five points, known as the Lagrange
points, where an asteroid will remain stationary
with respect to the Earth
Asteroids placed anywhere else will drift around
in various ways
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The most stable positions are L4 and L5
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Jupiters L4 and L5 asteroids are named after
Trojan heroes, so we call them Trojan asteroids
The name Trojan is now used for any other planet
Earth Trojans
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Launched 1996
Near Earth Asteroid Rendezvous NEAR
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Eros
Impact craters
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Eros
Loose material
Dotted with half buried boulders
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NEAR last images (Feb 2001)
250 m
120 m
Lost signal
amazing profusion of boulders
collapse feature, formed when support is removed
from below the surface
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• Terrestrial planets
• self-assessment quiz

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1. Which of the following properties do the terrestrial planets, Mercury, Venus, Earth, and Mars, have in common?
F) They all orbit the Sun in a year or less.
D) They all have solid surfaces.
C) They are all cloud covered.
G) They all have very dense atmospheres.
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2. Mercury can be seen easily from Earth only
A) during a lunar eclipse, when the sky is sufficiently dark near to the Moon, because Mercury is always close to the Moon in our sky.
O) at midnight, when it is high in the sky.
E) near to the Sun, just after sunset or just before sunrise.
U) in the winter, when the ecliptic plane is high in the sky at night.
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3. Which of the planets fits the following description A planet with solid, cratered surface, which is alternately very hot and very cold, and having no atmosphere?
E) Venus
A) Mercury
I) Jupiter
O) Mars
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4. Which planet most resembles the Moon in visible surface features and atmosphere?
R) Mars
P) Venus
C) Uranus
T) Mercury
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5. Mercury is always much closer to the Sun than is Venus and yet it never appears brighter than Venus even when at maximum brightness. Why is this?
M) We never see more than a small fraction of Mercury's illuminated surface because of its orbital path relative to that of the Earth hence it always appears dark.
B) Because Mercury has a thick atmosphere that impedes reflection from its surface, making it appear dark.
K) Because Mercury has a high reflectivity but is very small, and hence appears relatively dark.
H) Because Mercury is small, has a dark surface, and has no reflecting clouds.
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6. Which of the following statements about the similarities of Mercury and our Moon is NOT true?
A) They both have heavily cratered surfaces.
B) They both have very dark surfaces or low reflectivities.
C) They both have large, circular, and relatively flat basins or maria on parts of their surfaces.
D) They have no atmospheres.
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7. What evidence does a planetary geologist use to identify a young crater on Mercury?
A) Observation of few, if any, smaller overlapping craters within it or on its rim.
B) Infrared and photographic results showing evidence of water released recently from the permafrost by the impact.
C) Observation of a lighter-colored central region, because an older crater would have acquired a layer of dark dust over time.
D) Observation of a sharper rim and central peak compared to older craters. Old craters would have suffered significant erosion by wind and dust.
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8. How has the age of Mercury's intercrater plains been estimated?
S) From residual radioactivity within the plains compared to areas outside, as measured by the Mariner 10 spacecraft.
T) By comparing the reflectivity of the plains to areas outside, because material becomes lighter as it gets older, as it does on the Moon.
R) From radioactive dating of rocks returned to Earth by the Mariner 10 spacecraft.
P) By comparing the number of craters per unit area within the plains to areas outside.
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DEATH CAP
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9. Craters on Mercury appear to have been produced by
S) impacts from objects from space, early in the planet's history.
R) successive expansion and contraction of the planet's surface because of intense heating by the Sun and severe cooling during rotation, because the craters appear to be in irregular lines across the surface.
C) volcanic eruptions, early in the planet's history.
D) impacts by objects from space, continuously throughout the planet's history, including very recently in geological time.
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10. What caused the long, meandering scarps (cliffs) that can be seen on Mercury?
A) Volcanic eruptions along crustal faults over hot-spots in the mantle.
E) Crustal movement similar to continental drift on Earth, where plates have pressed against one another.
I) Shrinking and folding of the planet's surface as it cooled.
O) Large impacts near the end of the early period of heavy bombardment, the scarps being eroded crater walls.
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11. Mercury's atmosphere is
M) almost non-existent.
N) relatively dense, composed mostly of nitrogen (80) and oxygen (20).
P) very thin, made up of sulfur dioxide and hydrogen sulfide from volcanoes.
R) relatively thin, composed of carbon dioxide with small quantities of nitrogen and argon.
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12. Because Mercury has no appreciable atmosphere, its surface shows extreme temperature changes between night and day, with a range of about
P) 600 degrees
Q) 1200 degrees
R) 150 degrees
S) 60 degrees
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13. Temperatures on the surface of Mercury are seen to fluctuate between a very cold 100 K (173C) and an extremely hot 700 K (427C). What does this measurement indicate about conditions on Mercury?
R) Mercury has a very elliptical orbit, and varying distance from the Sun produces these large temperature fluctuations, because intensity varies as the inverse square of the distance from the Sun.
T) The planet has an atmosphere in which the greenhouse effect captures solar radiation to heat the sunlit hemisphere of the planet.
S) The planet is close to the Sun, has no atmosphere to maintain heat from the Sun, and is rotating.
P) Erupting volcanoes occasionally heat the planet's surface to extreme temperatures.
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14. Compared with that of the Earth, Mercury's magnetic field is
O) weak but clearly present.
E) below the limit of detection and therefore still needs confirmation.
I) similar in strength.
U) much more powerful.
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15. Two conditions appear to be necessary for the generation of a powerful magnetic field in planets that are NOT present simultaneously on Mercury. These conditions are
N) rapid rotation and a molten iron core.
M) a molten core and a significant atmosphere.
L) rapid rotation and a conducting atmosphere.
J) a solid surface and a significant iron content.
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16. On the basis of its appearance and general properties, which planetary body could be described as the Earth's twin?
T) Mars somewhat smaller but with a similar surface, a thin atmosphere, and clouds.
P) The Moon somewhat smaller but having the same average density and geology.
R) Pluto it has a similar size and density, a large moon, and probably life on its surface.
S) Venus with about the same mass and diameter, dense atmosphere, and cloud shrouded.
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SIMPSONS
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17. Which of the following physical properties of Venus are very similar in value to those of Earth?
C) Mass and radius and hence average density and surface gravity.
B) Rotation rate around its axis and length of solar day.
D) Temperatures of surface and atmosphere.
A) Magnetic field and magnetosphere.
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18. Compared to the length of a solar day upon Earth (i.e., time between successive sunrises), the length of one solar day on Venus is
O) about the same.
I) much shorter, about 1 hour.
E) about half as long, about 10 hours.
A) significantly longer.
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19. An Earth-based telescopic view of Venus shows
P) a crater-covered surface of reddish color.
L) evidence of ice-covered polar caps and huge dust storms.
N) a smooth, dark surface with few mountain ranges.
M) a completely cloud-shrouded planet with high atmospheric wind speeds.
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20. Which is the hottest planet in the solar system, measured at the surface?
A) Earth.
I) Mars.
E) Venus.
O) Mercury.
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21. The surface pressure of the atmosphere of Venus compared to that of Earth is
P) about the same as Earth.
L) extremely small.
N) about 1/100 atmosphere.
M) about 90 atmospheres.
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22. The conditions on the surface of Venus are
A) no atmosphere, and hence very variable temperatures under direct sunlight.
D) a low pressure, low temperature, CO2 atmosphere.
B) a high pressure, high temperature, CO2 atmosphere.
C) a dense atmosphere of methane, ammonia, and H2O, at a low temperature.
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23. Tomorrow's weather report for Venus would be
E) overcast and very hot.
O) cold and clear.
U) snow.
I) hot and humid, with clear skies.
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24. The clouds in the atmosphere of Venus consist primarily of
P) dust particles.
S) droplets of CO2.
T) H2O.
R) droplets of H2SO4 or sulfuric acid.
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25. There are many reasons why a multi-day hiking trip on foot across Aphrodite Terra on Venus would not be advisable, at least not without suitable protection. Which of the following would NOT be a concern?
V) Corrosive mists in the atmosphere.
T) Very cold nighttime temperatures.
S) Predominantly carbon dioxide atmosphere.
R) Water not available.
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CAMEMBERT
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26. The mechanism of the greenhouse effect can be described as
T) solar UV and visible radiation heating the planet surface, the infrared emissions of which are trapped by CO2 in the atmosphere.
R) solar UV and visible radiation entering the clouds and triggering chemical reactions in the CO2 and sulfur compounds, the released energy then heating the atmosphere.
S) solar UV and visible radiation being absorbed by the CO2 of the atmosphere, thereby heating it.
P) solar infrared radiation heating the planet surface that then emits visible and UV radiation which is trapped by CO2 in the atmosphere.
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27. The component of Venus's atmosphere that is responsible for the excess heating, caused by the greenhouse effect, is
A) H2O vapor.
E) N2.
I) CO2.
O) H2SO4 or sulfuric acid droplets.
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28. Why has the greenhouse effect been much more effective in raising the surface temperature on Venus than upon the Earth?
S) Because Venus has no magnetic field to deflect this solar wind. atmosphere.
R) Because CO2 is the major component in the Venusian atmosphere while it is a only a minor constituent of the Earth's.
P) Because the oceans upon Earth have acted as a thermostat in absorbing much of the heat that would otherwise have raised the Earth's temperature significantly.
T) Because the surface of Venus is much more effective than that of Earth in absorbing solar visible and UV radiation.
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29. The surface features and overall topology of Venus have been determined primarily by
U) balloon-borne spacecraft, launched into the Venus atmosphere by spacecraft.
O) surface lander vehicles that have explored the surface thoroughly.
E) visible and UV photography from the Space Shuttle.
A) radar methods from Venus-orbiting spacecraft, measuring radio echoes from the surface.
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30. The most common surface features on Venus are
L) impact craters.
N) ancient river valleys and huge flood plains.
P) evidence of plate tectonic motion, including long mountain ranges and subduction troughs.
M) volcanoes and lava flows.
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31. The reason why very few impact craters are seen on Venus compared to the Moon is believed to be that
A) Venus formed closer to the Sun than did the Moon, where the cratering rate was much lower.
O) erosion due to rainfall and wind has eroded away all but the most recent craters.
I) lava flows and surface melting have covered all but the most recent craters.
E) the surface of Venus has been subducted back down into the planet several times in its history, thereby removing evidence of impacts.
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32. Where would the Sun appear to rise on Venus, if you could see through the clouds?
R) In the north, because Venus has its spin axis parallel to the plane of its orbit.
S) In the west.
T) In the east.
U) The Sun would not rise or set because Venus rotates synchronously, always keeping one side toward the Sun.
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33. At opposition, when Mars comes relatively close to Earth, where would it be seen in the sky by an observer in the Earth's northern hemisphere?
A) High in the south at sunset.
O) On the western horizon at midnight.
U) High in the south at midnight.
E) High in the north at midnight.
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TIRAMISU
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34. On which planet can we see prominent but variable ice caps?
A) Mercury
B) Mars
C) Venus
D) The Moon
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35. In which of the following physical characteristics are Earth and Mars most similar to each other?
E) Total mass.
O) Number of moons.
A) Length of solar day.
I) Planetary diameter.
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36. In what way did optical illusion mislead earlier visual observers of Mars?
L) Chance alignments of faint dark features looked like manufactured canals, and variable dark areas near the equator were interpreted as vegetation.
M) Moving areas of obscured detail on the planet were interpreted as massive flash floods rather than dust storms.
N) Apparent movement of surface features were interpreted as evidence of movement of life-forms or Martians.
P) Volcano structures were seen as eye-shaped images, and were interpreted as having been made by intelligent beings to indicate their presence on Mars.
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37. The so-called canals that Schiaparelli and Lowell reported seeing upon the surface of Mars were actually
E) the remnants of the walls of ancient craters that have been eroded by winds and dust over Mars's history.
O) river valleys, caused by massive floods early in Mars's history.
U) lines of volcanoes along faults in the Martian surface.
A) optical illusions.
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38. What is the face on Mars?
L) A natural rock formation that looks like a face in the right lighting.
M) A small carved portrait placed on the Martian surface by one of the Viking landers.
N) A sculpted hill carved either by a long-dead Martian civilization or by visiting aliens.
P) A natural arrangement of volcanoes and lava plains that gives the appearance of a face when viewed from Earth.
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39. A major feature of the atmosphere of Mars is
I) very dense clouds shrouding most of the planet.
E) very high temperatures and pressures.
A) occasional strong winds and dust storms.
O) a chemical mixture very similar to that of Earth.
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40. The overall geography of Mars can be best summarized as
A) moving lithospheric plates whose motions have produced long folded mountain chains, deep subduction trenches, and several large rift valleys.
E) mostly rolling plains, with several volcanoes on top of two continent-sized uplands.
O) smooth plains where continuous resurfacing by ongoing volcanic activity has hidden older impact craters and other details.
I) major volcanoes in the northern hemisphere, extensively cratered plains in the southern hemisphere, separated by one major valley system.
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41. Olympus Mons is
L) a long-lived anticyclone or spot on Jupiter.
N) a valley on the Moon.
M) a mountain on Venus.
K) a volcano on Mars.
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42. A caldera is
A) a crater formed by collapse at the summit of a volcano.
B) a valley formed by the separation of two crustal plates.
C) a long, sinuous valley carved by the flow of molten rock.
D) a depression formed by the impact of an asteroid on a planetary surface.
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BALALAIKA
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43. There are many reasons why a multi-day hiking trip on foot through the Valles Marineris on Mars would not be advisable, at least not without suitable protection. Which of the following conditions would NOT be a concern?
F) The possibility of dust storms.
D) The predominantly carbon dioxide atmosphere.
C) High levels of ultraviolet radiation.
B) Oppressively high atmospheric pressure.
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44. How have we obtained samples of Martian rocks?
O) Rocks collected and returned to Earth by astronauts.
E) We have not yet been able to obtain any Martian rocks.
A) Rocks blasted off Mars by impacts, and landed on Earth as meteorites.
U) Sample return missions, where a robotic rover collected rocks for return by the lander.
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45. In view of the present surface and atmospheric conditions on Mars, why would there be no liquid water on its surface?
M) The water would all be frozen, given the prevailing day and night temperatures.
N) The very low atmospheric pressure would allow the water to boil and evaporate rapidly.
L) It would have reacted chemically with the surface rocks.
P) The UV radiation from the Sun would have dissociated the molecules into hydrogen (which would leave the planet) and oxygen, which is still present.
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46. The polar caps on Mars are most likely made up of
A) volcanic outflows of light-colored lava and dust similar to that produced by Earth-based volcanoes (such as Mt. St. Helens).
B) sulfur dioxide and sulfur compounds.
C) light-colored dust, blown there by the Martian dust storms.
D) water and CO2 ices.
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47. On which planetary body can distinct evidence be seen for the flow of water at an earlier time?
O) Mars.
I) The Earth's Moon.
A) Venus.
E) Titan, the moon of Saturn.
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48. What significant evidence is there for the idea that large quantities of water once flowed on the planet Mars?
P) A network of relatively straight canals linking polar and equatorial regions.
R) Clouds and frost that formed above and around the Viking spacecraft.
S) Frozen, dust-covered lakes inside ancient craters.
N) Deep, winding canyons and flood plains.
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49. We know that water exists on Mars, but where and in what state does it NOT exist on this planet?
E) Flowing in river valleys.
I) In polar icecaps.
O) As water vapor in the atmosphere and as clouds.
U) In permafrost, below the surface.
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50. The equator of Mars is tilted with respect to its orbital plane, and so Mars
O) shows similar seasons to Earth, each season lasting about twice the length of seasons on Earth.
E) experiences very long (20 year) seasonal variations.
A) occasionally experiences small seasonal variations.
I) shows no seasonal variation at all.
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52. The reddish color of Mars is probably due to
M) the glow from the very high temperature surface on the sunlit parts of Mars.
N) iron oxides such as rust.
P) vegetation turning red in the Martian autumn.
R) sulfur compounds thrown out by active volcanoes.
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BANDONEON