Astronomy Exam #4
If life is based on information, what is that information?
DNA- genetic information passed along to an offspring.
What evidence is there that Neptune's moon Triton has been geologically active recently?
Dark smudges mark the location of active nitrogen geysers.
Why is almost every solid surface in our Solar System scarred by craters?
A few of the craters have been formed recently by the steady rain of meteorites that falls on all the planets in the solar system, but most of the craters appear to have been formed 4 billion years ago in what is called the heavy bombardment, as the last of the debris in the solar nebula was swept up by the planets
How can a moon produce a gap in a planetary ring system?
A moon can produce a gap in a planetary ring system by being in orbital resonance with particles in the rings
In what ways is Earth unique among the Terrestrial planets?
Contains large amounts of liquid water on its surface. Only known home for life.
Why did Venus suffer from the runaway greenhouse effect but Earth has avoided it so far?
As a result, the planet's early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.
According to the solar nebula theory, why is the Earth's orbit nearly in the plane of the Sun's equator?
Because our planetary system formed in a disk-shaped cloud around the sun
What is the difference between condensation and accretion?
Condensation is solid grains forming from gas. These grains can grow by condensation by adding one atom or molecule at a time from the surrounding gas. Accretion isthe sticking together of solid particles. The grains formed and grown byeventually can collide with other grains and combine through accretion
How does the dynamo effect account for the magnetic fields of Jupiter, Saturn, Uranus, and Neptune?
Circulation in the interior caused by ammonia dissolved in the liquid water mantle making the mantle a good electrical conductor and that convection in the water, coupled with the rotation of the planet , drives the dynamo effect and generates a magnetic field. In Jupiter and Saturn the conducting liquid is liquid hydrogen.
How does the solar nebula theory explain the dramatic density difference between the Terrestrial and Jovian planets?
Different densities form at different distances because different materials forms at different distances from the sun.
What are the four stages of planetary development?
Differentiation, cratering, flooding and surface evolution.
What are the seasons on Uranus like?
Each of the four seasons last 21 years due to Uranus rotating on its side and an orbital period of 84 years. During a season when one of the poles is pointed at the sun, the inhabitants would never see the sunrise or sunset.
What produced the iron and heavier elements like gold and silver in Earth's core and crust?
Elements heaver than iron are produced by rapid nuclear reactions occurred in explosions of some massive stars
What does the term differentiated mean when applied to a planet? Would you expect to find that planets are usually differentiated? Why?
Elements separating into different regions of density when the planet is warm enough.Yes, because stability relations are not identical and components will migrate from less stable to conditions to more stable conditions.
What evidence indicates that catastrophic impacts have occurred in the Solar System's past?
Evidence is the backwards orbit of moons and Uranus is tilted, misalignment of orbital planes.
What evidence can you cite that planets orbit other stars?
Extrasolar planets. The wobble of their rotation is detected by Doppler.
What produced the helium now present in the Sun's atmosphere? In Jupiter's atmosphere? In the Sun's core?
Helium in the sun's atmosphere is produced by sun's nuclear fusion. Helium in the sun's core and Jupiter is produced after a few minutes of the big bang.
Why does the solar nebula theory predict that planetary systems are common?
If our solar system formed from the disk of gas and dust that surrounded the sun as it condensed from the interstellar medium, then it is a common process. Most stars form with disks of gas and dust around them and planets should form in such disks
Why do astronomers think the asteroids were never part of a full-sized planet?
If the asteroids were once part of a single large body, that body would have differentiated into a core, mantle, and crust, but most asteroids appear to be undifferentiated.
Give an example of natural selection acting on new DNA patterns to select the most advantageous characteristics.
In a cold environment, squirels with thick fur coats will survive longer and reproduce more while squirels wiht thin fur will slowly die off.
How do island chains located in the centers of tectonic plates such as the Hawaiian Islands help you understand plate tectonics?
It shows that plates move because as they move over hot spots they create volcanoes
What do chondrules tell you about the history of chondrites?
It shows that the temperatures of the chondrites do not reach a high enough temperature to melt them.
What would happen to a life-form if the genetic information handed down to offspring was copied extremely inaccurately? How would that endanger the future of the life-form?
It would produce fatal mutations. Affected organisms would die before they could reproduce, thus endangering the future of the life-form.
Why don't Terrestrial planets have rings like the Jovian planets?
Jovian planets have larger mass and their distance from the sun makes them not as quickly swept away from radiation pressure and solar wind
How can Jupiter have a liquid interior and not have a definite liquid surface?
Jupiter and Saturn are so large that the gas is compressed in their interior until the hydrogen becomes a liquid. Because the bulk of both planets consists of compressed, liquefied hydrogen, we should really call them liquid planets.Under the force of gravity, the heavier elements sink toward the inner parts of a liquid or gaseous planet.
Why is Jupiter so much richer in hydrogen and helium than Earth?
Jupiter formed further out in the solar nebula than Earth, and due to the temperature gradient in the nebula, its immediate environment was quite a lot cooler than that of the Earth.As such, Jupiter formed from a conglomeration of icy planetesimals and grew rapidly from gravitational collapse, enabling the planet to imbibe gas directly from the nebula itself since it had the self-gravity to hold lighter molecules like hydrogen and helium.Large self-gravity means a large escape velocity, so it is much more difficult for molecules to reach the kinetic energy needed to escape the gravity of Jupiter than that of Earth. Jupiter therefore has a much greater concentration of hydrogen and helium than Earth does.
How do observations of meteor showers reveal one of the sources of meteoroids?
Meteor showers seem to come from a single point of the sky, meaning they are travelling along parallel paths
How is the composition of meteorites related to the formation and evolution of asteroids?
Meteorites contain a record of impacts during all stages of asteroid origin and evolution.The formation and growth of chondritic particles; the change, metamorphism and meltingof asteroids; and the erosion and disruption of asteroids by hypervelocity impacts. A review ofmeteorite classification shows that numerous meteorites are not readily classified because theydo not fit simple models for asteroid formation and evolution that assume impacts were onlyimportant during the final stage of asteroid evolution and because of inadequate understandingof a steroidal impacts. Chronological, textural, and thermal constraints allow us to identify meteorite impact breccias that formed during accretion
How can most meteors be cometary if all meteorites are asteroidal?
Meteors are pieces of the nuclei of comets that fall through our atmosphere whenever the earth�s orbit takes us through a cometary tail.� Since comet nuclei are mostly made of ice and other volatiles, they easily burn off due to friction with the earth�s atmosphere, producing the bright trails we associate with meteor showers.� Asteroids, however, are made of mostly rock, which is much more robust than ice and won�t tend to burn up as easily when the asteroid falls through our atmosphere.� Thus one doesn�t see the bright streaks when an asteroid falls to the ground,� and more of the asteroid tends to survive its fall and become a meteorite.
Why do astronomers refer to carbonaceous chondrites as unmodified or "primitive" material?
No erosion, no exposure to oxygen to rust or oxidize, only cosmic ray and photon exposure (if on the surface). Below the surface, the material has never been altered from when it was formed. So it is unmodified or primitive material from the period when the sun and planets were formed
Why do short-period comets tend to have orbits near the plane of the Solar System?
Short period comets only go out as far as the outer planets and thus have periods less than 200 years. Long period comets have orbits that reach out toward the Oort Cloud and have periods many thousands of years long.
Why would you include the Moon in a comparison of the Terrestrial planets?
Solid rock like the terrestrials, but smaller than any of them, and unlike them does not orbit the Sun. Also its density is lower than the density of any terrestrial
What evidence indicates that the asteroids are mostly fragments of larger bodies?
Some asteroids collide, releasing fragments which are then collected by other asteroids.
Why do astronomers suspect that Saturn's moon Enceladus is geologically active?
Some parts of its surface contains 1000 times fewer craters than other regions, and infrared observations show that the polar region is unusually warm and venting water and ice geysers. Evidently a reservoir of water lies only tens of meters below the surface. At some point, this moon must have been in resonance with another moon causing tidal heating.
What evidence indicates that some asteroids have had geologically active surfaces?
Spectroscopically, Vesta appears to have regions of small lava flows
How do you know that Earth differentiated?
That Earth differentiated is supported by three observations. First, the mean density of Earth is significantly greater than the mean density of its surface. The mean surface density of Earth is about 3 g/cm3, while the mean density of Earth is 5.5 g/cm3. This doesn't prove that Earth is differentiated, but it does mean that the density of the interior of Earth is much greater than the surface, as would be expected if Earth is differentiated. Second, seismic data can be used to determine the density variations of Earth's interior. These indicate that the density of Earth decreases from the center to the surface. Finally, the strength and variation of Earth's magnetic field indicate that it is formed by a process similar to the production of an electromagnet. This suggests that the core is made of a material that is a good conductor, such as an iron-nickel alloy. This again supports differentiation.
What are the hypotheses for how the bodies in the Kuiper Belt and the Oort cloud formed?
The Kuiper Belt is formed from the outer remnants of the solar Nebula, as were the bodies in the Oort cloud. As a result, much of their materials are the same (basically they are comprised of icy planetesimals of varying sizes).
Why are the atmospheres of Venus and Mars mostly carbon dioxide? Why is the atmosphere of Venus very dense but the atmosphere of Mars is very thin?
The atmosphere of Venus and Mars has a carbon dioxide mostly. The reason is that neither of these planets has liquid water on their surfaces to remove the CO2 from the atmosphere.
What evidence indicates that there has been liquid water on Mars?
The evidence that liquid water once flowed on Mars are valley networks made of valley networks (meandering riverbeds), gulleys, splash craters, outflow channels.
What do Widmanstätten patterns indicate about the history of iron meteorites?
The patterns indicate that the molten metal cooled very slowly over millions of years, and material in the iron meteorite is found in the cooling interiors of planetesimal sized objects.
Why would astronomically short lifetime of gas and dust disks around protostars pose a problem in understanding how the Jovian planets formed? What modification of the solar nebula theory might solve this problem?
The jovian planets would not have enough time to form. Rotating gas and dust of solar nebula could've become unstable and formed Jovian planets by skipping straight to step of gravitational collapse--accretion is followed by gravitational collapse.
Why do astronomers conclude that none of the Jovian planets' rings can be left over from the formation of the planets?
The rings are replenished now and then from impacts. Since the rings are icy, it is too fragile and will eventually deteriorate from radiation and impact.
How does the solar nebula theory help you understand the location of asteroids?
The solar nebula theory tells us where the densest planets will be and where the lower density planets will be in the solar system. There will be a region where planets cannot form properly and where gas giants will not form. Also it takes into account the gravitational disturbances from other planets that might rip apart any planet that may form. Thus we get the asteroid belt. We also see the Kuiper Belt beyond the solar system where asteroids are.There are also Lagrange points where asteroids are stable in planetary orbits.
What evidence indicates that plate tectonics does not occur on Venus? On Mars?
The volcanoes on Venus and Mars are shield volcanoes, which occur only when there isn't any plate activity. The lava flows through the crust and spreads out onto the surface.
What is the difference between the dense hot disks seen around some stars and the low-density cold disks seen around some other stars?
Their densities, temperatures, and locations are different.
What evidence suggests that Venus has been resurfaced within the last half billion years?
There are a relatively small number of craters on the surface, and the craters appear to be randomly distributed. This implies that the entire surface has the same relatively young apparent age.
Why are Uranus and Neptune respectively green-blue and blue?
Traces of methane absorb red light and thus make the atmosphere look blue or teal. Neptune has more methane causing it to be a deeper blue color.
Why are the belts and zones on Saturn less distinct than those on Jupiter?
They are deeper inside Saturn's atmosphere.
What makes Saturn's F ring and the rings of Uranus and Neptune so narrow?
They are narrow because shepherd moons keep the particles forming the ring in a narrow band.
How do astronomers account for the origin of Pluto?
They were created in the outer solar nebula and then got swept in by resonance when Neptune and Uranus were migrating
Why is the atmospheric activity of Uranus less than that of Saturn and Neptune?
Uranus lacks an internal energy source such as Jupiter and Saturn, and thus its atmosphere energy system is much less active, resulting in fewer features (storms, eddies, etc.).
Why doesn't Venus have as many craters as Earth's Moon or Venus?
Venus's thick atmosphere prevents all but the larger meteoroids from striking the surface. Also, Venus's volcanism has paved over the craters that were there.
What processes cleared the nebula away and ended planet building?
Very likely the solar wind during the T-Tauri stage of the star clear the last of of the gas away, or combined with ultraviolet radiation from other stars.
What evidence can you cite that disks of gas and dust are common around young stars?
We have ample evidence that shows that gas and dust clouds are common around young stars. We get that evidence by observing the nebulae where new stars form, and we can see the clouds using different areas of the spectrum
What is the water hole, and why is it a good "place" to search for extraterrestrial civilizations?
a water hole is the interval of the adio spectrum between the 21 cm hydrogen radiation and the 18 cm OH radiation, likely wavelength to use in search for extraterrestial life because any civilization sophisticated enough to do radio astronomy would know these lines and might appreciated their significance in he same way as do some earthlings.
Why are there no chondrules in achondritic meteorites?
achondrites melted after they formed, and achondritic means without chondrules
What evidence indicates that some asteroids have differentiated?
asteroids come from meteoroids and they have different properties
Why would a decrease in the density of the ozone layer cause public health problems?
because it would cause higher amounts of uv radiation to reach the surface
Why doesn't Earth have as many craters as the Moon?
because most meteorites dissolve in Earth's atmosphere and never reach the surface
What is the difference between chemical evolution and biological evolution?
biological - process of changes that occur in living beings that can be passed off to their offspring . (Life forms & natural selection)chemical - process of changes that occur in substances (most stable compound combine and stay together ) Example: WATER (H2O)
What would happen to a life-form if the information handed down to offspring was always the same? How would that endanger the future of the life-form?
everything would be same - no varietywouldn't be able to adapt
Why is it reasonable to suspect that travel between stars is nearly impossible?
fastest commercial jet would take 4 million years (distance)speed of light is the speed limit (speed)a lot of gas, need just as much gas to stop (fuel)ONE-WAY TRIP
What kind of erosion is now active on Earth's Moon?
from tiny micrometeorites that bombard it creating a layer of dust
How does the stability of technological civilizations affect the probability that Earth can communicate with them?
if a society survives at a technological leve; for only 100 yrs, the chances of communicating eith it are small. a society that stabilizes and remains technologically capable for a long time is much more likely to be detected.
What characteristics must Earth's core have in order to generate a magnetic field?
iron and other molten metals. The spin of the Earth causes the core to spin also, causing electrical charges to go through the Earth, creating a magnetic field.
why do astronomers conclude that the crust on mars must be thicker than earth's crust?
it has a large amount of volcanoes and a crust with no plates so as the planet cooled the crust grew thick and immobile
Why do scientists generally think that liquid water is necessary for the origin of life?
it is a requirement of carbon based life, necessary both as the medium for vital chemical reactions and to transport nutrients and waste
How does the increasing abundance of in Earth's atmosphere cause a rise in Earth's temperature?
it makes the atmosphere less transparent to infrared radiation so it traps the radiated heat from Earth's surface and keeps it from escaping off into space
What is the significance of the Miller-Urey experiment?
it shows that the chemical building blocks of life form naturally under a wide range of circumsances.
Why is it difficult to anticode a message?
it takes a long time for the message to travel to the intended destination and an additionally ecxtended amount of time to recieve a response.
How might intelligence make a creature more likely to survive?
more likely to escape from predators, catch prey, feed and shelter itself and its offspring. under certain conditions, evolution is more likely to select intelligence.
If you visited another planetary system, would you be surprised to find planets older than Earth? Why or why not?
no, because not all solar systems formed at the same time.
What has produced the oxygen in Earth's atmosphere?
plant life
How does the DNA molecule produce a copy of itself?
steps of semiconservative model of replication:1. parental molecule of DNA (set of base pairs)2. The parental strand separate and serve as templates3. Free nucleotides base pair along each "open" strand4. two identical daughter molecules of DNA are formed(see pg 188 fig. 10.4A)
What evidence do scientists have that life on Earth began in the sea?
stromatolites are the oldest easily identified fossils;
What evidence indicates that the climate of Mars has cyclical changes?
the different orientations of the layers of terrain
What is the difference between a gas tail and a dust tail? What does that tell you about the composition and origin of comets?
the gas tail is ionized by UV radiation from the sunlight, and is emission spectrum. the dust tail is made of dust that was contained in the vaporizing ices of the nucleus and is an absorption spectrum. it tells us how the comet was made
Explain why the amount of geological activity on Jupiter's moons varies with distance from the planet.
the geological activity decreases with increasing distance from Jupiter. The geologic activity on any world is the result of heat escaping from that body.
What is the evidence that the Solar System formed about 4.6 billion years ago?
the oldest rocks from earth, the moon, and mars have ages over 4 billion years old, found by radioactive dating. the oldest objects in our solar system are some meteorites that have ages of 4.6 billion years. If you visited another planetary
Why is the existence of "hot Jupiters" puzzling? What is the current hypothesis for how they formed?
they are large but formed near the sun--normally forming near the sun would prevent them from getting too large. they're formed in a dense disk of matter that spiraled inward as they sweep up gas and planetesimals
Why are upper-main-sequence (high-luminosity) stars considered unlikely sites for intelligent civilizations?
they burn up too fast and last too short a time for complex life to develop