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From your textbook's chapter 8.1, how do we know that the Earth’s core is largely made up of very dense iron as opposed to the lower density types of rock that make up its crust?
Earth has heavier metals at its center making a dense core. The innermost part of the core is solid, and earth has different layers of density.
From your textbook's chapter 8.2, we learned that Alfred Wegener studied the Earth’s surface extensively and came up with a theory to explain the major surface features. (a) Explain what his theory proposed, then (b) provide two examples of evidence that supported his hypothesis about the Earth.
a) landmasses of different continents were once together (Pangaea)
b) 1. similar fossils found in South America and Africa2. resemblances among living animal species on different continents
From your textbook's chapter 8.2, regarding Wegener's theory: (a) what was the major argument against his hypothesis, initially? (b) describe how this was eventually addressed by describing what causes continents to drift.
a) missing mechanism
b) plate techtonics: continental plates float on mantle and drift
From your textbook's chapter 8.3, we know that the temperature of the atmosphere cools as you get further and further above the surface. But about 50 km above the surface of the Earth (in the stratosphere), the temperature starts to warm up. Explain what causes this warming in the stratosphere.
The breakup of ozone adds heat to the stratosphere because ozone absorbs uv light and protects the surface from the sun’s uv radiation.
From your textbook's chapter 8.3, briefly describe what we think are the two main sources of the Earth's original atmosphere (three possible sources are mentioned but only the latter two are significant).
1- atmosphere released from interior through volcanic activity
2- atmosphere may have been derived from impacts by comets and asteroids from outer parts of the solar system
From your textbook's chapter 8.4, describe two changes the occurred in the Earth's atmosphere about 2 billion years ago that allowed Oxygen to become more abundant in our atmosphere.
1- increase evolution of life led to a growth in plant population and increased Oxygen production
2- increased geological activity led to erosion burying plant carbon before it could recombine with oxygen
From your textbook's chapter 8.4, explain why the presence of Oxygen allowed for life to move out of the oceans and grow increasingly diverse.
Oxygen accumulated in the atmosphere increased oxygen gas that lead to the ozone layer which protects the surface from deadly solar UV radiation.
From your textbook's chapter 9.1, describe two major differences between the composition of the Earth and the Moon.
1- moon made almost entirely of silicate rock
2- moon is depleted in iron and other metals
From your textbook's chapter 9.1, although the Moon has no atmosphere, water-ice does exist on the surface in some places. Explain how this is possible.
The water was presumably carried to the moon by comets and asteroids that hit its surface. Water froze in cold regions where sun never shines deep in its craters.
From your textbook's chapter 9.2, why are the mountains of the Moon mostly smooth and rounded in shape instead of sharp and steep like many of the mountains on Earth?
There is no atmosphere or water on the moon, there is no wind, water, or ice to carve its mountains into cliffs and sharp peaks like on earth.
From your textbook's chapter 9.3, explain (a) why scientists first proposed (two reasons) that craters on the Moon were due to impacts rather than volcanism and (b) why almost all of the lunar impact craters are circular instead of oval.
a) moon craters are larger and have different shapes from known volcanic craters on earth; volcanic craters are smaller, deeper, and usually at the top of volcanic mountains
b) due to escape velocity, the minimum speed that a body must reach to permanently break away from gravity
From your textbook's chapter 9.3, describe the evidence in the lunar maria and highlands that indicates the cratering rate on the Moon hasn’t always been constant, but instead there was an early era of heavy bombardment, then a slower, constant rate from that point forward.
The cratering rate = the number of craters on the lunar maria or calculated from the number of potential asteroids and comets present in the solar system. There are ten times more craters on the highlands than on a similar area of maria.
From your textbook's chapter 9.5, describe how radar measurements of Mercury revealed its rotation rate to astronomers on Earth (explain or use a simple diagram to show what the observations would look like if Mercury were rotating slowly vs quickly and explain the difference).
Send pulse 2 planet with particular wavelength because mercury is spinning, some pulse is redshifted and some is blueshifted.
From your textbook's chapter 9.5, what is the origin of the long cliffs or scarps on the surface of Mercury?
These long, curved cliffs appear to have their origin in the slight compression of mercury’s crust. At some point, the planet shrank, wrinkling the crust, after most of the craters on its surface had already formed.
From your textbook's chapter 10.2, describe two ways that the thick atmosphere of Venus affected the appearance (or lack of appearance) of craters on the surface of Venus.
1- craters are broken in the atmosphere before they hit the surface of Venus
2- thick atmosphere absorbs the bluer colors of light so everything is orange
From your textbook's chapter 10.3, describe how the runaway greenhouse effect may have changed the atmosphere of Venus from its original Earth-like state to the mostly CO2, extremely hot world we see today.
additional heating can lead to an increase in water evaporation and release of gas from surface rocks. The increase in CO2 and H2O gas amplifies the greenhouse effect and leads to more heat, creating a cycle of increase heat and CO2 and H2O gases.
From your textbook's chapter 10.4, a small sample of meteorites found on Earth’s surface over many years is composed mostly of volcanic basalts. Explain the two arguments Astronomers have used to deduce that the meteorites likely originated from the surface of Mars.
Analysis of tiny gas bubbles trapped inside meteorites match the atmospheric properties of mars.
From your textbook's chapter 10.4, why do we think the largest Martian volcano, Olympus Mons, may still be active?
Has very few impact craters, surface is young, fresh-looking lava leads geologists to the conclusion that it might remain active.
From your textbook's chapter 10.5, runoff channels (that look like dried up river deltas) are by-products of a time when Mars had continuously flowing water on its surface. About how old are these channels, and how do we know their age?
Probably older than lunar maria, 4 billion years old, by looking at their cratering record that shows that part of the planet is more cratered than lunar maria but less cratered than the lunar highlands. CREATER DENSITY
From your textbook's chapter 10.5, one of our Martian rovers (Opportunity) appears to have landed in an old lakebed that contained a salty lake at one time. What are two arguments Astronomers use to argue that the landing site was once underwater?
1- layered sedimentary rock containing chemical evidence of evaporation
2- rocks had small spheres that were rich in mineral hematite, which only forms in watery environments
From your textbook's chapter 10.5, describe the positive feedback cycle (the "runaway refrigerator" effect) that the authors speculate may have led to the loss of the Martian atmosphere.
Runaway refrigerator effect = opposite of runaway greenhouse effect
Mars had high surface temperatures but because it’s a smaller planet and has low gravity, atmospheric gases could escape easily, thus the surface temperature fell. Mars became to cold that most of the water froze out of the atmosphere, reducing mars ability to retain heat.
From the Scientific American article "Mars in Motion," the "gullies" observed frequently on Mars were originally thought to be some manifestation of flowing water (though there were problems with this hypothesis as mentioned at the opening of the article). Eventually, the HiRISE mission came up with enough observational data to convince scientists that the gullies are caused by sublimation of carbon dioxide frost. Explain two lines of evidence that led scientists to this conclusion.
1- the pattern of gullies formed predominantly on pole-facing slopes matched the seasonal distribution of carbon dioxide frost
2- the gullies were more active in the southern hemisphere than in the north because the southern winters are longer than northern winters, so more frost accumulates.
From the Scientific American article "Mars in Motion," another type of feature observed on Mars is the "Recurring Slope Lineae" (or RSL). Describe two arguments to suggest these are associated with flowing water (one from page 62, one from page 65).
1- Surface of mars is very salty --> water on the surface must contain high levels of salt -> when it cools, it freezes and salt precipitates so leftover liquid left over is water with enough salt concentration to remain liquid
2- peak RSL activity corresponds to peak temperatures in the shallow subsurface. If summer temps are warm enough to melt the briny ice, then ice should disappear over time but cant tell since RSL are only active for a few years or decates, or the water is somehow replenished.
From the Scientific American article "Mars in Motion," explain why the Southern Hemisphere on Mars has more extreme seasons (warmer summers, colder winters) compared to the northern hemisphere.
Mars follows an elliptical orbit that carries it significantly closer to the sun. With its orbital orientation shifts, mars reaches its closest point in its orbit around southern summer, producing relatively hot summers on that hemisphere.
From the Scientific American article "How to Search for Life on Mars," (a) describe how the first Viking experiment searched for life in the Martian soil, and (b) explain how the presence of perchlorate in the soil explains the "false positive" results from Viking.
a- Dug up soil and added (carbon compounds) food for microorganisms -> observe co2 release if microorganisms exist in soil
b- perchlorate also releases CO2 so it made it seem as though the soil was releasing CO2 due to the food, but it was really perchlorate
From the Scientific American article "How to Search for Life on Mars," one modern approach suggested by the article for detecting life on Mars involves searching for DNA molecules. What's the argument against this approach?
DNA may not occur in alien life or it may be different to ours that our DNA detectors will miss it.
From the Scientific American article "How to Search for Life on Mars," another approach for detecting life would be to look for certain proteins in the soil. Describe two strategies suggested to select which proteins to look for out of the millions of possibilities.
1- search for proteins that would be useful or essential to survival on mars
2- target molecules that are ubiquitous throughout microbial world and are used by all living organisms on earth to transport chemical energy for metabolic activity.
From the Scientific American article "How to Search for Life on Mars," describe two important factors that make it more probable for life to be present, which will then help us to select a landing site for this proposed mission to Mars.
If we find biological molecules on mars that indicate life arose independently from life on earth, such as ice and salt, that continue to support liquid water was once on mars, we can choose a landing site.
From the video "The Clean Room," how can we figure out how much lead was originally present in any given rock on the Earth, given that these rocks have changed their compositions over time while on the Earth.
Use Meteorites to measure the amount of lead in them to see how much was originally present.
From the video "The Clean Room," when Clair Patterson tried to measure the amount of lead in zircon crystals, he got wildly inconsistent results, unlike his colleague's measurements of uranium in the same crystals. Explain what was causing the problem with Patterson's experiment.
They were inconsistent because of lead contamination so he had to isolate the sample by ionizing it.
From the video "The Clean Room," (a) although lead is toxic and may have eventually led to the downfall of the Roman Empire, why was it used so much by the Romans? (b) Also, explain two ways in which lead harms humans at a microscopic level.
a) The use lead because it was cheap, malleable, easy to work with, and people who were exposed to it were expendable because they were slaves.
b) 1- lead mimics other irons in our body that we need to grow
2- lead blocks neurotransmitters (communicators between cells) and messes with receptors vital for memory and learning.
From the video "The Clean Room," explain how Dr. Patterson discovered that lead is not naturally abundant in the environment but instead had increased dramatically in our environment within the past hundred years or so.
He measured the concentrations of lead from deep and shallow sea water. The deep water had low concentrations of lead, but the shallow water had high concentrations of lead. This means that the surface water’s lead had arrived recently. He discovered that it was due to leaded gasoline.
From the short video "Birth of the Moon," explain how the lunar maria formed and why their appearance is so dark compared to the lunar highlands.
Collisions formed large basins that filled in to become the dark colored patches of the moon known as maria. They began as normal craters, but soon started to change due to the size of impact on the relatively thin crust. Lava sleeked out through the cracks of impacts and filling them in and cooling. Because of high iron, the maria reflects less light and therefore is seen darker.
From the video "Crash Course: Tides," the strength of the tidal force depends on three things. Briefly describe each of these three things.
1- how strong the gravity is from the first object. The stronger the force of gravity, the stronger the tidal force will be on the affected object
2- how wide the affected object is. The wider it is, the more force of gravity from the first object changes across it and the bigger the tidal force
3- how far the affected object is from the first object. The farther away, the lower the tidal force will be.
From the video "Crash Course: Tides," explain why the Earth has TWO tidal bulges and not just one that is closer to the Moon.
The side of the earth facing the moon feels a stronger pull towards the moon than the earth’s center, so it is pulled away from the center. The side facing away from the moon feels a weaker force towards the moon than the earth’s center so the center is being pulled away from the far side.
From the video "Crash Course: Tides," what causes the Moon to move gradually further away from the Earth over a very long time?
The buldge nearest to the moon has some mass and gravity that pulls on the moon forward in its orbit. The moon responds to this tug by going into a higher orbit so the moon is actually moving away from the earth.
From the video "Crash Course: Tides," what causes “extra high” high tides, even higher than what you would normally see during Spring tides? These kinds of tides are called proxigean tides.
The moon orbits the earth on an ellipse so when it’s closest to us, we feel a stronger effect. If this happens at New or Full moon, there is an added kick to the spring tides, which we call proxigean tides and can lead to flooding in low-lying areas.
From the video "Venus Could Have Supported Life for Billions of Years: "explain how we know that Venus once likely had shallow seas all over its surface with depths ranging from a few feet to perhaps hundreds of feet.
Venus had double the amount of nitrogen earth does in its atmosphere and an abundance of carbon dioxide that planetary scientists were able to calculate that it had shallow seas but lost water within the first hundred million years.
From the video "Venus Could Have Supported Life for Billions of Years: "briefly describe two different theories proposed by the narrator to explain why Venus might be rotating so slowly today.
1- Venus was smashed by a massive planetoid early and it slowed its rotation
2- tidal interactions of Venus with the sun slow down its rotation rate
From the video "Venus Could Have Supported Life for Billions of Years: "in the simulation described in the video, Venus is supposed to have started with a thick atmosphere of mostly Nitrogen and oceans of water all over the surface. What did the simulations show about the long-term evolution of Venus’ atmosphere over the first 3 billion years or so of its history (asking specifically about temperatures and carbon dioxide levels)?
The amount of radiation from the sun increased over time so today Venus receives twice as much solar radiation than earth does. Venus was able to maintain stable temperatures for three billion years and its thick atmosphere of CO2. Then, it cooled down and carbon was drawn out of the atmosphere and locked into silicate rocks.
From the video "Crash Course - Mars: "what is thought to be the cause of the huge difference in geography between the northern and southern hemispheres of Mars?
Mars suffered a tremendous impact from an object hundreds of kilometers across eons ago. It left behind a vast basin near the north pole of the planet, which filled with lava.
From the video "Crash Course - Mars: "describe the evidence that tells us that frozen water probably exists in many places just beneath the surface of Mars at mid-latitudes, not just at the polar caps.
Some recent small asteroid impacts have white area around them; underground deposits of ice splashed out by the impact. Some crater walls collapse a bit and have dark channels running down them, which look like they could’ve been carved by flowing water.
From the video "Crash Course - Mars: "why does the narrator argue that life could have potentially formed on Mars even before it formed on Earth, billions of years ago?
The Curiosity rover detected simple organic molecules in a rock sample which means that the ingredients for life were and are on Mars. It also detected a spike in methane, a gas that can be produced by life.
From lecture, describe how Earth's magnetic field (a) is formed, what ingredients are necessary for a planetary magnetic field and (b) protects us from the solar wind.
a- rotation & internal beat
b- earth's magnetosphere deflects solar wind; moving charges cannot easily cross magnetic field lines
From lecture, (a) what are two effects the solar wind can have on a planet unprotected by a magnetic field, and (b) how is each effect harmful to potential life on the surface of such a planet?
a- 1) When solar wind particles impact gas, it creates sterilizing radiation
2) causes atmosphere to fade away = sputtering
b- 1) radiation is deadly to life -> disrupts cells / proteins
2) escape velocity: gases in our atmosphere (w too much heat) can cause gases to escape; -> no water can exist, can’t breathe, also detrimental to life
From lecture, describe what causes the aurora (aurora borealis and aurora australis) close to each magnetic pole of the Earth.
Aurora borealis = north pole
Aurora australis = south pole
Cause: solar wind interacting with our atmosphere
From lecture, (a) briefly explain the fission theory for the origin of the Earth's moon. How does the fission theory explain (b) the lack of metal in the Moon relative to the Earth and (c) the fact that Earth and Moon rocks have very similar isotope fingerprints?
a- Earth was spinning so fast that pieces of earth formed a ring of debris -> resulting in the moon and then earth slows
b- It would be from earth’s mantle which is all rock and no metals
c- If moon came from earth so same isotopes, too
From lecture, briefly describe two problems with the fission theory for the Earth's moon (two reasons why astronomers today do not believe it is a valid explanation).
1- Volatiles: what got rid of them? Unanswered bc it would need to be hot
2- How did earth slow down by a big factor of 20 -> there would need to be a big force that slowed earth and there is none; no other planet spins as fast as earth presumably did in fission theory
From lecture, briefly describe the capture theory for the origin of the Earth's moon, and explain two problems with the theory from a scientific standpoint.
Capture theory: earth and moon formed independently; earth captures moon during close encounter
1- Earth's mass and how capture works: as moon falls into earth, it would go so fast it escapes. Object (moon) towards earth would need to slow down significantly -> moon Is too massive to slow down
2- Not believable that they’d have same isotope
From lecture, briefly describe the giant impact theory for the origin of the Earth's moon. How does the giant impact theory explain (a) the lack of metal in the Moon relative to the Earth, (b) the fact that Earth and Moon rocks have very similar isotope fingerprints, and (c) the relative lack of volatiles in lunar rocks compared to the Earth.
Giant impact theory: big object (like mars) crashes into the earth and knocks a piece of earth into space
a- Earths mantle is rocky -> lacks metal
b- Some isotopes fingerprint bc moon is a part of earth
c- Heating source from impact got rid of volatiles
From lecture, briefly describe the four major sources of gas in a planetary atmosphere.
Outgassing/volcanism/geysers/springs
Small impacts
Chemical reactions on surface
Evaporation
From lecture, briefly describe the four major sinks of gas in a planetary atmosphere.
Thermal escape
Solar wind stripping
Condensation
Chemical reactions on surface
From lecture, briefly explain why the Copernican Principle would lead us to believe the Earth and Venus likely had similar atmospheres originally.
Venus' atmosphere used to have an earth-like atmosphere
Copernican principle: we arent special so whatever process happened on earth is probably to happen somewhere else like Venus
Venus and earth formed same part of solar system w same mass and materials
From lecture, for each of the possible sinks of atmospheric gases (thermal escape, solar wind stripping, condensation and chemical reactions), explain why Argon does not leave an atmosphere but instead remains at a constant abundance over time for worlds like Earth and Venus.
Ar is heavy gas -> moves slowly
Ar sits at base of atmosphere
Noble gas so it doesn’t react with any other element
From lecture, explain how we use Argon to argue the Earth and Venus originally had similar atmospheres. Describe the logical sequence that starts with Argon measurements and ends with the conclusion that the two worlds had similar atmospheres originally.
Earth and venus have similar amount of Ar
Since Ar abundance doesn’t change over time, then earth and venus had similar amounts of Ar originally
If Ar was same originally, then so was “body” of the rest of the atmosphere
From lecture, explain two important differences between Venus and Earth that led Venus to lose much of its water vapor while Earth is not really vulnerable to this sort of effect.
Venus lacks magnetic field -> solar wind
Venus lacks oxygen and ozone layer -> UV lights
Solar wind and UV lights break apart h20 so h2 escapes
Runaway greenhouse effect
1) Venus is hotter
2) more h20 is evaporated
3) h20 is destroyed by UV and solar wind
4) w less h20 -> no c02 sinks
From lecture, explain why heavy water is enriched on Venus compared to the Earth.
Heavy water: higher % than light water on venus
Venus is depleted in normal water due to the mix of heavy and normal water topping normal water off its surface
From lecture, describe the evidence (3 parts) from the Magellan explorer that led scientists to the conclusion that Venus resurfaced itself somehow about 500 million years ago.
1- # of craters on venus = 5x earth; Venus’ surface is 500~ million years old
2- Crater distribution on venus is uniform not clustered; entire planet was resurfaced at same time
3- Crater appearance is pristine, no erosion; no gradual way to erase craters
from lecture, aside from the "runaway refrigerator" process from Q4.21, describe two additional ways that the Martian atmosphere may have been lost over time (and why each of these doesn't happen to Earth).
Thermal escape due to impacts
Mars has lower escape escape velocity
Mars is closer to the asteroids -> more impacts?
Solar wind stripping after mars loses it magnetic field
From lecture, explain (a) why Argon reconstruction cannot work on Mars and (b) the evidence that some Argon has managed to escape from Mars.
a- Argon can reach escape velocity so its not a reliable tracer
b- Lighter argon is more abundant and has been depleted
Note 
Flashcard (24)