November 17, 2016 AST 101: Professor Freeman Lecture: Atmosphere: Mercury, Earth, Mars, and Venus Textbook Pages: 171-202 Lecture Tutorials: 105-110 ∙ How did we get from there to here? o The Greenhouse Effect ∙ A few things to keep in mind o Asteroids: any unprotected object gets hit repeatedly in an ongoing process (more in early solar system, but the universe is full of ‘em) o Our atmosphere is thick enough to burn up many, but not all asteroids: big ones don’t melt fully o Volcanism ▪ Hot rocks melt ▪ Molten things flow ∙ On Earth, there is a thin layer of rock and water over a molten mantle. This mantle is what is expelled upward during a volcanic event and this is why lava/magma flows ▪ If the core of a planet is hot, it has volcanic activity ▪ Radioactive decays of uranium sustain internal heat of planets over billions of years by keeping the core warm
In the past
▪ What happens if you have an atmosphere that reflects IR, but not visible light?
∙ What in Hell (literally) happened?
∙ How did we get from there to here?
N2; 02; C02; H20
C02; N2; Ar
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We also discuss several other topics like What does the industrial light and magic do?
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Don't forget about the age old question of What are some known policies towards monopolies?
∙ Interpreting o 1 atm; one Earth’s atmosphere’s worth of gas o Don’t memorize the above, just get a general idea of the relationshipso The Δ Temp refers to the change from the actual temperature to the predicted temperature ∙ Mercury o The fleet messenger god, whizzing around the Sun… o Agile, lively Mercury... o Surface is pockmarked with craters. ▪ It clearly has been hit by asteroids ▪ It didn’t have an atmosphere when this happened ▪ No weathering, geologic activity, or the like has taken place since ∙ If it did occur, this would reform the surface of the planet ∙ Having an atmosphere means having wind, which implies weathering, so it doesn’t have an atmosphere, either. ▪ It’s actually a dead rock. ▪ Though interesting, if you like rocks. ∙ Mars o The cruel god of war… o Bloodthirsty, violent Mars… o We’ve sent robots to Mars that have explored it in some detail ▪ Rocks with rust in them, making it red ▪ Only a thin atmosphere (mostly CO2) ▪ Large volcanoes (Mt. Olympus), none active ▪ Evidence of interior heat, but not like Earth and Venus ▪ Evidence that liquid water once ran on its surface ∙ Channels/riverbeds ∙ Ocean basin ∙ Icecaps ▪ Evidence that it once had an atmosphere of water and CO2 ▪ Evidence that it was once much warmer than it is today ∙ A thicker atmosphere as well, which would account for the heat. ▪ …what happened? It’s obviously a changed planet… o Life on Mars? (interlude) ▪ At the same time as Earth? ▪ If we find bacteria on Mars, one of two things… ∙ 1. Totally alien, completely different than life on Earth, which arose separately ∙ 2. Stuff in common with Earth… o Maybe there was spaceflight; asteroids and comets may have transferred material o Maybe…. Just maybe… ▪ We are Martians and colonized earth ▪ We colonized Mars o Rusty, peaceful Mars… (back to business) ▪ Something happened around three billion years ago ▪ Mars lost its atmosphere∙ Decline in interior heat ???? less volcanism? ∙ Solar wind stripping the atmosphere away? ∙ Loss of magnetism? ∙ Still an area of very active research ▪ This caused it to cool (no more greenhouse effect) ▪ Now Mars’ surface mainly contains memories… ∙ …and robots! o Because, “we are kind of squishy and vulnerable and not very good at space travel” o Mars, the robots’ domain… ▪ NASA sent two lil robots, named Spirit and Opportunity, which were supposed to last 90 sols ▪ Spirit: stuck after 2274 Martian days ▪ Opportunity: still going strong after 4500+ Martian days ∙ Venus o The goddess of love and beauty… o Beautiful, lovely Venus… ▪ The surface temperature is hot enough to melt lead ▪ It rains sulfuric acid ▪ The atmospheric pressure is enough to crush your skull ▪ …if there is a Hell in our solar system, it is Venus. ∙ What in Hell (literally) happened? o Horrifying, poisonous Venus… ▪ Visible light doesn’t go through this atmosphere well ▪ …radar does! ▪ We’ve used radar to map the Venusian surface ▪ It has some interesting geology ▪ You can read about it in your book ∙ Earth o Cradle of life… ▪ The thing that’s weird about Earth is… well… everything. o Our home… ▪ Active volcanism throughout its history ▪ Large amounts of liquid water on surface ▪ Stable climate: most of surface between 273 K and 373 K (freezing/boiling) for a long time ▪ Atmosphere with significant oxygen, nitrogen, some CO2 ▪ Surface covered by self-replicating, reactive, diverse, beautiful, aware machines, made of carbon compounds: life! ▪ Atmospheric oxygen from the byproducts of plant metabolism ▪ Hot core generates a magnetic field that shields atmosphere from solar wind o Our large Moon… ▪ The Moon appears to have similar composition to Earth ▪ …but it lacks active geology or an atmosphere▪ Shortly after the formation of Earth, something the size of Mars hit us ▪ Some of the resulting fragments broke off and orbited the Earth ▪ They coalesced into the Moon ∙ The greenhouse effect o Planet’s temperature set by radiation balance/ozone layer: thanks plants! ▪ Incoming thermal radiation from the Sun – visible ▪ Outgoing thermal radiation from planet -- infrared ▪ What happens if you have an atmosphere that reflects IR, but not visible light? ▪ The outgoing thermal radiation is greatly reduced! ∙ Since some thermal radiation can’t come out and is trapped ▪ This is called the greenhouse effect ∙ Δ Temp: greenhouse effect o Venus has a tremendously thick atmosphere and a powerful greenhouse effect ▪ Its atmosphere contains a great deal of CO2, which reflects IR strongly ▪ The thermal radiation that would carry heat away from Venus can’t get out ▪ It is over 400 K hotter than was predicted o Earth has a thinner atmosphere ▪ Nitrogen doesn’t absorb strongly at any relevant wavelengths ▪ H20 and C02 are strong greenhouse gases, but they are only a bit of the atmosphere ▪ We are about 20 K warmer than predicted ▪ These gases are very important for determining Earth’s temperature ∙ Additional o Volcanoes and earthquakes (seismic waves) are not the only processes acting to reshape Earth’s surface, nor the most dramatic. Far greater change can occur on the occasions when an asteroid or a comet slams into Earth, and constant, unrelenting flow of rivers, wind, rain, and ice can change the Earth as well o All five terrestrial worlds (including the Moon) looked very similar when they were young, but the differences are because of changes occurring through time o Terms ▪ Core: The highest density material, consisting primarily of metals such as nickel and iron, resides in a central core ▪ Mantle: Rocky material of moderate density—mostly minerals that contain silicon, oxygen, and other elements—forms a thick mantle that surrounds the core ▪ Crust: The lowest-density rock, such as granite and basalt (a common form of volcanic rock) forms a thin crust, essential representing the world’s outer skin ▪ Lithosphere: an outer layer of cool, rigid rock ▪ Differentiation: how gravity pulls denser material to the bottom, driving the less dense material to the surface o Interior heat ▪ The primary driver of geologic activity▪ Convection: the hot material gradually expands and cools as it rises upward, while cooler material from above gradually contracts and falls. On Earth, this happens very slowly ▪ Larger planets retain internal heat much longer than smaller ones, and this heat drives geological activity ▪ Is responsible for magnetic field , which creates the magnetosphere that acts as a protective bubbles surrounding Earth, shielding Earth’s surface from the energetic, charged particles of the solar wind, which would otherwise strip away atmospheric gas and cause genetic damage to living things ∙ The magnetosphere is also responsible for the aurora borealis o Processes shaping a planet’s surface ▪ Impact cratering: the creation of bowl shaped impact craters by asteroids or comets striking a planet’s surface ∙ Can also be used to determine the geologic age of any surface region from its number of impact craters (the more craters, the older the surface) ▪ Volcanism: the eruption of molten rock, or lava, from a planet’s interior onto its surface ∙ Tends to form mountains ∙ On Earth, though, water and gases became trapped beneath the surface, and volcanic eruptions released this gas into the atmosphere (outgassing) ▪ Tectonics: the disruption of a planet’s surface by internal stresses ∙ Tectonics and volcanism both require internal heat and therefore depend on a planet’s size ∙ Plate tectonics; unique to Earth as far as we know, as the lithosphere is fractured into a number of pieces ▪ Erosion: the weathering down or building up of geological features by wind, water, ice, and other phenomena of planetary weather ∙ Can break down and build up geological features o Atmosphere and ozone protect Earth from UV and X-rays o Greenhouse gases: gases that are particularly good at absorbing infrared light. Water vapor, carbon dioxide, methane. o Geological features of the Moon ▪ Lunar maria: regions of the moon look smooth and dark, look a bit like oceans when seen from afar, hence the name ∙ Made by floods of lava billions of years ago, when the Moon’s interior was heated by radioactive decay o Geological features of Mercury ▪ Impact craters are everywhere ∙ Less crowded together than the craters in the oldest parts of the Moon, which suggest that molten lava covered up some of the craters that formed on Mercury during the period of heavy bombardment. Lava flows occurred most likely when the heat from radioactive decay accumulated enough to melt part of the mantle ∙ Largest impact craters called basins ∙ Some crater floors appear to be releasing easily vaporized materials from rock, causing rock to crumble and make pits nicknamed “hollows”, which leaves behind a light-colored coating whose composition remains unknown. This is weird ∙ Ice in permanently shadowed craters near Mercury’s poles, which probably came from impacts of comets ∙ Planet seems to have shrunk long ago, leaving behind long, steep cliffs. This is also weird. o Mars had active volcanism in the past, and its surface is dotted with numerous large volcanoes, which may erupt someday o Ice found on Mars, dried up riverbeds and other geologic features support this fact o Venus shows features of volcanism and tectonics, remains geologically active o Venus has a lack of plate tectonics, but this may be because Venus has a thicker, stronger lithosphere than Earth o Venus retains carbon dioxide in its atmosphere because it lacks oceans to dissolve the carbon dioxide and “lock it away” in rock o Venus has large, circular coronae that were probably made by hot, rising plumes of mantle rock o Earth has remained hospitable for billions of years because its climate is kept stable by the natural action of the carbon dioxide cycle o Human activity is rapidly increasing the atmospheric concentrations of greenhouse gases, causing the global average temperature to rise ▪ …next time…November 29, 2016 AST 101: Professor Freeman Lecture: Anthropogenic climate change/Climate change: in depth Textbook Pages: 213-254 (…this is for Jovian planet/Kuiper Belt stuff… not sure why this is here) Lecture Tutorials: 105-110 ∙ Most important scientific and political issue of our lives ∙ Most important class of this course ∙ Has potential to greatly change our world ∙ Review: the greenhouse effect o History ▪ What is the history of Earth’s climate? ▪ What processes caused it to vary? ▪ How do they affect each other? o The Anthropocene: the era of human influence on geology ▪ In an eyeblink, a drastic jump in atmospheric CO2: ∙ Evidence that this is already causing warming ∙ Evidence that this has the potential to cause for more warming o Consequences ▪ Exaggerated effect in the Arctic ▪ Sea level rise ▪ Disruption to society ▪ Ecological shocks and extinctions o What do we do about this? ▪ What are the sources of CO2 emissions? ▪ Who are the sources of CO2 emissions (spoiler: us)? ▪ Electricity generation ▪ Transportation ▪ Obstacles, legitimate and otherwise ▪ Positive signs ∙ The greenhouse effect o UV doesn’t go through because of O2/O3 o Visible light has a “hole” where it can go through o Outgoing IR radiation = incoming solar radiation o CO2 and H2O on the rise: the infrared light can’t get out and warms the earth: the greenhouse effect o Venus has a hugely thick atmosphere and powerful greenhouse effect ▪ Great deal of CO2, which reflects IR strongly ▪ The thermal radiation that would carry heat away from Venus can’t get out▪ It is over 400 K hotter than was predicted o Earth has a thinner atmosphere ▪ Nitrogen doesn’t absorb strongly at any relevant wavelengths ▪ H2O and CO2 are strong greenhouse gases, but they are only a bit of the atmosphere ▪ We are about 20 K warmer than predicted ▪ These gases are very important for determining Earth’s temperature! o The level of greenhouse gas is important for the planet ∙ Variation of Earth’s climate o Earth has seen quite a lot in its lifetime o The past state of Earth can help us study what the future may hold. o Graph Interpretation (see power point) ▪ The “flat” part is human civilization/human evolution ▪ 20,000 years: most recent ice age. Low parts are repeating ice ages ∙ “5 degrees is the difference between wooly mammoths in Georgia to now” ∙ Sea level lower, land bridge between Russia and Alaska ▪ Greenhouse effect changes during the year: 65 million years ago there were dinosaurs and it was 25-10 degrees Celsius cooler ▪ Very hot Earth/very cold Earth ▪ The problem with human climate change is that it is very rapid ∙ +12 to -4 was 100 million years ∙ Human climate change is 100 years ∙ Temperature difference compared to 20th century average o -33 C: complete lack of greenhouse effect o -10 C: “snowball Earth”; glaciers cover entire planet except for a small band at the equator o -5 C: ice age, Syracuse covered in glaciers o 0C: our familiar climate o +5 C: ??? (maybe our future) o +10 C: like the time of the dinosaurs, inland seas common, much of Earth underwater ∙ What process is most driving these fluctuations in climate? o Solar output: fluctuates in 11 year cycles but creates only 0.2-degree change, so no o Changes in volcanism might affect something over billions of years, not hundreds or millions o Earth goes through two cycles: cyclical changes in Earth’s orbit and tilt, which are what caused the series of ice ages o And, the industrial revolution is “just the last eyeblink of history” ∙ Positive and negative feedback o “Go further in that direction or go back to what it was” o If the Earth warms, then… ▪ Certain effects will cause even more warming: positive feedback ▪ Other effects will slow that warming down: negative feedbacko Positive feedback: snow. White snow absorbs less heat than dark soil, which is why snow piles take so long to melt o Negative feedback: oceans. More CO2 in air ???? oceans absorb faster, bringing CO2 levels down slowly ▪ Important to think about: does more carbon = warming, or does warming = more carbon? Or both? o In the short term, the positive feedback mechanisms win out. This means that small changes in the climate are amplified. o CO2 strongly correlated with temperature (positive feedback.) o Any way to demonstrate cause and effect? o What if we change CO2 on our own? What about Earth’s climate response? ▪ We don’t know. ▪ But it probably won’t break Earth’s climate forever. Maybe a few million years at the absolute most (maybe tens of thousands of years at most is more probable) ▪ Nor will we end up like Venus ∙ The current state o CO2 level close to 400 ppm and climbing (having exceeded 400 ppm briefly) o Industrial Revolution released this in a geological blink of an eye. ∙ This happened once before… o The “Paleocene-Eocene Thermal Maximum” was a sudden release of carbon dioxide 56 myr ago. Where from? Who knows. ▪ Something caused rapid release of CO2 over 2 thousand years at a peak rate of up to 6 billion tons/year ▪ Caused spike of 5-8 C that lasted many thousands of years ▪ The oceans absorbed much of this carbon as carbonic acid, bleaching coral ▪ There was a mass extinction of deep-ocean life and large changes to surface life ∙ What’s going on now? o We’ve warmed by about a degree Celsius o Sea level up by 15 centimeters ∙ And, yeah, this is our fault. o Unprecedented in at least the last 800,000 years ∙ Positive feedback o A warming Earth will set into motion other processes that accelerate warming ▪ Melting of ice, darkening the surface so it absorbs more sunlight ▪ Increased amounts of water vapor in the air ▪ Melting of permafrost in Siberia, which has a great deal of trapped methane ▪ (Water vapor and methane are also greenhouse gases) ▪ ???? Earth processes will magnify any effectsf rom human CO2 emissions ∙ What about the future? o Some further amount of warming is inevitable (precautionary principle). How much depends on how much more carbon we release into the atmosphere ∙ What climate change is and is not o Climate change is a moderate, overall warming of the planet by a few degrees.o It does not mean an end to cold weather: and cold weather does not mean that climate change is not happening o The world will have more hot extremes and fewer cold ones, but there is a difference between weather and climate ∙ Effects on the Arctic o The effects of current and future warming focus on the Arctic o Melting Arctic ice will have catastrophic effects on the Arctic ecosystem o All that water must go somewhere ∙ Sea level rise o Heat also causes the oceans to expand. The Marshall Islands may cease to exist. Miami, New Orleans, Manhattan ∙ Other ecological effects ∙ Effects on humans o Our societies are adapted for certain weather patterns and coastlines o People are going to have to abandon central cities like Manhattan and Miami o Overall warming will render a lot of marginal land unfarmable in Africa o Seasonal rainfall patterns that equatorial farmers rely on may change o Extreme weather events may become more likely, including droughts and storms o This is going to be expensive and result in disruption and maybe death for some ∙ Sources of CO2 emissions o Most come from fossil fuels for electricity, power vehicles, and in industry o The global wealthy are doing it ∙ Globalization means that countries now specialize in different things o Many wealthy countries (USA, France) are moving away from industrial economies (“Rust Belt”) o Middle-income countries are industrializing, with many of their products exported o Assigning blame on increasing Chinese CO2 emissions as a driver of climate change misses a big part of the story o In a global economy, this is a global problem o Some arguments: ▪ Not fair for West to have burnt coal already but India and China can’t benefit the same way ▪ But things are different now, CO2 is evil, coal stays in the ground for India and China ▪ “Climate debt”: West owes poor countries payment for past emissions to help GDP growth ∙ So, what do we do? ∙ Electricity generation o Electrical power is the largest source of CO2 emission o Coal: cheap and easy, but emits lots of CO2 o Natural gas: rapidly becoming cheap (fracking) and emits roughly half the CO2 o Zero-emissions power sources ▪ Hydropower: Cheap, but not always available, and disrupts rivers ▪ Nuclear: Large startup cost, more expensive than coal/gas but reliable and clean▪ Geothermal: Cheap where it is, clean ▪ Wind: More expensive and fickle ▪ Solar: More expensive ∙ Transportation o Cars – getting better, still wasteful o Buses – great in cities (“bus rapid transit”) o Trains – great if you have the transport density o Bicycles – the most efficient transport in existence o Airplanes – long distance fast travel is very hard o Steps forward: ▪ Continual gains in efficiency: smaller/better cars, hybrid cars/buses ▪ Electrification of everything: electric trains, electric cars/lorries ▪ Improve mass transit access and desirability ▪ Bus lanes in cities ▪ Rail/air balance for long haul travel is hard ∙ Avenues for climate change mitigation o Ban things like coal or inefficient cars: simple, but sledgehammer o “Cap and trade”: need a permit to burn fossil fuels. Society decides to what extent to limit CO2 and auctions that many permits: market forces determine how best to use them o Carbon tax: Similar idea, where market incentives drive down carbon use ∙ Obstacles o “Regulatory capture” of government by fossil fuel industry o Organized campaign of misinformation o Manufactured controversy ▪ The overwhelming scientific consensus stands behind climate change ▪ But well-funded skeptics can speak with a loud voice ▪ And the media, desiring balance, gives them disproportionate impact