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by: Stephan Kuvalis


Stephan Kuvalis

GPA 3.89


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Class Notes
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This 12 page Class Notes was uploaded by Stephan Kuvalis on Thursday October 29, 2015. The Class Notes belongs to ASTR 3300 at University of Colorado at Boulder taught by Staff in Fall. Since its upload, it has received 46 views. For similar materials see /class/231964/astr-3300-university-of-colorado-at-boulder in Astronomy at University of Colorado at Boulder.




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Date Created: 10/29/15
Water on Mars Today low pressure prevents liquid water from being stable on the surface but substantial reservoirs of water at the poles as ice and 2 in the subsurface was the water ever present as liquid for how long and how much role in shaping landforms on Mars is any liquid water present noW underground Evidence from orbit morphology of landforms from experiments on landers Alluvial fan in China running water standing water floods Progress in imaging Viking orbiters 25m per pixel maps Mars Global Surveyor 1 5 12m per pixel Mars Reconnaissance Orbiter 30cm per pixel V Dunes at the South Pole from HiFlSE imagery Channels on Mars Oldest Martian terrain contains channels similar to river systems on Earth up to 1 km wide and whole system up to 1000km long also very large outflow channels draining into the low northern terrain 103 of km wide teardrop shaped islands strongly suggestive of fluid flow Appearance of very old craters and lack of small streams argues against rainfall may be groundwater flow Some craters on Mars seem to have been formed from impacts into water rich terrain l gt Yufy crater 20km across Has an eje39cta blanket that appears to have flowed across the surface as if icy material was melted so the ejecta was fluid older crater that the ejecta seems to have flowed around EXlIZater r strial L ife springzwb A Martian ocean Morphology on the shoreline Was there an ocean on Mars quot Alana Complicated by large topographic changes in last few billion years l zoau man suuu mm 2m Juan awn ilkk lrv lnnilu woo Hum Perron eta 2007 5mm 41mg Sh EXbate xrestrial waspmeme Augusl 1959 September 2005 Changes in the appearance of some gullies Exlla39Ierlestrial er5ming2008 Transient water flows today Water today is not stable in liquid form on the surface but if released from underground reservoirs would flow some distance before freezing boiling off Evidence for such flows would suggest liquid water still exists in the sub surface possible abode for life Martian temperatures are generally very cold but can rise above freezing mate st al L ife springzootz Several instruments on board each rover that can analyze composition of soil and rocks Small grinding tool can clean rocks prior to analysis Mossbauer Spectrometer gamma rays excite resonances within nucleus of some atoms e g iron emitted gamma rays emitted srgnature depends upon lt composition and structure incident of the material gammarays Cmmvsl Basellm 1 BuiliMerlot Tarmac dentify jarosite and hematite from spectra taken on rocks near the landing sites Composrle HmASDIl Jarosite hydrous sulphate of potassium and iron On Earth requires presence of acidic water to form e g in mines Mars suggests presence of water for an extended period perhaps 2 e A 0 4 a 2 in a volcanic Spring fOHOWed EOBLMCKIMCLMIGGIERAT B by an arid epoch I l 4 1 4 x l v l 4 2 u 2 4 VEIOCHY mmS Exvaternst39rial Lite Sping Summary water on Mars Today significant volume of water locked up as ice and probably beneath the surface evidence for small surface flows that may be due to transient water Early Mars enough water to result in alteration of minerals likely extensive subsurface water ice extensive channels and possible ocean but the relative role of water and lava is not clear nor whether any water perSisted for long periods Mamtq d Life Spring f water has been lost from Mars where did it go Basic process dissociation of H20 by UV radiation in the Martian erecall no 03 sh39 39ng escape of the light hydrogen atoms to space oxygen reacted with rocks on the surface i 9 Lower gravity means that atmospheric escape occurs much more readily on Mars than Earth Mars may have had substantial amounts of liquid water for first bllllon years might have subsurface water today Extraterrestrial Life Lecture 7 Next homework Thursday To first approximation distance from star and luminosity of star determine the surface temperature and possibility for liquid water on surface Atmosphere greenhouse effect also plays an important role warms Earth by 20 degrees Celsius water vapor carbon dioxide methane increased concentration warms the planet Particulate matter dust from volcanoes cools Extraterrestrial LiferSpring 2008 Short term feedback processes Short term feedbacks are mostly positive destabilizing e g water vapor increased temperature leadsto more evaporation from the oceans increasing the atmospheric concentration of water vapor Water is a greenhouse gas so this is positive feedback Role of clouds Timescale essentially instantaneous Extraterrestrial Life Spring 2008 Long term feedback processes On longer timescales geological processes dominate Tiny fraction of the Earth s total CO2 reservoir is in the atmosphere tmosphere CO2 381 parts per million 39 ocean Extraterrstrial Life Spring 2008 s the climate stable over 39 39 39 time Feedback if the surface temperature rises does the concentration of greenhouse gases in the atmosphere increase possibly raising the temperature further Positive feedback decrease offsetting the rise Negative feedback Empirically expect negative feedback to prevail on the Earth but may be different for other planets Extraterrestrial Life Spring 2008 Extent of ice cover also affects the climate via changes to the mean albedo mu f Increased temperature leads 9 to less snow and ice fraction an of Solar energy that will be m 553W gymyss absorbed increases 5 Positive feedback so clnaus srnAms WT TImescale 1000s of years 4 my lCE Zn w IcHoPs tsAvnmA 7 SW IMEAmws WATER WM FORESY U Life Spring 2008 Volcanic activity can liberate CO2 from rocks and release Magma can be few by mass water Large eruptions release km3 to 1000 km3 of rock Mt Pinatubo Life Spring 2008 Estimate for the current volcanoes to atmospheric CO2 Timescale for significant changes to the atmosphere Expect volcanic activity to be important on timescales of the order of 104 years Carbon sinks n the atmosphere Weak acid in rain weathers silicate rocks yields bicarbonate becomes locked up in calcium carbonate shells from biological activity in the eans carbonates becomes locked up in the crust Same process can occur Without biological activity Carbonate silicate cycle Atm osph eric 602 rain fails if volcanism depends temperature Is on age size of too high planet etc Oceanic carbon Carbon in u k forms rocks which are man e we subducted via plate tectonics This is a negative stabilizing feedback loop warmertemperatures more moisture in the mosphere more rain greater rate of removal of COZfrom the atmosphere cooler temperatures less rain longer residence time for CO2 in the atmosphere Very long term changes in climate are driven by Sun s changing luminosity cyclical changes in the Earth s orbit l rotation different arrangements of the continents changes in volcanism life Despite these variations appears that the natural carbonate silicate cycle has been sufficient to roughly stabilize the Earth s surface temperature for several billion years but ice ages snovvball Earth episodes What are the limits to this stabilizing influence Magellan radar image of Venus Other planets Volcanoes on surface of Venus probably still volcanically active planet But water has all been evaporated by high surface temperature and lost into space Weathering aspect of the carbonate silicate cycle does not operate large concentration of C02 in the atmosphere Venus surface temperature is 464 Celsius Mars certainly d active Olympus Mons 27km high Summit of OfympusMons on MarsMars Express Mars active volcanism and plate tectonics appears to have ceased in distant past Small sizeof planet10 mass of Earth has allowed Mars to cool and plate tectonics has ceased Volcanic outgassing aspect ofthe cycle has been broken mplica ns for extrasolar habitab orlds Small planets39 without long term plate tectonics may not ablet maintain a habitable climate habitablezone for such planets may be much smaller l non existent What Is the typical mass ofterrestrial planets probably depends upon the mass of solid material less favors more smaller planets Solar System have two Earth mass planets around lower mass stars may be quite different Orion with Hubble Space Telescope Extraterrestrial Life Spring2008 Properties of protoplanetary disks Detect emission from hot T1000K dust in the infrared wavelengths of light longerthan visible Disks contain both gas and dust Do not directly detect larger solid bodies rocks asteroids planets Detect molecules such as CO and T ammonia from the gas in the disk Detect cool dust 0 100 K via radio emission at mm wavelengths 1 Fraction of JHKL Excess Sources 7 Disk litetime Look at young star clusters of different ages measure in each the fraction of stars that have intrared emission characteristic of hot dust in surrounding disks 00 l Nchznao Trapczlum l mm 1 1 mm M Nov 2254 lt syslemuo mm a o a c p o l i N5 232 m o x will 4 5 Age Myr c Find that the typical lifetime of protoplanetary disks is a few million years measure of the gas disk litetime Limits the timescale for gas giant tormation terrestrial planets could take longer Haisch Lada amp Lada Disk size at the distance of Orion about 1500 light years Hubble s resolution 1 pixel is about 50 AU This disk is tew hundred AU in radius much larger than the Solar System Smaller disks would not be directly detectable at this distance selection effect Ex ater restrial Life Spring 2008 Disk mass Can estimate the mass of dust from strength of the radio emission Typical disks have total masses gas dust between 0 1 Solar masses and 10393 Solar masses of which 99 is gas and 1 solid material disk mass dust to gas ratio This is about 30 Earth masses of dust enough to form planets Extraterrestrial Life Spring2008 Minimum mass Solar Nebula How much gas must there have been in the disk around the Sun to form the planets estimate the mass of iron in each planet calculate how much gas would need to be added to dilute the iron to the same tractional abundance as in the Sun Summing up over the planets get about 0 01 Solar masses of gas Life Spring 2008 Extraterrestrial Life Spring 2008 How was that mass distributed with distance from the Sun take the augmented mass for each planet imagine spreading the gas out into a rings that fill up the space between the orbits of the planets divide mass by area of the rings to get a surface density of gas kg per square meter Venus Eanh Mars Extraterrestrial Life Spring 2008 Disk composition gas in the disk will be mixed with dust small particles of graphite silicates etc additional solids can condense from the vapor At a particular temperature and density there is a most stable mix of chemical species which is what will form in the disk given enough time for chemical reactions eg T 1400K MgAIZO4 spinel T N 150K water ice T 50K methane methane ice condensation sequence 39 I quot Spring2008 pressure liquid water Ice triple point at 0006 I atmospheres pressure temperature Note T N 150K not 273K because of low pressure This means the snowline is generally well beyond 1AU the water on Earth did not condense in situ 39 Life Spring 2008 nterred surface density falls off with distance with a gap in the location of the asteroid belt Gas was dense close to the star raretied further away l I la ID AU Fig r n y th39 rcxukmg mm mmugn cantigunu Imus surrounding Ilicir orbits quotlbw manning ol39rlh 39crrur bm39 I discussed m mu Kc Weidenschiling 39 Life Spring 2009 Most important boundary occurs at T N 150K above 150K rocky materials but no ices below 150K rock and ice initially water ice but ice dominates Location in the disk where T 2 150K the snowline gas rocky gas rock ices materials snowline r few AU Extraterrestrial Life Spring2008 Observations of the asteroid belt suggest that inside about 2 7 AU asteroids are typically made of minerals that are water poor outside 2 7 AU water rich minerals are relatively common Probably the snow line in the early Solar Nebula was at a few AU in the middle of the present day asteroid belt 39 Life Spring 2008 Why is the snowline important 1 Water habitability Oxygen and hydrogen are abundant elements Just beyond the snowline surface density of ice rock that forms is fador 4 greater than the surface density of rock only just inside the snowlin Greater density of solid material promotes more rapid planet formation why we can fo 9 s iants in the outer Solar System but not in the inner Solar System Saturn system Gas giant smaller than Jupiter about 95 Earth masses rings extend from 6 000 120 000 km above the equator of Saturn made up of mostly small icy particles orbital radius is 9 6 AU planet formed in a still colder part of the protoplanetary disk in which hydrocarbon ices as well as water ice were present 39 Life Spring 2008 Satellites of Saturn Large number 60 moons Enceladus 500km diameter moon orbital radius 240 000km Titan 5150km diameter second largest moon in the Solar system after Ganymede orbital radius 1 2 million km orbital period Saturn 16 days orbital period of Saturn 30 years Solar flux 1 of value at Earth Temperature in absence of greenhouse effect 80K Both satellites are of interest for astrobiology Enceladus possible existence of liquid water in the subsurface plumes mean that it is easily accessible to measurements Titan no evidence for liquid water but many similarities to the early Earth may provide information on the chemistry that preceded lite on Earth The ESA Huygens probe landed on Titan early in the Cassini mission 39 Life Spring 2008 Atmospheric properties Titan atmosphere Dense atmosphere extends several hundred km high Surtace pressure is 1 5 times Earth pressure surface temperature 90K PocpT 1 5 times higher than Earth 3 tImes lower than Earth 90K rather than 300K Solving density at Titan s surface is about 5 times the terrestrial value 39 Life Spring 2008 P39quot between Titan and 39 Jovian moon Ganymede is similar in size to Titan but has no atmosphere Temperature in the protoplanetary disk Jupiter water ices Saturn hydrocarbon ices Appears Titan started with a large reservoir of material that can survive in modified form in the atmosphere for a long time 39 Life Spring 2008 Extraterrestrial Life Spring2008 Atmosphere 98 nitrogen N2 2 methane CH4 small amount of H2 Atmospheric haze is due to I hydrocarbons literally smog l A nterpretation methane and ammonia NH3 released from the surface are broken up in the high atmosphere hydrogen escapes whereas N2 is retained Short lifetime of CH4 10s of millions of years in the atmosphere suggests reservoir lakes seas ocean 39 Life Spring 2008 Cycle with methane and other hydrocarbons playing the same role that water does on the Earth Atmosphere largely obscures Titan s surface in the optical or infra red surtace maps from Cassini s radar and from camera on the Huygens probe Radar image colored to emphasize smooth areas of terrain near the pole these may be lakes of hydrocarbons Release of carbon in the upper atmosphere from destruction of methane leads to formation of heavier organic compounds which then rain out of the atmosphere Low sunlight means desert like conditions lots of methane in the atmosphere but 1cm precipitates out per year Ex atelrestrial Life Spling2008 Ex atenestrial Life Spring 2008 River channels Surtace trom Sand dunes an altitude of mpact craters about 10km Lakes durIng the Huygens probe descent Topography looks Dry river quite a lot like channels Earth No very clear sign of volcanic activity Ex aterreshial SplingZOOB View from the surface dry Liquid water at the Huygenslanding site No evidence for liquid water much too cold on the With Icy pebbles surtace Atmosphere contains simple molecules HCN CZHG polymers of quite uncertain make up tholins maybe polymers of HCN Speculations subsurtace lakes or oceans heated by internal heat from radioactive decay liquid water in volcanic hotspots transient 1000 years water in regions heated by impacts Gas phase reactions seem to occur at high altitude with condensed materials in the lower atmosphere and on the surface Unless life without water is possible seems unlikely that conditions for habitability are satisfied on Titan 39 Life SpiingZOOB Extraterrestrial Life Spring2008 Pre biological chemistry n increasing complexity simple organic molecules complex molecules polymers amino acids replicating molecules lite First three are either detinitely present probable opportunityto study these processes on another world on Titan or seem Exbaterrestrial Life Splinng Future exploration possibilities Numerous more Cassinitlybys 4 candidate tlagship missions to the outer planets Europa orbiter Jupiter orbiter Enceladus orbiter Titan explorer Titan proposal includes an orbiter a lander and possibly a balloon to studythe surface chemistry in detail t selected launch from 2015 onwards Ex ateirestrial Life Spring 2008


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