PYTS/ASTR 206 – Mars: Recent History1z AnnouncementsUPi kSh TAUse Priyanka Sharma as TA [email protected] Office hours: Tuesday 10.30am-12.30pmRoom 316, Kuiper Building Thursday office hours? Can only stick around for ~1 hour today …but these office hours are under-utilized in general Do away with these hours? Calculate your expected grade… Add HW1 and HW2 percentages together, multiply by 0.15Addthetwoinclass activity marks (out of 5) together multiply by 2Add the two in-class activity marks (out of 5) together, multiply by 2 Take your mid-term score (out of 45), multiply by 1.111 Add these three things together…. And compare to grade table This is a REALLY rough guess, you can easily move up/down a gradePYTS/ASTR 206 – Mars: Recent History2Mars – Recent HistoryPTYS/ASTR 206 – The Golden Age of Planetary ExplorationShane Byrne – [email protected]/ASTR 206 – Mars: Recent History3In this lecture…In this lecture…Martian weather todayzMartian weather today Seasonal frost Ice clouds Dust stormsz Recap Ancient Mars Transition to cold dry conditionsGiant FloodszGiant Floods Outflow channelsz Climate change on Mars Polar ice capsp Orbital variationsz Running water today? GulliesFl i iFlowing icez Volcanism and life? Methane in the atmospheremsss.comPYTS/ASTR 206 – Mars: Recent History4Current ClimateCurrent Climatez Mars has seasonal ice capsz Mars has dust-storms Dry dusty southern summer Warmerz Mars has water ice clouds Wetter northern summer coolerPYTS/ASTR 206 – Mars: Recent History5z Earth-like seasons – but with a twistM ti bit i t i ( t i it 0 1)Martian orbit is eccentric (eccentricity ~ 0.1) Mars is farther from the Sun in the northern summer (1.37 AU) Closer in the southern summer (1.67 AU)Northern SummerCoolerLongerSouthern SummerHotterShorterMore water vaporMore cloudsLess water vaporMore dust stormsPYTS/ASTR 206 – Mars: Recent History6z Mars has a similar obliquity (25°) to the Earth. Ensures seasons with periods of permanent polar darkness and daylight.pp p ygz Mars has a low pressure CO2atmosphere. Permits seasonal icecaps of CO2ice to form -Leighton and Murray (1966)PYTS/ASTR 206 – Mars: Recent History7z Not every part of the ice cap is frostyLow albedo region inside the COcapLow albedo region inside the CO2cap Spectral indicators of large grain size Large areas anneal into a transparent slab in 100’s of daysPYTS/ASTR 206 – Mars: Recent History8z Behavior of a transparent slab of CO2iceCO2icePSP_002675_0945__z Multiple fan (wind) directionsScouring of channels tozScouring of channels to produce ‘spiders’PSP_002533_0935PYTS/ASTR 206 – Mars: Recent History9z Clouds are commonIth thIn the northern summer… Especially over volcanoes Lifting of air over obstacles cause water to condensecondensePYTS/ASTR 206 – Mars: Recent History10z Dust StormsRi ldtt i thRegional dust storms common in southern summer Global dust storms occur every few years Reasons for interannual variability not well understoodReasons for interannual variability not well understoodPYTS/ASTR 206 – Mars: Recent History11How Mars became cold and dryHow Mars became cold and dryz The Tharsis volcanic bulge formed Thick (>8 kilometers thick) sequence of volcanic rockszOutgassing of a lot of volcanic gas changed the climatezOutgassing of a lot of volcanic gas changed the climate Warmer conditions allowed more liquid waterPYTS/ASTR 206 – Mars: Recent History12Earth, Venus, MarsMars, EarthCO2and water EarthRocks recycled by plate tectonicsMarsRunawayRock cycleAll start with CO2and water in their atmospheregoes into rocksVVMarsNo plate tectonics–CO2stuck in rocksRunaway icehouseatmosphereVenusWater not stable as liquidVenusCO2stays in atmosphereRunaway greenhousePYTS/ASTR 206 – Mars: Recent History13z There’s just one problem We can’t find these CO2bearing rocks (carbonates) Some recent progress on this… Spectral evidence of carbonates discovered and announced 2 months agoPYTS/ASTR 206 – Mars: Recent History14z Mars at the end of the warm periodMb ?Maybe an ocean? Some evidence of former shorelines – but this is still controversialPYTS/ASTR 206 – Mars: Recent History15z Former shorelines should be all the same elevationthe same elevation “sea-level” on Mars One shoreline matches this…z Shorelines have been altered By subsequent volcanoes By polar wanderHead et al., 1999PYTS/ASTR 206 – Mars: Recent History16Early greenhouse atmosphere quicklyA Changing PlanetzEarly greenhouse atmosphere quickly removed Warm-wet transition to cold-dryHaberle, 1998Lt ffl ilLots of fluvial erosionNot much fluvial erosionPYTS/ASTR 206 – Mars: Recent History17Giant floods…Giant floods…z Mars starts to freeze From the surface downwards Ocean starts to freezez Cryosphere forms Ground is frozen to some depthp Cryosphere gets thicker as planet gets colderCliff d d P k 2001 Groundwater exists between cryosphere and basementClifford and Parker, 2001PYTS/ASTR 206 – Mars: Recent History18z What happens next?No ice covered ocean in the northern lowlands todayNo ice covered ocean in the northern lowlands todayCliff d d P k 2001 Ice is transferred to the polar regionsOcean goes awayClifford and Parker, 2001Ocean goes away Groundwater system fills upPYTS/ASTR 206 – Mars: Recent History19z Accidents can happenpp Cryosphere could break Ground water can flood outClifford and Parker, 2001PYTS/ASTR 206 – Mars: Recent History20z Outflow channels on MarsGround water outbreaks-Carves huge flood channelsGround water outbreaks -Carves huge flood channels Floods 100’s of meters deep at ~25 m/s Discharge rates of ~ 107m3s-1 Enormous by terrestrial standards!!y Mississippi river ~ 3x104m3s-1PYTS/ASTR 206 – Mars: Recent History21z Terrestrial analogueEnd of the last iceageEnd of the last ice-age Glacial lake Missoula- Ice-dam breaksChanneled scablands, WashingtonOutflow channel, MarsPYTS/ASTR 206 – Mars: Recent History22Ab t 20% f th i f th G l d ihtClimate change and ice capsClimate change and ice capszAbout 20% of the size of the Greenland ice-sheet1.2 million km31.1 million km3PYTS/ASTR 206 – Mars: Recent History23z Orbital changes create layersEarth’s obliquity variationLaskar et al., 2003Putzig et al. 2008PYTS/ASTR 206 –
View Full Document
Unlocking...