Slide 1Mars – Early HistorySlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37PYTS/ASTR 206 – Mars: Early History1AnnouncementsUse Priyanka Sharma as TA[email protected]Office hours: Tuesday 10.30am-12.30pmRoom 316, Kuiper BuildingPYTS/ASTR 206 – Mars: Early History2PTYS/ASTR 206 – The Golden Age of Planetary ExplorationShane Byrne – [email protected] – Early HistoryPYTS/ASTR 206 – Mars: Early History3In this lecture…In this lecture…IntroductionComparisons to EarthSeasons on MarsEarly ideasSpacecraft explorationNot Earth-like after allFamiliar landformsEarly Martian HistoryCrustal dichotomyLarge impacts and volcanic activityMagnetic fieldsValley networksPYTS/ASTR 206 – Mars: Early History4One of the larger terrestrial planetsIntermediate between Mercury/Moon and Earth/VenusIntroductionIntroductionPYTS/ASTR 206 – Mars: Early History5Comparison to the EarthA mini-Earth?MarsSize 53% of the EarthMass 11% of the EarthDensity 3934 kg m-3(Earth/Venus ~ 5500 kg m-3)Solar Distance 1.52 AUYear 687 days, 1.9 Earth yearsObliquity 25°(Earth = 23½°)Rotation period 24hrs 37 minutes(Earth = 1 day)Surface Earth-like rocks and landformsSome parts heavily crateredRoughlyThe SameInternalStructureDays andSeasonssimilarto theEarthSimilarSurfacePYTS/ASTR 206 – Mars: Early History6Comparison with the Earth IIHow much solar radiation does Mars receive?Remember:Mars is 1.52 AU from the Sun: R=1.52So:Solar power at Mars is 592 W m-2 (about half that of Earth)Mars is a much colder place…Harder for liquid water (& life) to existNot always the case though… Early Mars was quite differentSolar power = 1367 W m-2 / R2Solar power = 1367 W m-2 / 1.522PYTS/ASTR 206 – Mars: Early History7Differences from the EarthMarsAtmosphere Mostly CO2 (Earth = Mostly nitrogen)Pressure 0.006 bars(Earth = 1 bar)Surface Temp. 200K(Earth = 300 K)Clouds Water ice and dust(Earth = water vapor)Magnetic field None(Earth has a strong field)Seasonal ice Carbon dioxide(Earth has water frost)VeryDifferentAtmospherePYTS/ASTR 206 – Mars: Early History8Early telescopic observations showedSeasonally advancing and retreating ice capsMars obliquity is similar to the Earth25° vs. 23½°Seasons on MarsSeasons on MarsPYTS/ASTR 206 – Mars: Early History9Mars has similar seasons to EarthMars has similar day/night cyclesMars has seasonal ice that comes and goesMars has changing patterns on the surfaceSeasonal vegetation growth? Unfortunately not…PYTS/ASTR 206 – Mars: Early History10Early telescopic maps were pretty crude…Giovanni Schiaparelli made maps with ‘channels’ (Canali in Italian)PYTS/ASTR 206 – Mars: Early History11Percival Lowell made many telescopic observations of MarsTranslated Canali as CanalsPopularized a vision of Mars that was inhabited by intelligent life Changing marks of the surface were vegetation “Canals” were transporting water from the polar caps to the equatorPYTS/ASTR 206 – Mars: Early History12Mariner 4 was the first spacecraft to visit Mars… July 1965Flyby mission -PYTS/ASTR 206 – Mars: Early History13What did Mariner 4 see?First planetary (non-lunar) mission to carry a cameraCratersNot good for lifeA very thin atmosphereNot good for lifeNo protective magnetic fieldNot good for lifeLooked pretty much like the MoonDisappointing…Dry, cold, dead….PYTS/ASTR 206 – Mars: Early History14The best-explored planet! (apart from Earth)1960’s1970’s1990’s2000’sPYTS/ASTR 206 – Mars: Early History15Subsequent spacecraft saw MUCH more interesting stuffFluvial channels – several billion years oldPYTS/ASTR 206 – Mars: Early History16Giant volcanoesLava flows up to ~1Myr oldPYTS/ASTR 206 – Mars: Early History17The giant Valles MarinerisPYTS/ASTR 206 – Mars: Early History18Polar ice capsPYTS/ASTR 206 – Mars: Early History19The best-explored planet! (apart from Earth)1960’s1970’s1990’s2000’sPYTS/ASTR 206 – Mars: Early History20A Mars Curse?Earth vs. MarsAlmost 50 years of exploration40 attempts to explore MarsMars in the lead… until now…Today’s Score 20 : 20PYTS/ASTR 206 – Mars: Early History21Phoenix EDL MoviePYTS/ASTR 206 – Mars: Early History22PYTS/ASTR 206 – Mars: Early History23PYTS/ASTR 206 – Mars: Early History24PYTS/ASTR 206 – Mars: Early History25GeographyIsidisUtopiaHemispheric dichotomyVolcanic provinces Impact basinsPolar Layered depositsPYTS/ASTR 206 – Mars: Early History26Three geologic periodsNoachian 4.1 - 3.93 GaHesperian 3.93 - 3.1 GaAmazonian 3.10 - 0.0 GaEarly Mars corresponds to the Noachian geologic periodStarts with the Hellas basin impactNimmo and Tanaka, 2005Surface history of Mars is available throughout the past 4.5 GyrSurfaces of Earth and Venus record only recent historySurfaces of Moon and Mercury record only ancient historyPYTS/ASTR 206 – Mars: Early History27Crystallization age of ALH840014.5 Ga – a very old rockIndicates stable crust already existedShock heating event at 3.9GaMars accretion was fastThe element Tungsten usually goes into the core in molten planetsExtra Tungsten produced by radioactive decay in the crust after core formsAmount of this extra Tungsten dates the core formationImplies martian core formation 13±2 Myr after earliest solar system solids formedKleine et al., 2002PYTS/ASTR 206 – Mars: Early History28Northern and southern hemispheres of Mars are very distinct:North Low elevationFew CratersYoungSmooth terrainThin CrustSouthHigh elevationHeavily crateredOldRough terrainThick crustCrustal DichotomyZuber et al., 2000PYTS/ASTR 206 – Mars: Early History29Many buried impact basinsNorthern lowlands look like the southern highlands after allForming the dichotomyOne Giant impact?Many not-so-giant impacts?Degree-1 convection?coreCrust melted hereExtra crust freezes herePYTS/ASTR 206 – Mars: Early History30Mars had a liquid metal coreCools off faster than Earth due to smaller sizeOnce the core froze
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