PYTS/ASTR 206 – Mars: Early History1z AnnouncementsUPi kSh TAUse Priyanka Sharma as TA [email protected] Office hours: Tuesday 10.30am-12.30pmRoom 316, Kuiper BuildingPYTS/ASTR 206 – Mars: Early History2Mars – Early HistoryPTYS/ASTR 206 – The Golden Age of Planetary ExplorationShane Byrne – [email protected]/ASTR 206 – Mars: Early History3In this lecture…In this lecture…IntroductionzIntroduction Comparisons to Earth Seasons on Mars Early ideasz Spacecraft exploration Not Earth-like after all Familiar landformsz Early Martian History Crustal dichotomy Large impacts and volcanic activitygp y Magnetic fields Valley networksPYTS/ASTR 206 – Mars: Early History4OfthlttilltIntroductionIntroductionzOne of the larger terrestrial planets Intermediate between Mercury/Moon and Earth/VenusPYTS/ASTR 206 – Mars: Early History5z Comparison to the Earth A mini-Earth?MarsSize 53% of the EarthMass 11% of the EarthDensity3934 kg m3RoughlyThe SameDensity3934 kg m-3(Earth/Venus ~ 5500 kg m-3)Solar Distance 1.52 AUInternalStructureYear 687 days, 1.9 Earth yearsObliquity25°Days andSeasonsiilqy(Earth = 23½°)Rotation period 24hrs 37 minutes(Earth = 1 day)similarto theEarthSurface Earth-like rocks and landformsSome parts heavily crateredSimilarSurfacePYTS/ASTR 206 – Mars: Early History6z Comparison with the Earth IIHhlditidMi?How much solar radiation does Mars receive? Remember:Solar power = 1367 W m-2/ R2 Mars is 1.52 AU from the Sun: R=1.52SSolar power = 1367 W m-2/1522So: Solar power at Mars is 592 W m-2(about half that of Earth)Solar power = 1367 W m-2/ 1.522z Mars is a much colder place… Harder for liquid water (& life) to exist Not always the case though… Early Mars was quite differentPYTS/ASTR 206 – Mars: Early History7z Differences from the EarthMarsAtmosphere Mostly CO2(Earth = Mostly nitrogen)Pressure 0.006 bars(Earth = 1 bar)Surface Temp. 200K(Earth = 300 K)VeryDifferentAtmosphereClouds Water ice and dust(Earth = water vapor)Magnetic field None(Earth has a strong field)Seasonal ice Carbon dioxide(Earth has water frost)PYTS/ASTR 206 – Mars: Early History8zEarly telescopic observations showedSeasons on MarsSeasons on MarszEarly telescopic observations showed Seasonally advancing and retreating ice capsMars obliquity is similar to the EarthMars obliquity is similar to the Earth 25° vs. 23½°PYTS/ASTR 206 – Mars: Early History9z Mars has similar seasons to EarthM h i il d /iht lzMars has similar day/night cyclesz Mars has seasonal ice that comes and goesz Mars has changing patterns on the surface Seasonal vegetation growth? Uf t tl tUnfortunately not…PYTS/ASTR 206 – Mars: Early History10z Early telescopic maps were pretty crude… Giovanni Schiaparelli made maps with ‘channels’ (Canali in Italian)PYTS/ASTR 206 – Mars: Early History11z Percival Lowell made many telescopic observations of MarsTranslated Canali as CanalsTranslated Canali as Canals Popularized 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 equatorCanals were transporting water from the polar caps to the equatorPYTS/ASTR 206 – Mars: Early History12z Mariner 4 was the first spacecraft to visit Mars… July 1965py Flyby mission -PYTS/ASTR 206 – Mars: Early History13z What did Mariner 4 see? First planetary (non-lunar) mission to carry a camera Craters Not good for lifeAthithA very thin atmosphere Not good for lifeNo protective magnetic fieldNo protective magnetic field Not good for life Looked pretty much like the Moon Disappointing… Dry, cold, dead….PYTS/ASTR 206 – Mars: Early History14z The best-explored planet! (apart from Earth)1960’s1970’s1990’s2000’sPYTS/ASTR 206 – Mars: Early History15z Subsequent spacecraft saw MUCH more interesting stuffFluvial channels–several billion years oldFluvial channels several billion years oldPYTS/ASTR 206 – Mars: Early History16z Giant volcanoesLava flows up to ~1Myr oldLava flows up to ~1Myr oldPYTS/ASTR 206 – Mars: Early History17z The giant Valles MarinerisPYTS/ASTR 206 – Mars: Early History18z Polar ice capsPYTS/ASTR 206 – Mars: Early History19z The best-explored planet! (apart from Earth)1960’s1970’s1990’s2000’sPYTS/ASTR 206 – Mars: Early History20z A Mars Curse?zEarthvsMarszEarth vs. Mars Almost 50 years of exploration 40 attempts to explore Mars Mars in the lead… until now…Today’sScoreToday s Score20 : 20PYTS/ASTR 206 – Mars: Early History21Phoenix EDL MoviePhoenix EDL MoviePYTS/ASTR 206 – Mars: Early History22PYTS/ASTR 206 – Mars: Early History23PYTS/ASTR 206 – Mars: Early History24PYTS/ASTR 206 – Mars: Early History25Geographyz Hemispheric dichotomyz Volcanic provinces z Impact basinsIsidisUtopiabasinsz Polar Layered depositsPYTS/ASTR 206 – Mars: Early History26z Three geologic periodsNoachian41-393GaSurface history of Mars is available throughout the past 4 5Noachian4.1 -3.93 Ga Hesperian 3.93 - 3.1 Ga Amazonian 3.10 - 0.0 Gaavailable throughout the past 4.5 GyrSurfaces of Earth and Venus record z Early Mars corresponds to the Noachian geologic period Starts with the Hellas basin impactonly recent historySurfaces of Moon and Mercury record only ancient historyyyNimmo and Tanaka, 2005PYTS/ASTR 206 – Mars: Early History27z Crystallization age of ALH84001 4.5 Ga – a very old rock Indicates stable crust already itdexisted Shock heating event at 3.9Gaz Mars accretion was fast The element Tungsten usually goes into the core in molten planetsplanets Extra Tungsten produced by radioactive decay in the crust after core forms Amount of this extra Tungsten dates the core formation Implies martian core formation 13±2 M r after earliest solar13±2 Myr after earliest solar system solids formedKleine et al., 2002PYTS/ASTR 206 – Mars: Early History28zNorthern and southernCrustal DichotomyzNorthern and southern hemispheres of Mars are very distinct: North Low elevationFew CratersFew Craters Young Smooth terrain Thin CrustZuber et al., 2000 South High elevation Heavily cratered Old Rough terrain Thick crustPYTS/ASTR 206 – Mars: Early History29z Many buried impact basinsyp Northern lowlands look like the southern highlands after
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