phys183_lecture23.pdf - Prof. V. Kaspi Department of...

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PHYS 183Milky Way Inside andOutLecture 23Apr 6, 2021Prof. V. KaspiDepartment ofPhysicsMcGill SpaceInstituteThursday 10-11am or byappointment
Course Evaluations Open!Important exercise…please take seriously!Used for determining:Future teaching assignmentsTenure dossiersSalary increasesLooking for >50% response to drop 2nd lowest quiz!
Reading for this class7.3 “Mars: A Victim of Planetary Freeze-Drying”Ch 8: “Jovian Planet Systems”Covering only parts of this ChapterCh 9: “Asteroids, Comets and Dwarf Planets”Covering only parts of this Chapter
Today’s Class: Starting a Whirlwindtour of the Solar SystemMarsJovianplanetsComets
Mars“The Red Planet”RMars= 3390 km, MMars=6.4x1023kgRotates every 24 hrs, 39 minObliquity 25 degOrbital period 687 daysplanet has long captured ourimagination; best studiedhistorically because of claims of“canals”: since disprovedHas CO2ice polar caps that change inmorphology
Mars “canals”Giovanni Schiaparelli 1877: saw “canals:”straight lines on surfaceNo photographyPercival Lowell late 1800’s: claims Marsinhabited by intelligent lifeCanals seemed to change over yearsbuilt canals to get water from polar capsagriculture: seeing vegetation grow seasonally??Later realized optical illusionsMany point-like features in low-resolution telescopesjoined up to form ‘lines’Windsàdust stormsNot seen by modern telescopes or flybysToday we know there are no canals. Oh well.
Mars’ surface...Mars hasvolcanoes, though probablydormantmost are in northern hemisphere:Fewer craters in North than in Southlargest isOlympus Mons:24 km!one of several volcanoes in theTharsis riseregion, just north ofMars’ equatorVallesMarineris:giant canyon spanningboth hemispheres: 4000 km long!rift valley:crust brokeunlike Grand Canyon: water erosionno evidence for plate tectonicsValles MarinerisLarge volcanoesCloser View ofValles MarinerisOlympus Mons
Water was once on Mars!Alotof evidence water once flowed:dried up lakes and rivers, especiallyin older southern highlandsevidence for floodsevidence for water erosion of crater rimsdried upriverbedevidencefor flashflood

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Term
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Tags
Solar System, Planet, Comet

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