Mars InSight Lander Credit NASA JPL Caltech Artist s conception of InSight on Mars Credit NASA JPL Caltech Course Announcements Thanksgiving Week planning No classes Wednesday 23 Nov Extra Credit sessions still underway Quiz 5 Today Quiz 6 next Wednesday 16 Nov Exam 3 is Monday 21 Nov Exam materials released next week Final Exam Thursday 8 Dec 2 45 4 45 PM Astronomy Club Interest Meeting Friday 18 Nov 12 30 1 30 PM Nielsen 307 Assignments Reading Assignments Chapter 11 Sections 11 1 11 3 Read by Friday 11 Nov Parallel Lectures CC Astronomy Episode 16 JupiterCC Astronomy Episode 17 Jupiter s Moons Watch before Wed 16 Nov Mastering Astronomy Chapter 10 Homework short assignment Due Wed 16 Nov at 11 59 EST Appearing on Blackboard very soon Periods of Flowing Water Two types of channels implies two different wet eras Runoff channels suggest a wet period about 4 billion years ago end of Naochian Period when the Martian atmosphere was thick enough to support liquid water on the surface Outflow channels suggest a period about 3 7 3 billion years ago Hesperian Period characterized by large scale catastrophic periods of flooding Subsurface Ice Parts of Mars are more of a tundra than a cold desert NASA Phoenix Lander discovers water ice just below surface in northern arctic High latitudes have permafrost layer More equatorial areas may have permafrost as well but meters under surface Evidenced by fluidized ejecta Subsurface Ice Permafrost and fluidized ejecta Many Martian craters show fluid flow like features thought to be caused by fluidized ejecta Impact melts subsurface permafrost Spectral evidence reveals that subsurface areas mostly polar may be up to 50 water ice by volume Lower amounts 1 in the equatorial regions Mud like fluidized ejecta around Yuty Crater Credit NASA Current Flowing Water Recurring Slope Lineae RSLs Current Flowing Water It s salty Recurring Slope Lineae RSLs appear in Martian summer and are long dark streaks and disappear in colder winter temperatures Spectrally associated with hydrated salts Consistent with salty water flowing just below the surface Martian Polar Caps Two types The residual and the seasonal The Martian polar caps are predominantly dry ice CO2 ice but the residual North Polar Cap is water ice Must consider two parts of the Martian polar caps The seasonal cap grows and shrinks each year The residual cap remains permanently frozen Different for northern and southern polar caps At max size in southern mid winter the southern seasonal cap is 4 000 km across At max size in northern mid winder the northern seasonal cap is 3 000 km across Different because of Mars s eccentricity In southern winter Mars is further from the Sun nearer aphelion Colder winter larger growth for southern seasonal cap Martian Polar Caps Two types The residual and the seasonal Seasonal Cap Residual Cap Martian Polar Caps Seasonal Caps The seasonal caps are composed almost entirely carbon dioxide with temperatures lower than the 150 120oC required for CO2 to condense out of the atmosphere HINT GREAT Exam material just sayin Growth and retreat of seasonal caps responsible changes the atmospheric surface pressure by nearly 30 That s right About 30 of the atmosphere freezes out of the atmosphere when the the sum of the seasonal caps is largest compared to when smallest Maximum thickness thought to be 1 m not very thick but that translates to a lot of CO2 gas when it sublimates Martian Polar Caps Residual Caps roughly scaled North Residual Cap Water ice South Residual Cap CO2 ice Martian Polar Caps Residual Caps The residual caps are brighter and smaller than seasonal caps and even more marked by a northsouth asymmetry Southern 350 km across and almost entirely CO2 Northern 1000 km across and almost entirely water H2O ice Again great exam material here Larger because in southern summer Mars is significantly closer to the Sun reducing the size of cap i e Northern summer the best time to sublimate a residual cap occurs when Mars is nearer aphelion making it a more mild summer Where did the water go All this evidence points toward an ancient period when Mars was much wetter than it is now Where is the water now 1 Into the subsurface where it remains frozen most of the water 2 Lost to space via the photodisassociation of H2O into H2 and O2 Having so little mass the H2 can easily escape the low Martian gravity and escape to space and the oxygen reacted with surface 3 Some locked in permanent North Polar Cap If all the permafrost water on Mars were to become liquid there would be enough water to cover the surface to roughly a depth of 10 meters Martian Atmosphere 1 150th of Earth s Viking 1 Image NASA Martian Atmosphere 1 150th of Earth s Surface Pressure Varies from 4 0 8 7 mbar depending on season mbar millibar Atmospheric Composition 95 3 CO2 2 7 N2 1 6 Argon 0 13 O2 0 07 CO 0 03 water vapor Troposphere appears during the daytime and disappears at night i e the atmosphere incapable of producing convection or weather at night Martian Atmosphere Weather Dust storms Mars periodically experiences large scale dust storms Global dust storms on average once every 5 5 years 1 3 continent sized storms per Martian year Good potential exam question What planet periodically experiences global dust storms Change in opacity over 30 sols during a dust storm as viewed by Opportunity Martian Atmosphere Weather Dust devils Dust devils are common in the summertime and much larger than on Earth several km tall and 10s 100s m in diameter can be much larger than Earth tornadoes Serendipitous cleaning events for rovers Martian Atmosphere Weather Dust devils Before and After photos of Spirit rover after a dust devil cleaning event 2007 2008 Atmospheric Stripping via Solar Wind Solar wind erosion of Mars s atmosphere Recent result 2015 from MAVEN Amount of atmosphere stripped significantly increases during Solar storms increased Solar Wind Charged solar wind particles carry off ions of Oxygen and Carbon An artist s conception of a Solar storm stripping away Mars s atmosphere Atmospheric Stripping via Solar Wind Solar wind erosion of Mars s atmosphere Majority stripped rapidly after loss of global magnetic field Current non solar storm stripping rate 100 grams s Over the course of the past 4 Billion years or so this process has eroded away the Martian atmosphere Back calculation reveals that ancient Mars was much warmer with a thick atmosphere capable of retaining liquid water on its surface An artist s
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