Curiosity finds metallic meteorite on Mars Credit NASA JPL Curiosity Team Course Announcements Thanksgiving Week planning No classes Wednesday 23 Nov Exam 2 grading update Close I ve been fighting a bad cold Extra Credit sessions still underway Update to Planetarium ECs 1 Regular Planetarium show 1 2 3 Any two Planetarium movies 1 1 Quiz 5 next Wednesday 9 Nov Hints on Today and Monday Assignments Reading Assignments Chapter 9 Sections 9 5 9 6 Read by Monday 7 Nov Parallel Lectures CC Astronomy Episode 15 Mars Watch before Monday 7 Nov Mastering Astronomy Chapter 9 Homework coming soon Quiz 5 Hints Sample questions and concepts What is the currently favored Moon formation hypothesis A Co formation Sister Hypothesis B Capture Hypothesis C Fission Daughter Hypothesis D Giant Impact Hypothesis E The Moon is an egg I could also ask you about why we favor the Giant Impact Hypothesis What are the major pieces of evidence that the formation idea must account for Quiz 5 Hints Sample questions and concepts Suppose we find a Moon of a planet and discover it has a 5 3 spin orbit resonance what does that mean A It orbits 5 times for every 3 rotations B It orbits 3 times for every 5 rotations C It has a synchronous orbit D It does not relate the the orbital period to rotational period Quiz 5 Hints Sample questions and concepts What formed the scarps that we see on Mercury A The giant impact that formed the Caloris Basin B Large scale lava flooding events C Mercury is shrinking and shriveling up like a raisin D Tidal stretching of Mercury from the Sun It is also a good idea to know what the major features of Mercury are especially if they are unique to Mercury Global Views of Venus Visible Light Yellow ish color super thick atmosphere super high surface temperature and bland at visible wavelengths Well that looks bland but yellow ish Dense atmosphere 90 atmospheres or atm Earth s atmosphere is 1 atm by definition 101 325 Pa 90 atm of pressure is similar to being a kilometer under the oceans Thickest atmosphere for all terr worlds 100 times more massive than Earth Atmosphere of Venus almost entirely composed of CO2 Gives surface temp of 740 K 870oF Crazy greenhouse effect Hot enough to melt lead True Color Image of Venus Credit NASA Mariner 10 R Nunes UV Global View of Venus Clouds Super thick atmosphere super high surface temperature and super fast rotation of clouds Top Ultraviolet UV image of Venus from Pioneer Reveals clouds colored white in the image similar to Earth s high altitude jet stream with speeds of 400 km hr 250 mph that s fast Super fast winds in high atmosphere a so called Super rotating atmosphere Encircles Venus in about 4 days much much faster than rotation period High altitude Radio Global View of Venus Surface Overall Global Features Two continent sized highlands covering 8 of the surface Ishtar Terra and Aphrodite Terra Lowlands that are fairly flat with rolling hills and modest higher elevations Young surface 300 600 million years old with few impact craters No plate tectonics but 167 volcanoes with base diameters 100 km That s really big for a volcano About 10x Earth shield volcanoes A brief aside Shield Volcanoes Discovered so far non Earth volcanoes are shield volcanoes Credit NASA Gal pagos Islands are Shield Volcanoes formed over hotspots not plate boundaries from viscous lava Low profile wide base Calderas form on the top of shield volcanoes Crater depressions not from impacts but from collapsed magma reservoir after it empties Shield Volcanoes Stratovolcanoes Surface of Venus Venus Mosaics Blue is not water Colors map elevation such that blue is low altitude and reds and whites are high altitude Thick clouds in atmosphere prevent us from seeing the surface in all but radio and IR wavelengths Pioneer South North Ishtar Terra Aphrodite Terra Magellan Surface of Venus Mercator Projections Poles grossly exaggerated Elevated continents Ishtar Terra in the southern high latitudes South polar area and Aphrodite Terra in equatorial regions cover about 8 of the surface Ishtar Terra approx same size as Australia Aphrodite Terra approx same size as Africa Note that there is no evidence for tectonics plates as can be seen with the Earth elevation map Lakshmi Planum Most prominent feature on Ishtar Terra Lakshmi Planum is a large plateau 1500 km across on Ishtar Terra Note the wrinkled mountain chains surrounding Lakshmi Planum Can also see impact crater Cleopatra 100 km on top of Venus s tallest mountain Maxell Montes 14 km Cleopatra crater on Maxwell Montes Ovda Regio Most prominent feature on Aphrodite Terra Ovda Regio is the dominate feature on Aphrodite Terra Ridges run in two different directions Not likely to form via plate tectonics Formation via compression favored with subsequent fracturing and buckling of the crust Dark radar patches are smooth old lava flows Evidence for at least recent if not current volcanism Lava Flows Indicative of a convective mantle Cracks in the crust like the one picture below have allowed lava to flow to the surface and flood the surrounding terrain Note With radar data dark smooth light rough This is an example of one type of volcanism on Venus Volcanism on Venus Venus s resurfacing is dominated by volcanism perhaps ongoing volcanism Venus s volcanoes are shield volcanoes 167 Volcanoes over 100 km in diameter Recall Earth s shield volcanoes are only about 10 km Right Sif Mons and Gula Mons Volcanism Pancake Domes Lava domes are scattered over entire surface of Venus Lava domes called pancake domes for obvious reasons 1 15 km in diameter Form when lava oozes to the surface forms a dome and after the lava retreats the domes collapse Usually located near coronae upcoming which are orders of magnitude larger Volcanism on Venus Pancake Domes Simulated view pancake domes yum Volcanism on Venus Coronae Largest volcanic features are coronae singular corona Coronae are unique to Venus Essentially super lava domes but much much much bigger Huge roughly circular regions 100s 1000s of km in diameter Likely produced by mantle convection creating a bulge in the crust and then collapsing forming the circular fractures Volcanism Still active Certainly recent volcanism but is it still occurring Plethora of volcanic features indicate that Venus has experienced significant volcanism Comparable in magnitude but less frequent than Earth Volcanic features evenly scattered about Venus Not like Earth where they cluster near plate boundaries More evidence
View Full Document
Unlocking...