Curiosity finds metallic meteorite on MarsCourse AnnouncementsAssignmentsQuiz 5 HintsQuiz 5 HintsQuiz 5 HintsGlobal Views of Venus – Visible LightUV Global View of Venus - CloudsRadio Global View of Venus - SurfaceA brief aside: Shield VolcanoesSurface of VenusSurface of VenusSlide 13Lakshmi PlanumOvda RegioLava FlowsVolcanism on VenusVolcanism – Pancake DomesVolcanism on Venus: Pancake DomesVolcanism on Venus: CoronaeVolcanism – Still active?Volcanism – Still active?Volcanism – New Venus Express DataImpact CratersData from Soviet LandersSurface of Venus - AgeAtmosphere of VenusAtmosphere of VenusAtmosphere of VenusAtmospheric CompositionGreenhouse Effect on VenusGreenhouse Effect on VenusThe Runaway Greenhouse EffectThe Runaway Greenhouse EffectThe Runaway Greenhouse EffectThe Runaway Greenhouse EffectThe Runaway Greenhouse EffectDefining a “Habitable Zone”Habitable Zone (“Goldilocks” Zone)Habitable Zone DependenciesVenus’s Magnetic Field and Internal StructureWhy no plate tectonics?Curiosity finds metallic meteorite on MarsCredit : NASA/JPL/Curiosity TeamCourse Announcements•Thanksgiving Week planningNo classes Wednesday, 23 Nov.•Exam 2 grading update–Close… I’ve been fighting a bad cold•Extra Credit sessions still underwayUpdate to Planetarium ECs1. Regular Planetarium show (+1)2&3. Any two Planetarium movies (+1 +1)•Quiz 5 next Wednesday, 9 Nov.–Hints on Today and MondayAssignmentsReading Assignments•Chapter 9: Sections 9.5 – 9.6[Read by Monday, 7 Nov.]•Parallel LecturesCC Astronomy Episode 15: Mars[Watch before Monday, 7 Nov.]Mastering Astronomy•Chapter 9 Homework coming soonQuiz 5 HintsWhat is the currently favored Moon formation hypothesis?A) Co-formation (Sister) HypothesisB) Capture HypothesisC) Fission (Daughter) HypothesisD) Giant Impact HypothesisE) 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?Sample questions and conceptsQuiz 5 HintsSuppose 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 rotationsB) It orbits 3 times for every 5 rotationsC) It has a synchronous orbitD) It does not relate the the orbital period to rotational period.Sample questions and conceptsQuiz 5 HintsWhat formed the scarps that we see on Mercury?A. The giant impact that formed the Caloris BasinB. Large-scale lava flooding eventsC. Mercury is shrinking and shriveling up like a raisinD. 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.Sample questions and conceptsGlobal Views of Venus – Visible LightWell, 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 leadYellow-ish color; super thick atmosphere; super high surface temperature; and bland at visible wavelengths“True” Color Image of VenusCredit: NASA/Mariner 10/R. NunesUV Global View of Venus - CloudsTop: 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 altitudeSuper thick atmosphere; super high surface temperature; and super-fast rotation of clouds!Radio Global View of Venus - Surface•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 volcanoesOverall Global FeaturesA brief aside: Shield Volcanoes•Discovered so far, non-Earth volcanoes 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 emptiesShield VolcanoesStratovolcanoesGalápagos Islands are Shield Volcanoes Credit: NASASurface of VenusThick clouds in atmosphere prevent us from seeing the surface in all but radio and IR wavelengthsVenus MosaicsPioneer MagellanIshtar Terra Aphrodite Terra“North”“South”Blue is not water! Colors map elevation, such that blue is low altitude and reds and whites are high altitudeSurface of VenusMercator Projections – Poles grossly exaggeratedElevated “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 AustraliaAphrodite Terra approx. same size as AfricaNote that there is no evidence for tectonics plates as can be seen with the Earth elevation map.Lakshmi PlanumMost prominent feature on Ishtar TerraLakshmi 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 onMaxwell MontesOvda RegioMost prominent feature on Aphrodite TerraOvda 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 crustDark radar patches are smooth, old lava flowsEvidence for at least recent (if not current) volcanismLava Flows•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 VenusIndicative of a convective mantleVolcanism on Venus•Venus’s volcanoes are shield volcanoes•167
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