Slide Number 1Slide Number 2Guiding QuestionsSlide Number 4Earth-based optical observations of Mercury are difficultSolar Transit Slide Number 7Mercury rotates slowly and has an unusual spin-orbiting couplingSlide Number 9Slide Number 10Slide Number 11Slide Number 12Images from Mariner 10 revealed Mercury’s heavily cratered surfaceSlide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Mercury has an iron core and a surprising magnetic fieldSlide Number 23Slide Number 24Slide Number 25The magnetosphere blocks the solar wind from reaching the surface of the planet Cloud-Covered VenusSlide Number 28Guiding QuestionsSlide Number 30The surface of Venus is hidden beneath a thick, highly reflective cloud coverIn 1962 the unmanned U.S. spacecraft Mariner 2 made the first close flyby of Venus Venus’s rotation is slow and “retrograde”Venus has a hot, dense atmosphere and corrosive cloud layersSlide Number 35Slide Number 36Volcanic eruptions are probably responsible for Venus’s cloudsSlide Number 38Slide Number 39The climate on Venus followed a different evolutionary path from that on EarthSlide Number 41The surface of Venus shows no evidence of plate tectonicsSlide Number 43Slide Number 44Slide Number 45Venusian SurfacesMarsWhat I’ll Talk AboutSlide Number 49The High HopesFrom Schiaparelli…To Percival LowellLowell’s Observations and ExplanationMore Historical BackgroundMariner 4, 6 and 7Mariner 4 PhotographsMariners 6 and 7A Time to Fail and SucceedMariner’s AtmosphereMariner 9 PhotographsA Prelude to VikingViking LiftoffViking InstrumentsArrival at MarsAnother Giant Leap for MankindThe Viking LookViking Orbiter PhotographThe Face on MarsThe Face on Mars - CaptionThe Changing FaceViking Lander PhotographReach Out and TouchFirst Results from Soil SampleA Mass DisappointmentLooking for LifePyrolytic Release ExperimentGas Exchange ExperimentLabeled Release ExperimentBiology Experiment ResultsExplaining Biology AwayLevin’s View 25 Years LaterViking’s View of AtmosphereFirst Mars Weather ReportViking Looks at ClimateViking Climate ConclusionsMore on Atmospheric FindingsA Little PressureMeridional Circulation [Say What?]A Little Mars GeologyMore Beautiful PicturesSummary of Mars Landing SitesPathfinder at Ares VallisSojournerMars Global SurveyorSlide Number 95Odyssey 2001Slide Number 97Slide Number 98Mars InteriorMars InteriorOlympus MonsSlide Number 102Valles MarinerisHellas BasinTerrain ComparisonThe Tharsis BulgeCanyon Widening EvidenceImpact CratersSlide Number 109Slide Number 110Slide Number 111Meteorite from MarsStatement from Daniel S. Goldin, NASA AdministratorGoldin Statement (August 6, 1996)Science Paper by McKay et al.Paper by Scott et al.Paper by Scott and BarberA Quick Review of MarsSimplified Conclusions re Mars1Terrestrial Planets – Begin With Mercury23Guiding Questions1. What makes Mercury such a difficult planet to see?2. What is unique about Mercury’s rotation?3. How do the surface features on Mercury differ from those on the Moon?4. Is Mercury’s internal structure more like that of the Earth or the Moon?488 days5Earth-based optical observations of Mercury are difficult• At its greatest eastern and western elongation, Mercury is never more than 28° from the Sun• It can be seen for only brief periods just after sunset or before sunrise6Solar TransitThere was a transit on November 8, 2006Transits occur about twelve times a century when the sun, Earth and Mercury are aligned7Earth-based Views of MercuryDifficulties observing Mercury from Earth led early astronomers to incorrectly decide that Mercury always kept the same face towards the sun in synchronous orbitNote phases like the moon8Mercury rotates slowly and has an unusual spin-orbiting coupling9Radio telescope observations from sites such as Arecibo gave evidence of a non-synchronous orbit1011• Mercury spins 1 ½ times on its axis for every complete orbit• Mercury spins three times during every two orbits12• Strong tidal effects, Mercury’s slightly elongated shape and its very eccentric orbit cause this strange 3-to-2 orbit• A “day” of solar light on Mercury would be 88 earth days13Images from Mariner 10 revealed Mercury’s heavily cratered surface• Most of our detailed information about Mercury’s surface is from the Mariner 10 flyby mission in 1974/1975.• Mariner only saw one side of the planet.• The MESSENGER mission spacecraft is now at Mercury.– It is adjusting its flight path for an ultimate orbit of Mercury– 3 flybys to date– Will achieve orbit in 201114MESSENGER SpacecraftImage from Flyby #3 - 200915• Heavily cratered surface• Less dense cratering than moon• Gently rolling plains• Scarps• No evidence of tectonics16Note how much more densely the craters occur on the Moon’s surface.17Scarps are cliffsThis one is more than a km highThey probably formed as the planet cooled and shrank1819• The Caloris Basin is evidence of a large impact20The seismic waves from the impact that caused the Caloris Basin caused this deformation on the opposite side of Mercury21This may be evidence of ice at Mercury’s North Pole.22Mercury has an iron core and a surprising magnetic field• Most iron-rich planet in the solar system with a core that is 75% of the diameter• The earth’s core is 55% of its diameter and the moon’s core is 20% of its diameter• Highest density for the planets• Weak magnetic field indicating part of the core is liquid• Magnetic field causes a magnetosphere similar to Earth’s but weaker23242526The magnetosphere blocks the solar wind from reaching the surface of the planet27Cloud-Covered Venus2829Guiding Questions1. What makes Venus such a brilliant “morning star” or “evening star”?2. What is strange about the rotation of Venus?3. In what ways does Venus’s atmosphere differ radically from our own?4. Why do astronomers suspect that there are active volcanoes on Venus?5. Why is there almost no water on Venus today? Why do astronomers think that water was once very common on Venus?6. Does Venus have the same kind of active surface geology as the Earth?30• At its greatest eastern and western elongations, Venus is about 47° from the Sun• It can be seen for several hours after sunset or before sunrise31The surface of Venus is hidden beneath a thick, highly reflective cloud cover• Venus is similar to the Earth in its size, mass, average density, and