Venus - Overview. Exploration of Venus. Admin. 9/26/17. Second planet from Sun Earth s sister planet

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1 Admin. 9/26/17 1. Class website 2. Optional Discussion sections: Tue. ~11.30am (period 5), Bryant 3; Thur. ~12.35pm (end of period 5 and period 6), start in Pugh 170, then Bryant 3 3. Office hr: Tuesday pm; Wed pm, Bryant 302 (but me if coming on Wed.). 4. Homework 4: is due Mon. Oct 2nd 11.59pm via Canvas e-learning under Quizzes 5. Reading this week: Chapters 0, 1, , 4.1, 5, 6, 7, 8, 4.2, Midterm 1: was on Thur. Sept. 21st: results via Canvas e-learning soon. 7. Observing project deadline: Thursday Oct. 26th 2017, however, you are strongly advised to complete observing by Fri. Oct. 6th. 8. Astro-news, jokes, tunes, images: ast1002_tan-l@lists.ufl.edu 9. Printed class notes? Name tags? - Overview Second planet from Sun s sister planet similar sizes, masses, densities, cratering & chemical compositions Property Radius 6052 km 6378 km Mass 4.7 x Kg 6.0 x kg Density 5240 kg/m kg/m 3 Escape Speed 10.4 km/sec 11.2 km/sec Atmosphere Carbon dioxide, Nitrogen Nitrogen, Oxygen Key Concepts: Lecture 14 : structure, surface, magnetic field Atmosphere (runaway greenhouse) Use of radar: transparency of atmospheres in radio; Doppler effect Comparison of Terrestrial Planets Exploration of Telescopic observation of Only see cloud layers reflect 76% of incoming sunlight Visited by ~ 20 spacecraft Mariner 2 - first to visit in 1962 Venera 7 - Soviet Space Craft - first to land on another planet Venera 9 - first photographs of surface Magellan - detailed maps of surface from radar

2 Orbit and Rotation Orbit of around Sun most circular orbit of all planets 225 days for 1 complete orbit Rotation of Retrograde - in opposite direction of most other planets and most satellites in solar system Very slow: 243 days for 1 full rotation (siderial day); 117 days for solar day. Magnetic Field Very, very weak magnetic field - Why? rotates much more slowly (243 times) than internal dynamo weaker weaker magnetic field - 10,000 times weaker than! Interaction with solar wind differs from solar wind runs right into upper atmosphere of carries off some of the atmosphere Structure of Surface of Interior structure similar to similar mass, size & density Metallic somewhat lower density than somewhat smaller than Large rocky mantle y crust Varied Terrain mountains high plateaus canyons ridges craters Overall relatively flat compared to Only 10% of surface above 10 km

3 Radar to map surface Atmospheres are quite transparent in the radio wave band. and measure rotation rates Uses Doppler effect: waves are compressed if emitting object is moving towards us; expanded if moving away from us. Surface of Few craters Several upland plateaus, resembling continents Low-land lava plains Some volcanoes, maybe active, as revealed by variable gas emissions in atmosphere Radar map: Surface of - Volcanoes and Lava Domes Volcanoes occur in complex groups Lava Domes Shield volcanoes relatively flat often having a collapsed central volcanic crater at summit

4 Surface of - Impact Craters Temperature & Pressure Temperature increases as you get closer to the surface Relatively few impact craters young surface overall No small craters small meteoroids burn up in dense atmosphere Craters come in bunches large meteoroids that reach surface break up in atmosphere Atmosphere of Constituents: 96% carbon dioxide 3.5% nitrogen water, sulfuric acid clouds, hydrochloric acid Variability may indicate volcanic eruptions Fast winds in upper atmosphere, almost no wind at surface surface temperature ~800 K Pressure increases as you get closer to the surface 90 times greater than s surface pressure! Greenhouse Effect on ~76% of sunlight reflected by clouds & never reaches surface Yet surface temperature extremely high! Surface temperature high due to strong greenhouse effect No oceans or life to remove CO2

5 Questions about Evolution of Terrestrial Planets: interiors Why is its rotation retrograde? Perhaps due to giant impact. Why did atmosphere evolve so differently than the s? Probably because conditions never arose for large amounts of liquid water oceans (too hot initially, or not enough supplied by comets). Evolutionary Stage of Terrestrial Planets Planet accretes from planetesimals Solid crust forms. Heavy infall of planetesimals -> cratering Major cratering ends. Mare-type basins flood with lava. Surface tectonically active. Volcanoes, plate motions or other mantle motions. Mantle solidifies. Tectonic activity ends on surface. Interior cold. All tectonic activity stops. Mars Mercury Moon Small planets cool fastest and go through this planetary evolution faster Summary: Terrestrial Planets Evolution of Terrestrial Planets: atmospheres Mercury Mars Mercury All terrestrial planets are differentiated Larger planets take longer to cool and still have active mantles (plate tectonics on, active volcanoes on & ) and liquid s Mars Tsurface ~ 623K (day) ~ 100K (night) Volcanic activity creates secondary atmosphere Gravity holds atmosphere. Light atoms escape most easily. Higher temperatures allow heavier atoms to escape Water and life remove CO 2 and life creates O 2 Tsurface ~ 750K Tsurface ~ 300K Tsurface ~ 218K