Venus

1. Venus

2. VenusEarth’s “sister planet” 0.72 AU from Sun ~2x farther from Sun than Mercury so ~4x less sunlight ~1.4x closer than Earth so sunlight is (1.4)2 times =~2x more intense Venus approaches closer to Earth than any other planet so we should know a lot about it. However, its surface is invisible underneath a thick atmosphere. “true” color image

3. Venusglobal properties albedo = 0.65 mass = 0.815 of Earth’s diameter = 0.95 of Earth's density = 5.3 gm/cm3 surface gravity = 0.91 Earth’s axial tilt = 177.3 deg. ORBIT: 0.72 AU = semi. axis 0.0068 = eccentricity 3.4 deg = inclination 224.7 day = period “false color” image in UV

4. RADAR: “Radio Detection and Ranging” 1962:Carpenter & Goldstein (US) used radar "echoes“ to study Venus’ surface Arecibo Observatory in Puerto Rico "double" inverse square problem

5. Mapping the Surface via RadarVenus is the most thoroughly mapped of any planet movie 98% of the surface has been mapped to 100 meters resolution Over 80% of Venus’ surface lies within 1 km of its mean radius

6. Radar Mapping

7. Radar Mapping

8. 0 Radar Map of Venus’ Surface Surface features shown in artificial colors. Scattered impact craters Volcanic regions Smooth lava flows

9. 0 Lava Flows Young, uneven lava flows (shown: Lava flow near Flagstaff, AZ) show up as bright regions on radar maps.

10. 0 Surface Features on Venus Highland regions: Smooth lowlands Maxwell Montes are ~ 50 % higher than Mt. Everest!

11. 0 Craters on Venus Nearly 1000 impact craters on Venus’ surface: → Surface not very old. No water on the surface; thick, dense atmosphere → No erosion Craters appear sharp and fresh

12. 0 Shield Volcanoes Found above hot spots: Fluid magma chamber, from which lava erupts repeatedly through surface layers above. All volcanoes on Venus are shield volcanoes

13. 0 Volcanism on Venus Sapas Mons (radar image) ~ 400 km (250 miles) 2 lava-filled calderas Lava flows

14. 0 Volcanic Features on Venus Aine Corona Coronae: Circular bulges formed by volcanic activity Baltis Vallis: 6800 km long lava flow channel (longest in the solar system!) Lava flows Pancake Domes: Some lava flows collapsed after molten lava drained away Associated with volcanic activity forming coronae

15. 0 LakshmiPlanum and Maxwell Mountains Radar image Wrinkled mountain formations indicate compression and wrinkling, though there is no evidence of plate tectonics on Venus.

16. Surface “Flights”computer generated images from radar data Alpha Regio Vertical scale is exaggerated for visibility

17. Impact Craters About 1000 craters are located randomly around Venus. Venus’s atmosphere is a shield very few craters <35 km diameter Craters show little modification by tectonism or volcanism. Few craters suggests the surface is relatively young. ~30 km diameter Largest crater is Mead ~280 km diameter with a double-ring.

18. Effects of a Hot Surface Impact crater Addams, 90 km diameter. The surface is so hot that impacts more easily melt the surface than on other planets. Outflow of lava extends 600 km away.

19. Volcanoes & Lava Flowsover 10,000 small shield volcanoes Gula Mons 3 km tall volcano Maat Mons 8 km tall volcano with lava flows extending hundreds of km

20. 1962-1994: Spacecraft to Venus Unmanned Spacecraft US: Mariner 2, 5, 10 flybys Pioneer Venus orbiter & probes (1st radar from space) Magellan (high resolution radar)Galileo (flybys enroute to Jupiter) Soviet: Venera 4-16 (#7,8; 9,10; 13,14 landed)VEGA 1, 2 (landers & balloons) Surface map from 10 years of radar data

21. Lava Channels1-2 km wide and at least 100’s of km long Baltis Vallis Longest channel in solar system: 6800 km long and 1.8 km wide Lo Chen Vallis 12 km diameter crater

22. How Does Venus Release Its Heat?Volcanic plumes instead of plate tectonics? Arachnoids Circular features with concentric rings & fractures with diameters 50-230 km Coronae Circular troughs around volcanic plateaus Could the troughs be subduction zones? Artemis Corona 2000 km diameter 6 km from rim to trough 528 km across

23. The Surface as Imaged by Venera 14Composition: volcanic basalt These surface probes typically survived about one hour

24. 0 The Surface of Venus Early radar images already revealed mountains, plains, craters. More details from orbiting and landing spacecraft: Venera 13 photograph of surface of Venus: Colors modified by clouds in Venus’ atmosphere After correction for atmospheric color effect:

25. Atmosphere96.5% CO2, 3.5% N2 -- no O2 or H2Oalso acids: hydrochloric, hydrofluoric & sulfuric Dark areas are locations of the sulfuric acid clouds. Bright areas are gaps between clouds. Clouds near equator are fluffy but those at higher latitudes are stretched by high winds. H2SO4 (sulfuric acid) clouds may come from SO2 outgassing from active volcanoes Nighttime side of Venus in false-color image from a near-infrared camera (2.3mm) on the Galileo spacecraft

26. 0 The Atmosphere of Venus 4 thick cloud layers (→ surface invisible to us from Earth). UV image Very stable circulation patterns with high-speed winds (up to 240 km/h) Extremely inhospitable: 96 % carbon dioxide (CO2) Very efficient “greenhouse”! 3.5 % nitrogen (N2) Rest: water (H2O), hydrochloric acid (HCl), hydrofluoric acid (HF) Extremely high surface temperature up to 745 K (= 880 oF)

27. “Greenhouse Effect”Venus is the hottest planet and has the densest atmosphere 1950's: radio wave emission surface temperature: 750 K = 900 F Venus’ thick CO2 atmosphere keeps the surface hot. Surface pressure is 100x Earth’s How many pounds per square-inch? [same as ~3000 feet under water] Sulfuric acid clouds “runaway greenhouse effect”

28. No Magnetic Field 25,000 x weaker than Earth’s Too slow a rotator to generate an internal dynamo Perhaps Venus’ lack of crustal plates inhibits internal convection currents of molten rocks.