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3 - 4 Venus

3 - 4 Venus. Eros punished by Venus. Transit of Venus. The planet Venus appears to cross in front of the Sun as seen from Earth . Rare celestial event The last "Venus transit" occurred in 1882. You will have another chance in 2012 (June 6). After that, you have to wait until 2117.

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3 - 4 Venus

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  1. 3 - 4 Venus Eros punished by Venus

  2. Transit of Venus The planet Venus appears to cross in front of the Sun as seen from Earth Rare celestial event The last "Venus transit" occurred in 1882 You will have another chance in 2012 (June 6) After that, you have to wait until 2117

  3. Astronomical unit (AU) Kepler’s third law: if you measure the orbital period of a planet (T), you can calculate its distance to the Sun, R, in AU R 1 AU Earth

  4. How large is an astronomical unit?

  5. 1874: Many countries sent expeditions to remote corners of the world to time 1882 Venus transit 8 of the expeditions were equipped with state of the art photographic plates Animation Simon Newcomb, in charge of the U.S. Venus Transit Commission, published his best estimate of the AU in 1891: ~ 149,000,000 km

  6. Why doesn’t the transit happen all the time?

  7. Orbit of Venus as seen from Earth

  8. 2004: conjunction at a node

  9. Evening or morning star

  10. Mass = 82% Earth’s mass Density ~ Earth’s density “Twin sisters”

  11. Retrograde rotation 243 Earth days to spin on its axis (rotation period) 225 Earth days to orbit the Sun (orbital period) A Venusian day is longer than a Venusian year

  12. Spacecraft exploration More spacecrafts sent than to any other planet Venera 15

  13. 1962 - Mariner 2 flyby as close as 35 000 km • 1967: Venera 4 , Mariner 5 • 1969: Venera 5 and 6 • 1970 - Venera 7: first soft landing • 1972: Venera 8 • 1975 - Venera 9: images of the ground • 1978 - Pioneer Orbiter (1 and 2) : radar map. Venera 11 and 12 • 1981: Venera 13 and 14 • 1983: Venera 15 and 16 • 1984: Vega 1 and 2 • 1990-94 - Magellan probe: radar map at a resolution of 100m (~ footballfield)

  14. Failures • 1963: Cosmos 21: stuck in orbit around the Earth • 1964: Cosmos 21: stuck in orbit around the Earth • 1964: Zond 1: lost radio contact with the Earth • 1965: Venera 2: came close to Venus but radio contact was lost • 1965: Venera 3: crashed on Venus, radio contact was lost before • Venera 5: radio contact was lost • Venera 6: radio contact was lost • Venera 9: probe landed and took one picture • 1975: Venera 10: probe landed and took one picture

  15. Appearance Dense clouds that reflect 70% of the sunlight: the surface is not visible UV

  16. Thick atmosphere => probing through the clouds with radars Blue = low Red = high Bright = rough terrain Dark = smooth terrain

  17. May 89: Magellan launch First detailed look at the surface of our sister planet Sent each 100 minutes enough data to fill a 60 volume encyclopedia

  18. Nothing obscures or erases the geological features No ice or water and winds are slow + High geological activity = Volcanologist’s dream planet

  19. 75 % of the surface consists of low land lava plains

  20. Two continents of mountainous terrain: • Aphrodite (size of Africa) • Ishtar (size of Australia)

  21. Impact craters Diameter = 275 km Mead: largest impact crater

  22. Multiple craters What caused such craters? 50 km 3 projectiles, ~ 5km large each, crashed at once Lavina region

  23. Gertrude Stein triple impact Why don’t we see this feature on the Moon or Mercury? Caused by the breaking apart of an asteroid during its passage through the thick atmosphere

  24. Crater statistics show very few craters less than 10 km in diameter . Why? Projectiles smaller than 1 km were stopped by the atmosphere (heated up and transformed into gas) Crater count : 15 % as many craters in venusian plains as on lunar maria. How old is the surface of Venus? 3.3 billion x 15% = 500 million years old Conclusion ? Venus is a planet with persistent geological activity It experienced planet wide volcanic activity 500 million years ago

  25. Impact craters are young

  26. volcanoes Widespread volcanism Many different types of features Double crater

  27. Thousands of volcanoes dot the surface Most seem similar to terrestrial volcanoes, others have unusual shapes “Pancake domes” Circular domes are the result of eruptions of highly sludgy lava 25 km

  28. Pancakes, side view 2 km

  29. Magma can collect to produce bulges in the crust: large circular or oval features called coronae 200 km Fotla Corona

  30. No evidence of subduction zone => no plates HEAT

  31. MAAT MONS. Highest volcano on Venus, Maat has an elevation of about 8 km. Might be active.

  32. Tectonic activity OZZA MONS, across a broad array of cracks and linear strikes

  33. Convection currents in the mantle push and stretch the crust itself = “tectonic forces” They break lava surface to create patterns of ridges and cracks.

  34. Can even produce rift valleys

  35. Maxwell Mountains, rising some 11 km above the surrounding plains: product of compression of the crust tiny animation Highest mountain range in the solar system

  36. atmosphere 460oC

  37. Greenhouses Greenhouses work by trapping heat from the sun. The glass panels let in sunlight but keep heat from escaping The greenhouse heats up (like the inside of a car parked in sunlight)

  38. 96% CO2 (Earth: 0.03%)

  39. Venera 13. Everything is orange because the thick atmosphere absorbs blue light. The surface is lit by diffuse light (same as on Earth under a heavy overcast)

  40. Surface pressure would crush you on the ground (90 atm) An appealing holiday resort Temperature hot enough to melt lead and zinc 96% carbon dioxyde Absence of liquid water Venus' slow-moving ground winds are more powerful than Earthly hurricanes

  41. An artist view of an acid canyon 30 - 60 km above the surface: a thick layer of sulfuric acid clouds

  42. An artist view of a sulfur sky The sulfur dioxide produced by volcanoes is stable (one Earth it is washed out by rainfall)

  43. Twin sisters? Hell Heaven

  44. Venus enigma Presence of recent lava flows => active volcanoes => hot mantle and core Sulfur content of air => hot mantle and core Hot liquid rotating core => magnetic field However no magnetic field has been detected. Why?

  45. Answer The rotation is too slow to create an intense (and detectable) magnetic field. Remember: one Venusian day = 243 Earth days

  46. News about Venus

  47. Venus Express (ESA) LAUNCH DATE:26-Oct-2005 04:43 UT   MISSION : 500 days in Venus orbit October 2004

  48. Testing the deployment of the solar arrays. Dec 2004

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