11/6/2020

Today’s Class: The Planet Venus Last Class

• Further reading on Venus & Climate • Mercury Change for next class – –Interiors of Terrestrial Planets. Section 10.5 in Cosmic • Heating Perspective. • Homework #5 due on • Cooling Monday. –What geological processes shaped • Back to on-line Mercury? learning starting Nov. 16. –NASA’s Messenger mission to Mercury.

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Today’s Class Overview of Venus

• Overview of Venus. • Measuring distance to Venus. • What geological processes shaped Venus? – Cratering – Volcanism – Tectonics • Spacecraft Observations of Venus • Nearly identical in size to Earth (radius is 95% of Earth); mass = – Venera 82% of Earth; surface hidden by clouds • Hellish conditions due to an extreme Greenhouse Effect! – Magellan • Even hotter than Mercury: 470C (880F), day and night Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration 3 4

Transit of Venus Measuring Distance to Venus

• Apparent • Measure apparent position of position of Venus on Venus on Sun Sun from two during transit locations on Earth depends on • Use trigonometry to distances in determine Venus's solar system distance from the and your distance between the position on two locations on Earth Transit of Venus: June 6, 2012 Earth.

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What geological processes have Terrestrial Planet Interiors shaped Venus?

• Interiors of Venus and Earth appear to be very similar. • But, Venus’ rotation period is 243 Earth days! • Does Venus have a planet-wide magnetic field?

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Radar Mapping Cratering on Venus

• Venus has

Insert TCP7e impact craters, figure 9.35 but fewer than the Moon, Mercury, or Mars.

• Its thick atmosphere forces us to explore Venus's surface through radar mapping. Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration 9 10

Class Exercise: Why do you think Venus has Why do you think Venus has few impact few impact craters relative to Mars? craters relative to Mars?

a) Venus is so close to the Sun that it was a) Venus is so close to the Sun that it was never bombarded by asteroids or comets. never bombarded by asteroids or comets. b) It’s thick atmosphere stopped most of the b) It’s thick atmosphere stopped most of the impactors. impactors. c) Other geological processes have wiped out c) Other geological processes have wiped out craters. craters. d) Ancient dinosaurs on Venus destroyed d) Ancient dinosaurs on Venus destroyed evidence of previous impacts. evidence of previous impacts.

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Volcanoes on Venus Stratovolcano outside of Puebla, Mexico

• It has many volcanoes, including both shield volcanoes and stratovolcanoes.

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Tectonics on Venus Does Venus have plate tectonics?

• The planet's • Venus does not appear to have plate tectonics, but entire surface seems to have fractured and been "repaved" 750 million years ago. contorted • Weaker convection? surface indicates • Thicker or more rigid lithosphere? tectonic stresses.

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Erosion on Venus Spacecraft Observations of Venus USSR Venera Missions: • Photos of rocks • Total of 16 launches from 1961 – 1983. taken by • Many launch failures. landers show • First and only images of the little erosion. surface of Venus!

=> Too hot for rain or ice and slow rotation means weak surface winds.

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Spacecraft Observations of Venus

U.S Magellan Mission: • 1989-1994 • Collected radar images of 98% of the planet. • Studied role of impacts, volcanism, & tectonics. • Found lava channels 6000 km long. • No evidence of wind erosion in contrast to Mars

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