ES2232F_Lecture_Venus

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Astronomy

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Oct 30, 2023

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ES 2232F: Exploring the Planets An Introduction to Planetary Science Lecture: Inner Planets: Venus ES 2232F – Exploring the Planets Learning outcomes for Today! 1. Geology of Venus • What are the major geological features of Venus? • Does Venus have plate tectonics? 2. The Atmospheric History of Venus • What Venus like today? • How did Venus get so hot? Tour of the Solar System Inner Planets: Venus

ES 2232F – Exploring the Planets Venus • 2 nd planet from the sun • Earth’s twin (95% of diameter, 80% of mass) Nearly identical in size to Earth! • Hellish conditions due to an extreme greenhouse effect, the most intense greenhouse effect in Solar System • Surface hidden by clouds • Even hotter than Mercury: • Surface temp. 740 K (467 ° C), day & night! • Pressure = 90 bars ES 2232F – Exploring the Planets History Discovery – Known by the Ancients Roman Mythology – Named after the goddess of love and beauty – Shone brightest of the 5 planets known to the Ancients – Greek counterpart: Aphrodite (greek-mythology-pantheon.com)

ES 2232F – Exploring the Planets Exploration Mariner 2 – First successful mission to another planet – Launch: Aug. 27, 1962 – Goals: Fly by/gather info on atmosphere and surface Venera missions (1961 – 1984) – First to land and transmit photos from the surface of another planet – Probes survived < 2 hrs on surface Magellan (1989 – 1994) – Goals: Make quality radar maps of surface Venus Express (2005 – 2014) – Goals: Study the atmosphere – It was originally planned as a 500 days mission (NASA/JPL) (NASA/JPL) ES 2232F – Exploring the Planets Venera 13 (NSSDC)

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ES 2232F – Exploring the Planets Venus Express • First European spacecraft to orbit Venus • Major findings included evidence for past oceans on the surface Venus, 4 billion years ago; no water now • More lightning on Venus than Earth • Discovered a huge double atmospheric vortex at the south pole of Venus • Average cloud top wind speeds of 300 – 400 km/h • Lava flows as recent at 2.5 million years old; unknown if volcanoes are currently active ES 2232F – Exploring the Planets Double Vortex at South Pole (Courtesy ESA)

ES 2232F – Exploring the Planets Fact Sheet Distance from Sun 1.082 x 10 8 km (0.723 AU) Radius 6,051.8 km Mass 4.867 x 10 24 kg Density 5.243 g/cm 3 Surface gravity 8.87 m/s 2 Escape velocity 10,360 m/s Axial tilt 177.3 ° Rotation period (retrograde) 243.018 Earth days Orbital period 224.7 Earth days Surface temp. 735 K (462 ° C) ES 2232F – Exploring the Planets Internal structure Similar to Earth – Core : iron-rich – Mantle : Fe and Mg silicates – Crust : lighter silicate minerals – Atmosphere : carbon dioxide (CO 2 ) core mantle crust atmosphere

ES 2232F – Exploring the Planets Major Geologic Provinces Lowlands – Cover most of the planet (60%) – Few volcanoes – Resemble Earths oceanic floor, lunar maria, and northern lowlands of Mars Uplands – Isolated domes and broad swells – Transitional between lowlands and highlands – Volcanic features and coronae common Highlands – Cover < 15% of surface – Continent-like and resemble plateaus – Tectonic features common (tesserae) ES 2232F – Exploring the Planets Lowlands – purples/blues 0 ° E longitude 180 ° E longitude Highlands – reds/white Uplands – greens/yellows (NASA/JPL/USGS)

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ES 2232F – Exploring the Planets Tectonic features Rift valley Ridges (NASA/JPL) ES 2232F – Exploring the Planets Tesserae Complex system of ridges and grooves (NASA/JPL)

ES 2232F – Exploring the Planets Volcanic features • Numerous volcanoes • Many lava flows and extensive lava fields • Pancake-like domes (viscous lava) • Young surface (~500 My) – Resurfaced • No direct evidence for on going volcanic activity (NASA/JPL) Lava dome corona Lava channel Shield volcano All images: (NASA/JPL) Caldera

ES 2232F – Exploring the Planets Other surface features Aeolian features – Streaks: erosional and/or depositional features that are bright or dark – Dunes: evidence of sand on Venus – Yardings: ridges carved by wind erosion Impact cratering – Venus lacks heavily cratered terrain • Resurfacing events (volcanism) – Implies relatively young surface – Thick atmosphere burns up smaller meteors (NASA/JPL) ES 2232F – Exploring the Planets ES 2232F – Exploring the Planets (NASA/JPL)

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ES 2232F – Exploring the Planets Atmosphere Thick atmosphere – Extends ~50 km above surface – Carbon dioxide (CO 2 ) (96.4%) and nitrogen (N 2 ) (3.5%) • Trace amounts of SO 2 , H 2 O, CO, and H 2 S Greenhouse effect – Clouds reflect ~80% of Suns energy – Traps the rest in the atmosphere Pearson Education Inc. ES 2232F – Exploring the Planets Could there be life on Venus? • Published in Nature Astronomy (2020-2021) is an article suggesting the detection of Phosphine (PH 3 ) at 20 ppb in the clouds of Venus. There are also those who disagree! • Is this real? • There might be an overlap from the gas SO 2 causing a false signal. • Significance of phosphine – found in the gut of animals; associated with bacteria. • Not a naturally occurring compound on Earth.

ES 2232F – Exploring the Planets Future Missions • a joint mission of the European Space Agency and the Japan Aerospace Exploration Agency • launched on 20 th October 2018 and • is scheduled to begin orbiting Mercury on 5 th December 2025, after doing 2 flybys of Venus. ES 2232F – Exploring the Planets Tour of the Solar System: Venus: Our Twin Sister Summary: What have we learned today? What are the major geological features of Venus? Venus has cratering, volcanism, and tectonics but not much erosion. Does Venus have plate tectonics? The lack of plate tectonics on Venus is a mystery.

ES 2232F – Exploring the Planets Summary: What have we learned today? What is Venus like today? Venus has an extremely thick CO 2 atmosphere. Slow rotation means little weather. How did Venus get so hot? Runaway greenhouse effect made Venus too hot for liquid oceans. All carbon dioxide remains in atmosphere, leading to an extreme greenhouse effect. Tour of the Solar System: Venus: Our Twin Sister

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