17 Mercury&Venus
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Transcript of 17 Mercury&Venus
7/23/2019 17 Mercury&Venus
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Terrestrial Worlds 1
Mercury, Venus,
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Mercury basics
• Closest to Sun (0.4 AU), 10th largest world
• Orbit -88 Earth days
• Surface gravity -3.7 m/s2
(38% of Earth)• 10-14 bars of pressure (negligible)
• Temperatures- 800 oF in day (second hottest)
- -300 oF at night• Weak magnetic field
• Spacecraft- Mariner 10
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Mercury’s Surface
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Mercury’s Surface
• A mixture of heavily cratered and smoothregions like the Moon
• Smoother regions are likely ancient lava flows
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Caloris basin
Multi-ring impact basin
(Only half visiblefrom Mariner 10)
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Caloris basin MESSENGER 2009 -1550km
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Volcanism on Mercury
• ancient lava flows, no large floods
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Mercury-Discovery
Rupes
A fault scarp
caused by cooling
and shrinking of
Mercury
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Mercury- Lobate Scarps fault scarps mostly run N-S, can be up to 2000 ft high
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Tectonics on Mercury
Mapping the location and size of the scarps tells how muchMercury has shrunk.
Current numbers suggest Mercury's radius has lost 1.5 km
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Mercury Atmosphere
• Sensitive measurements show Moon andMercury have extremely thin atmospheres
• Gas comes from impacts that eject surface atoms
MoonMoon MercuryMercury
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VENUS
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Venus basics
• 2nd planet from Sun (0.7 AU), 6th largest world.• Orbit -224 Earth days
• Sidereal rotation -243 Earth days (solar day-117 Eds)
• Surface gravity-8.8 m/s2 (90 of Earth)
• 90 bars of pressure (90 x Earth)
• 96% CO2 3.5% N2 < 1% others
• Venus is the hottest planet. 870 oF
• Intense cloud cover - highly reflective in visible light,surface unseen except by radar
• Spacecraft- Pioneer, Magellan (USA)
Venera 9-16 (Russia)
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Venus As
Seen in
Radar
light
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Highlands on Venus- Aphrodite Terra
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Venus - Chasma
Vast mountain and canyon systems.
-3km high and 3km deep running
for thousands of miles
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Venus-Regios
RegionsWhere
canyon
systems
join at a
high volcano
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Tectonics• Downwelling
-Highlands and faultedregions called tessera
• Upwelling
-Extension rifts at hot spots= chasmas and regios
Crust too strong to
break all the way
through. No plate
tectonics
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Volcanism on Venus
• 80% of Venus is resurfaced by volcanism
• Volcanic shapes controlled by height and
location.
• Hot spots -large shield volcanoes.
• Lowlands - volcanic floods.
• Middling heights- fields of cinder cones.
• High areas - lava too hard to rise - coronae
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Venus Regios - Volcanic hotspots
C F il d l
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Coronae -Failed volcanoeslava tries & fails to break the surface in the mountains,
-leaves a circular depression (unique to Venus)
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Surface of Venus
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Venus Surface Processes - WindWind streak showing wind direction
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Venus Cratering
• Lots of small to middle-sized craters, fewlarge ones
• Even distribution -Most of Venus’ surfacehas a similar age
• Most of Venus resurfaced by catastrophiclava flooding < 1 billion yrs ago.
• Current activity??
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Venus Atmosphere
• 90 bars of pressure (90 x Earth)
• 96% CO2
• Massive greenhouse warming.
• Clouds- sulfuric acid!
• Slow rotation - almost no coriolis effect.
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• Venus closer to the Sun than Earth, plusrotation is too slow for a magnetic field.
! Initial water would vaporize.
• Runaway greenhouse effect made Venus
too hot for liquid oceans
• All carbon dioxide remains in atmospheremaintaining a huge greenhouse effect
Why No Oceans?