Venus: Global warming gone bad Earth & Venus: Sister planets? Venus Earth Mass 5x1024 kg
6x1024 kg a (semimajor axis) 0.7 AU 1 AU T at surface ~750 K
~300 K P at surface ~90 atm ~1 atm atm N2 and H2O CO2 and composition clouds H2SO4 clouds
What is the boiling Temp of water? How do we know Venuss surface temperature? How do we know Venuss surface temperature? high energy
low energy short wavelength long wavelength bluer redder hot
cold How do we know Venuss surface temperature? the Sun emits light here. T=6000 K Earth emits light here. T=300 K
Venus emits light here. T=750 Amount of light observed above the atmosphere How do we know what the clouds are made of? Spectrum of planet with no atmosphere
Wavelength of light (in the infrared) Spectrum of planet with no atmosphere Wavelength of light (in the infrared)
Amount of light observed above the atmosphere Amount of light observed above the atmosphere How do we know what the clouds are made of? Spectrum of planet with atmosphere
Wavelength at which a molecule in the atmosphere absorbs light Wavelength of light (in the infrared) How do we know what the clouds are made of? (Infrared light)
How did Venus get so hot? Remember - all gases absorb light at specific wavelengths. Greenhouse gases (like carbon dioxide, water and methane) like to absorb in the infrared wavelengths. Planets emit light at infrared wavelengths (same as human bodies). Conclusion? Greenhouse gases dont lett the heat from the planet escape. How did Venus get so hot?
A planet with no atmosphere Solar radiation comes in Planetary surface Planetary radiation
goes out How did Venus get so hot? A planet with an atmosphere Solar radiation comes in The greenhouse gases reradiate. Some of the energy
goes towards the surface. Greenhouse gases Planetary surface Planetary radiation goes out, but gets
absorbed How do greenhouse gases get into the atmosphere? Water: evaporation CO2: vaporization of rocks, release from traps, vaporization of biotic material (like fossil fuels), respiration Methane: release from traps, biology (bacteria, cows, rice)
Venus is an example of a runaway greenhouse. rocks and water vaporize and release greenhouse gases greenhouse gases heat the surface of the planet Why was Venus hot in the first place?
Earth was also a runaway greenhouse at one point! rocks and water vaporize and release greenhouse gases greenhouse gases heat the surface of the planet
Why did the Earth cool, but Venus stay so hot? Why did the Earth cool, but Venus stay so hot? Ideas: Oceans? Biology? It probably has to do with water, but why the Earth has water and Venus doesnt is not well understood. It MAY be that water allowed plate tectonics to occur, and when the oceanic plates subduct, they take CO2 with them.
The Surface of Venus Venuss surface cant be viewed in visible light. The atmosphere absorbs most visible light. Radio light reaches the surface. Venuss surface was mapped with RADAR. RADAR instrument surface
RADAR instruments can map topography. Venuss surface was mapped with RADAR. RADAR instrument smooth surface rough
surface RADAR instruments can determine roughness. Venuss surface was mapped with RADAR. RADAR instrument Reflective surface Absorptive
surface RADAR instruments can determine reflectivity. Venuss has few small craters. Why? Venuss has few large craters. Why? Venuss has few small craters. Why? Venus has a dense atmosphere. Venuss has few large craters. Why?
Venuss surface is young. How are craters on Venus different from craters on other bodies? the moon Venus Venuss surface is covered with volcanic features. How can you tell impact craters
from volcanic calderas? What does the brightness mean in these images? Venuss surface is covered with volcanic features. Few craters have been altered by lava. What does this mean? If lava lies over an existing crater,
then the crater came first. Venus: Take-away messages Venuss bulk properties (mass, size, distance from sun) are similar to Earth. However, Venuss atmosphere has a lot of CO2 and therefore its surface is very hot. Exactly why Venus and Earth evolved in different ways is not well understood, but is probably related to water. Volcanism is an important process on its surface, but
may not have been active recently. Venuss entire surface is young, so some global resurfacing event occurred.
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