<<

: Global warming gone bad & Venus: Sister ? Venus Earth

Mass 5x1024 kg 6x1024 kg a (semi- 0.7 AU 1 AU major axis) What is T at surface ~750 K ~300 K the boiling Temp of water? P at surface ~90 atm ~1 atm atm N2 and H2O CO2 and composition H2SO4 clouds How do we know Venus’s surface ? How do we know Venus’s surface temperature? high energy low energy short long wavelength “bluer” “redder” hot cold How do we know Venus’s surface temperature?

the emits Earth emits light here. T=6000 K here. T=300 K

Venus emits light here. T=750 How do we know what the clouds are made of?

Spectrum of with no

Amountlightof observed above the atmosphere

Wavelength of light (in the ) How do we know what the clouds are made of?

Spectrum of Spectrum of planet with no planet with atmosphere atmosphere

Wavelength at which a molecule in the atmosphere absorbs light

Amountlightof observed above the atmosphere Amountlightof observed above the atmosphere Wavelength of light (in the Wavelength of light (in the infrared) 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 . “Greenhouse” gases (like , water and methane) like to absorb in the infrared wavelengths. Planets emit light at infrared wavelengths (same as bodies). Conclusio n? “Greenhouse” gases don’t lett the heat from the planet escape. How did Venus get so hot?

A planet with no atmosphere

Solar Planetary radiation radiation comes in goes out

Planetary surface How did Venus get so hot? A planet with an atmosphere Solar radiation The greenhouse gases reradiate. comes in Some of the energy goes towards the surface. Greenhouse gases Planetary radiation goes out, but gets absorbed

Planetary surface 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 (, cows, rice)

Venus is an example of a “runaway greenhouse”.

greenhouse gases rocks and water heat the surface of the vaporize and release planet greenhouse gases

Why was Venus hot in the first place? Earth was also a “runaway greenhouse” at one point!

greenhouse gases rocks and water heat the surface of the vaporize and release planet greenhouse gases Why did the Earth cool, but Venus stay so hot? Why did the Earth cool, but Venus stay so hot?

Ideas: ? Biology?

It probably has to do with water, but why the Earth has water and Venus doesn’t is not well understood. It MAY be that water allowed to occur, and when the oceanic plates

subduct, they take CO2 with them.

The Surface of Venus

Venus’s surface can’t be viewed in visible light. The atmosphere absorbs most visible light. Radio light reaches the surface. Venus’s surface was mapped with .

RADAR instrument

surface

RADAR instruments can map topography. Venus’s surface was mapped with RADAR.

RADAR instrument

smooth rough surface surface RADAR instruments can determine roughness. Venus’s surface was mapped with RADAR.

RADAR instrument

Reflective surface Absorptive surface RADAR instruments can determine reflectivity. Venus’s has few small craters. Why?

Venus’s has few large craters. Why? Venus’s has few small craters. Why? Venus has a dense atmosphere. Venus’s has few large craters. Why? Venus’s surface is ‘young’. How are craters on Venus different from craters on other bodies?

the Venus Venus’s surface is covered with volcanic features.

How can you tell impact craters from volcanic ? What does the brightness mean in these images? Venus’s surface is covered with volcanic features. Few craters have been altered by . What does this mean?

If lava lies over an existing crater, then the crater came first. Venus: Take-away messages

• Venus’s bulk properties (, size, distance from sun) are similar to Earth.

• However, Venus’s 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. • is an important process on its surface, but may not have been active recently. • Venus’s entire surface is ‘young’, so some global resurfacing event occurred.