Chapter 7dHothouse Venus

Venus• Orbital distance:

– 108 200 000 km (0.72 AU)– NOT Eccentric

• Year:– 224.7 d

• Day:– -243.018 d– Retrograde rotation

• Temperature:– Max: 475oC

• 887 degrees Fahrenheit

– Min: 450oC • 842 degrees Fahrenheit

• Diameter:– 12 103.6 km

• Density:– 5.204 g/cm3

• Composition:– Uncertain, but seems

similar to Earth– Very dense atmosphere

• Axial Tilt: 177.3o

• Moons: none• Other:

– No magnetic field, possibly due to slow rotation

7.4 Venus: A Hothouse World

• Our Goals for Learning• Is Venus geologically active?• Why is Venus so hot?

Is Venus geologically active?

Is Venus geologically active?

Radar images show lots of volcanic & tectonic features, as expected for a large terrestrial planet

Why is Venus so hot?

Greenhouse effect.

But why is it so prominent on Venus?

Thick CO2 atmosphere of Venus locks heat in

Where is Earth’s CO2?

Where is Earth’s CO2?

Rocks - like limestone(and some in plant life and in the ocean)

Why did this happen on Earth and not on Venus?

Venus lacks oceans to dissolve the carbon dioxide and lock it away in rock on the seafloor

And why is that?

We can understand Venus’ history by thinking about what would happen if Earth were moved to Venus’ orbit.

How would the initial heating affect the oceans and the greenhouse effect?

A runaway greenhouse effect would then occur.Eventually, water molecules would break down & escape to space, just as apparently happened on Venus

What have we learned?• Is Venus geologically

active?• Venus almost certainly

remains geologically active today. Its surface shows evidence of major volcanic or tectonic activity in the past billion years, and it should retain nearly as much internal heat as Earth. However, geological activity on Venus differs from that on Earth in at least two key ways: lack of erosion and lack of plate tectonics.

• Why is Venus so hot?• Venus’s extreme surface

heat is a result of its thick, carbon dioxide atmosphere, which creates a very strong greenhouse effect. The reason Venus has such a thick atmosphere is its distance from the Sun: It was too close to develop liquid oceans like those on Earth, where most of the outgassed carbon dioxide dissolved in water and became locked away in rock. Thus, the carbon dioxide remained in the atmosphere, creating the strong greenhouse effect.