Astronomy Lecture Notes
October 12 2012
- Moon: slow rotation, solid, rocky core no field.
- Mercury: slow rotation and solid but metallic does not have a magnetic field.
- Mars: weak gravity but cool temperature atmosphere.
- Atmosphere: mostly CO2 because no rain to wash it out, no plants to convert it.
- No erosion heavily cratered.
- Interior: small, metallic core, probably solid No magnetic field, no continental
- Surprises: Huge volcanoes, large rifts, evidence of flowing water, ice.
- Venus: a twin of Earth?
Is Venus a twin of Earth?
NO! not even close.
Atmosphere: 96% CO2 (not O2 or N2).
Surface temperature: 470 degree Celsius (743 K) hotter than pizza oven.
Why is Venus so different?
It is slightly closer to the Sun than Earth, makes a big difference.
o Have volcanoes that we assume to emit CO2 and H2O like Earth’s
But Venus is too HOT for liquid water to form…
No rain to wash CO2 from atmosphere.
CO2 is a powerful GHG
Makes it much hotter.
NOTE: Earth’s rocks have as much CO2 as Venus has in its atmospheres Rain
removed that much CO2 from our atmosphere.
ALL of this because Venus is a bit closer to the Sun.
Extreme heat no water, rain, or oceans.
o No plants to convert CO2 to O2
o Without O2 no ozone (O3)
Cannot block ultra violet radiation.
Ultraviolet radiation blocks H2O molecules in the
atmosphere Hydrogen and Oxygen atoms.
o Hydrogen escapes to space.
o Oxygen binds with soil.
What is the surface of Venus like?
Problem: the atmosphere is very thick and cloudy we can’t see the
The surface temperature is so hot and the pressure is so high that all landers
SOULUTION: using satellites orbiting Venus to study the surface using radar
to see through.
Volcanoes and lava flows
o Consistent with Venus’ size and mass. Astronomy Lecture Notes
October 12 2012
Large impact craters
o Not eroded by water, ice, wind
Almost no signs of continental drift
o No mountain range
o Few faults or rift
VERY different from Earth.
Maybe continental drift needs water to lubric