atmospheres of the terrestrial planets. atmospheres of the moon and mercury the moon mercury there...
TRANSCRIPT
Atmospheres of the Moon and Mercury
The Moon
Mercury
There is no substantial atmosphere on either body
They probably had outgassing long ago Without replenishment, these gases were lost
But they have been geologically dead for
billions of years
The low surface gravity of the Moon and Mercury make it very easy for molecules to escape
But they do currently have an extremely thin gas around them – an EXOSPHERE(One hundred trillion times thinner than Earth’s atmosphere!)
These images were made by instruments that are sensitive to sodium emission lines
These gases come from impacts by micrometeorites, solar wind particles, and high energy photons
Some of those escape directly into space, others fall back to the surface
Those that fall back typically bounce a few dozen times before being reabsorbed into the
surface
This leads to an interesting phenomenon…
The gas particles are most easily ejected where the
surface is warmed by sunlight
The bouncing will come to an end when a particle hits a very cold part of the surface
Polar craters that are in perpetual shadow
Water ice has been found in many of these craters
What is the source of the exospheres of the Moon and Mercury?
A) evaporation and sublimation from surface ices and liquids
B) impacts on the surface by solar wind particles
C) meteoroid impacts on the surface
D) volcanic outgassing
E) B and C
The Atmospheric History of Mars
Very thin atmosphere
Average temperature ~ – 50° C
No oxygen no ozone layer
UV hits the surface
Astronauts could not survive without a pressurized spacesuit
While there can be no liquid water on the surface, there IS water ice.
The Phoenix lander landed right on top of a patch of water ice
So what happened to Mars’ atmosphere?
Warm interior allowed:• Liquid core magnetic field• Active volcanism outgassing• Thicker atmosphere stronger
greenhouse effect• Thick, warm atmosphere liquid water
Cooled interior:• No core convection no magnetic field• No active volcanism no outgassing• Thinner atmosphere weaker
greenhouse effect• Thin, cold atmosphere no liquid water
Size was the primary factor here
How do seasons on Mars differ from seasons on Earth?
A) They are less extreme because of Mars's smaller axis tilt.
B) They are more extreme because of Mars's greater axis tilt.
C) They are less extreme because of Mars's larger orbit.
D) They are more extreme because of Mars's larger orbital eccentricity.
E) Seasons on Earth and Mars are basically the same.
The Atmospheric History of VenusVery thick atmosphere: 90 bar
(Equivalent to 0.6 mi under water)
Average temperature:870° F = 465° C
Everywhere, all the time
At high altitudes, temps are ~ 65° C
Sulfuric acid clouds and rain:It evaporates before reaching the
ground
High altitude winds circle planetin 4 days:
> 200 mph!
Being about the same size as Earth, and forming near it in the solar nebula, Venus should have been made of the same stuff
Why would it end up with LOTS of carbon dioxide in its atmosphere and almost no water?
The Atmospheric History of Earth
If Earth started out so similar to Venus and Mars, how did
it end up so different?
What is the most abundant gas in Venus’s atmosphere?
A) Oxygen
B) Nitrogen
C) Water vapor
D) Carbon dioxide
E) Argon
What is the most abundant gas in Earth’s atmosphere?
A) Oxygen
B) Nitrogen
C) Water vapor
D) Carbon dioxide
E) Argon
What is the second most abundant gas in Earth’s atmosphere?
A) Oxygen
B) Nitrogen
C) Water vapor
D) Carbon dioxide
E) Argon
While Earth has gone through ice ages and even “snowball” phases,the CO2 thermostat has pulled Earth out of those cold times
And now we’re interfering with that thermostatWe’re releasing CO2 at a rate over 100 times faster than volcanoes
The rise in CO2 is undeniable – as is the fact that it has never happened so fast
Average global temperatures are also rising
Only models that include human release of greenhouse
gases match the observed temperature increase
It IS a result of human activity
Where is most of Earth’s carbon dioxide?
A) In the atmosphere
B) In the oceans
C) In the rainforests
D) In rocks
2) On which terrestrial world is nitrogen the primary component of the atmosphere?
Mercury
Venus
Earth
The Moon
Mars
4) Earth’s CO2 cycle has pulled Earth out of “snow ball” phases because …
A) The rate of CO2 removal from the atmosphere goes down slightly, increasing greenhouse gas concentrations in the atmosphere.
B) CO2 removal stops completely, increasing greenhouse gas concentrations in the atmosphere.
C) The rate of CO2 removal from the atmosphere goes up slightly, decreasing greenhouse gas concentrations in the atmosphere.
D) CO2 outgassing stops completely, decreasing greenhouse gas concentrations in the atmosphere.