ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections...
-
Upload
bennett-walsh -
Category
Documents
-
view
219 -
download
0
Transcript of ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections...
![Page 1: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/1.jpg)
ASTR100 (Spring 2008) Introduction to AstronomyEarth as a Planet
Prof. D.C. Richardson
Sections 0101-0106
![Page 2: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/2.jpg)
The Greenhouse Effect
Certain molecules let sunlight through but trap escaping infrared photons.
(H2O, CO2, CH4)
![Page 3: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/3.jpg)
The Greenhouse Effect
![Page 4: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/4.jpg)
Greenhouse Effect: Bad?
The Earth is much warmer because of the greenhouse effect than it would be without an atmosphere……but so is Venus.
![Page 5: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/5.jpg)
Why is the sky blue?
The atmosphere scatters blue light from the Sun, making it appear to come from all directions.
Sunsets are red because less of the red light from the Sun is scattered.
![Page 6: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/6.jpg)
Planetary magnetic fields
Moving charged particles create magnetic fields.
So can a planet’s interior, if the core is electrically conducting, convecting, and rotating, i.e., hot!
![Page 7: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/7.jpg)
Earth’s Magnetosphere
Earth’s magnetic fields protects us from charged particles from the Sun.
The charged particles can create aurorae (e.g., the “Northern lights”).
![Page 8: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/8.jpg)
If a planet’s core is cold, do you expect it to generate magnetic
fields?
A. Yes, refrigerator magnets are cold, and they have magnetic fields.
B. No, planetary magnetic fields are generated by moving charges around, and if the core is cold, nothing is moving.
![Page 9: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/9.jpg)
If a planet’s core is cold, do you expect it to generate magnetic
fields?
A. Yes, refrigerator magnets are cold, and they have magnetic fields.
B. No, planetary magnetic fields are generated by moving charges around, and if the core is cold, nothing is moving.
![Page 10: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/10.jpg)
ASTR100 (Spring 2008) Introduction to AstronomyThe Other Terrestrial Worlds
Prof. D.C. Richardson
Sections 0101-0106
![Page 11: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/11.jpg)
Was there ever geological activity on the Moon or
Mercury?
![Page 12: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/12.jpg)
Moon
Some volcanic activity 3 billion years ago must have flooded lunar craters, creating lunar maria.
The Moon is now geologically dead.
Impact Flooding Mare Humorum
Before
![Page 13: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/13.jpg)
Cratering of Mercury
Mercury has a mixture of heavily cratered and smooth regions like the Moon.
The smooth regions are likely ancient lava flows.
![Page 14: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/14.jpg)
Tectonics on Mercury
Long cliffs indicate Mercury shrank early in its history.
Mercury is now geologically dead.
Shrinkage not to scale!
![Page 15: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/15.jpg)
Messenger at Mercury
• First flyby Jan 14, 2008.
• Will enter orbit Mar 19, 2011.
• First views of unseen side.
![Page 16: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/16.jpg)
Mars versus Earth
50% Earth’s radius, 10% Earth’s mass.
1.5 A.U from the Sun. Axis tilt about the same as Earth.
Similar rotation period. Thin CO2 atmosphere: little greenhouse.
Main difference: Mars is smaller.
![Page 17: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/17.jpg)
Seasons on Mars
Seasons on Mars are more extreme in the southern hemisphere because of its elliptical orbit.
![Page 18: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/18.jpg)
Storms on Mars
Seasonal winds on Mars can drive huge dust storms.
![Page 19: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/19.jpg)
What geological features tell us water once flowed
on Mars?
![Page 20: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/20.jpg)
Surface of Mars appears to have ancient river beds.
![Page 21: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/21.jpg)
Closeup of a crater perhaps eroded by water.
![Page 22: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/22.jpg)
![Page 23: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/23.jpg)
Volcanoes…as recent as 180 million years ago…
![Page 24: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/24.jpg)
Past tectonic activity…
![Page 25: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/25.jpg)
Low-lying regions may once have had oceans.
![Page 26: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/26.jpg)
Low-lying regions may once have had oceans.
![Page 27: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/27.jpg)
OpportunitySpirit
![Page 28: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/28.jpg)
• 2004: Opportunity Rover provided strong evidence for abundant liquid water on Mars in the distant past.• How could Mars have been warmer and wetter in the past?
The Rovers
![Page 29: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/29.jpg)
Today, most water lies frozen underground (blue regions)…
![Page 30: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/30.jpg)
Why did Mars change?
![Page 31: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/31.jpg)
Climate Change on Mars
Mars has not had widespread surface water for 3 billion years.
The greenhouse effect probably kept the surface warmer before that.
Somehow Mars lost most of its atmosphere…
![Page 32: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/32.jpg)
Climate Change on Mars
Magnetic field may have preserved early Martian atmosphere.
Solar wind may have stripped atmosphere after field decreased because of interior cooling.
![Page 33: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/33.jpg)
Is Venus geologically active?
![Page 34: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/34.jpg)
Cratering on Venus
Impact craters, but fewer than Moon, Mercury, Mars.
![Page 35: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/35.jpg)
Volcanoes on Venus
Many volcanoes, including both shield volcanoes and stratovolcanoes.
![Page 36: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/36.jpg)
Tectonics on Venus
Fractured and contorted surface indicates tectonic stresses.
![Page 37: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/37.jpg)
Erosion on Venus
Photos of rocks taken by landers show little erosion.
![Page 38: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/38.jpg)
Does Venus have plate tectonics?
Most of Earth’s major geological features can be attributed to plate tectonics, which gradually remakes Earth’s surface.
Venus does not appear to have plate tectonics, but its entire surface appears to have been “repaved” 750 million years ago.
![Page 39: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/39.jpg)
Why is Venus so hot?
![Page 40: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/40.jpg)
Why is Venus so hot?
The greenhouse effect on Venus keeps its surface temperature at 470˚C.
But why is the greenhouse effect on Venus so much stronger than on Earth?
![Page 41: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/41.jpg)
Atmosphere of Venus
Venus has a very thick carbon dioxide atmosphere with a surface pressure 90 times that of Earth.
Thick atmosphere produces an extremely strong greenhouse effect.
![Page 42: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/42.jpg)
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?
Where is Earth’s CO2?
![Page 43: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/43.jpg)
What would happen if…
What would happen if Earth were moved to Venus’ orbit?
It would get hot!
How would the initial heating affect the oceans and the greenhouse effect?
It would get hotter!
![Page 44: ASTR100 (Spring 2008) Introduction to Astronomy Earth as a Planet Prof. D.C. Richardson Sections 0101-0106.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649d045503460f949d7e56/html5/thumbnails/44.jpg)
Runaway Greenhouse Effect
Eventually H2O breaks down and H escapes into space, as apparently happened on Venus.