Download Venus

Quiz #8: Monday, November 21
emphasis on Chapter 21 (Moon and Mercury)
Homework due Monday:
Chp. 22:
Review questions 3, 4
Discussion question 1
Learning to Look 1
1
Wednesday, November 16, 2011
Mercury, Day 1
October 2011
MESSENGER
Wednesday, November 16, 2011
2
How is the planet Mercury
different than Earth's moon?
1.
2.
3.
4.
5.
The lowland maria on
Mercury are not much darker
than the cratered highlands.
Mercury has a much higher
density.
Mercury has a dipole
magnetic field.
The lowland maria on
Mercury are not much darker
than the cratered highlands;
and Mercury has a much
higher density.
all of these choices
Wednesday, November 16, 2011
How do we suppose that the lobate
scarps on Mercury's surface formed?
1.
Lobate scarps are huge,
dormant lava tubes.
2.
As Mercury cooled and shrank,
the crust wrinkled.
3.
Plate tectonics created a chain
of folded mountains.
4.
One side along a strike-slip
boundary was forced upward.
5.
As a chain of volcanic
mountains along the edge of a
subduction zone.
Wednesday, November 16, 2011
5
Wednesday, November 16, 2011
6
Wednesday, November 16, 2011
The Interior of Mercury
Large, metallic core.
Over 60% denser than Earth’s moon
Magnetic field only
~ 0.5 % of Earth’s magnetic field.
Wednesday, November 16, 2011
Artistic rendering of Mercury’s collisional past
8
Wednesday, November 16, 2011
9
Wednesday, November 16, 2011
Chapter 22
Comparative Planetology
of Venus and Mars
Wednesday, November 16, 2011
Outline
I. Venus
A. The Rotation of Venus
B. The Atmosphere of Venus
C. The Venusian Greenhouse
D. The Surface of Venus
E. Volcanism on Venus
F. A History of Venus
II. Mars
A. The Canals of Mars
B. The Atmosphere of Mars
C. The Geology of Mars
D. Finding the Water on Mars
E. A History of Mars
III. The Moons of Mars
A. Origin and Evolution
Wednesday, November 16, 2011
12
Wednesday, November 16, 2011
Why might we expect Venus
and Earth to be similar?
1.
2.
3.
4.
5.
Both planets are about the
same size and density.
Both planets have about the
same chemical composition.
Both planets have about the
same atmospheric
composition.
Both planets are about the
same size and density; and
both planets have about the
same chemical composition.
all of these choices
Wednesday, November 16, 2011
Why might we expect Venus
and Earth to be similar?
1.
2.
3.
4.
5.
Both planets are about the
same size and density.
Both planets have about the
same chemical composition.
Both planets have about the
same atmospheric
composition.
20%
Both planets are about the
same size and density; and
both planets have about the
same chemical composition.
all of these choices
Wednesday, November 16, 2011
20%
20%
20%
Venus:
• Similar to Earth in size.
• Perpetually covered by thick
clouds. Cannot see surface!
• Surface temperature: 900F;
hot enough to melt lead!
• Surface pressure very high:
would feel like you’re 3000 ft
under the ocean!
•No water on surface
• Rotation is slowest of all
planets: 243 days.
• Few craters
14
Wednesday, November 16, 2011
Measuring Venus’ rotation by radar: rotation
period nearly equals spin period
a= 0.723 AU
Orbital period = 224.7 days
Rotation period = 243.0 days
Slow rotation: weak magnetic field
Sun rises in the “west” and sets in the “east”
-retrograde spin!!
15
Wednesday, November 16, 2011
Why would one expect Venus to
have a molten metallic interior?
1.
2.
3.
4.
5.
Because it is younger than
Earth.
Because it is closer to the
Sun than our planet.
Because its atmosphere is
mainly composed of carbon
dioxide.
Because of its dense
atmosphere.
Because it is almost of the
size of Earth, and planets of
that size cool slowly.
Wednesday, November 16, 2011
The Atmosphere of Venus
4 thick cloud layers
(→ surface invisible to us
from Earth).
Extremely inhospitable:
96 % carbon dioxide (CO2)
3.5 % nitrogen (N2)
Very efficient “greenhouse”!
Very stable circulation patterns with
high-speed winds (up to 240 km/h)
17
Wednesday, November 16, 2011
Human Effects on Earth’s Atmosphere
1) The Greenhouse Effect
Earth’s surface is heated by the
sun’s radiation.
Heat energy is re-radiated from
Earth’s surface as infrared radiation.
CO2, but also other gases in the
atmosphere, absorb infrared light
→ Heat is trapped in the
atmosphere.
This is the Greenhouse Effect.
The Greenhouse Effect occurs naturally
and is essential to maintain a
comfortable temperature on Earth,
but human activity, in particular
CO2 emissions from cars and
industrial plants, is drastically
increasing the concentration of
greenhouse gases.
Wednesday, November 16, 2011
Earth’s Atmosphere
1) Outgassing: Release of gasses bound in compounds in the
Earth’s interior through volcanic activity
2) Bombardment with icy meteoroids and comets
3) Chemistry (carbon cycle), Radiation (ozone)
4) Life (oxygen)
Wednesday, November 16, 2011
Water
About 2/3 of Earth’s
surface is covered
by water.
Wednesday, November 16, 2011
The Earth’s Carbon Cycle
21
Wednesday, November 16, 2011
Venus vs. Earth
Both had same initial atmosphere.
Venus closer to Sun where too hot for liquid
water.
Venus lost its oceans within first ~600 million
years.
No carbon sink available in for of oceans.
Large CO2 content in atmosphere.
Runaway greenhouse effect.
Earth’s atmosphere also influenced by life.
If we could untrap all of Earth’s carbon, our
atmosphere would be very similar to Venus’.
22
Wednesday, November 16, 2011
How do we know what the
surface of Venus looks like?
1.
Large Earth-based optical
telescopes have photographed
the surface.
2.
The high resolution of the
Hubble Space Telescope
reveals the surface details.
3.
Radar mapping at radio
wavelengths allows us to
determine surface elevations.
4.
Orbiting spacecraft have imaged
the surface at ultraviolet and
infrared wavelengths.
5.
Two spacecraft that entered the
atmosphere of Venus released
balloons that floated just
beneath the cloud deck and
mapped the surface.
Wednesday, November 16, 2011
Surface Topology
Global radar map of Venus (Pioneer; 1978)
24
Wednesday, November 16, 2011
Highlands
Smooth lowlands
Wednesday, November 16, 2011
Highland
regions:
Maxwell
Montes are
~ 50 %
higher than
Mt. Everest!
Radar Map of Venus’s Surface
Global radar map
of Venus
(Magellan;
1989-1994;
4 years to
produce)
• Scattered
impact craters
•
Volcanic
regions
•
Smooth lava
flows
Wednesday, November 16, 2011
Results of Magellan Radar Maps:
• low, gently rolling plains
• “continental” highlands: 8% of surface area (Earth’s
continents make up 45% of surface area).
• volcanic peaks, wrinkled crust
• No evidence of plate tectonics (rifts, trenches, mountains)
• Very few craters: surface is “young”.
• Numerous uplifted surface regions (hot spots; not
associated with plate tectonics)
27
Wednesday, November 16, 2011
Volcanism on Earth
Volcanism on Earth is commonly
found along subduction zones
(e.g., Rocky Mountains).
This type of volcanism is not found on Venus or Mars.
Wednesday, November 16, 2011
Shield Volcanoes
Found above
hot spots:
Fluid magma
chamber, from
which lava erupts
repeatedly through
surface layers
above.
All volcanoes on Venus and Mars are shield volcanoes
Wednesday, November 16, 2011
Shield Volcanoes (2)
Tectonic plates moving over hot spots producing
shield volcanoes → Chains of volcanoes
Example: The
Hawaiian Islands
Wednesday, November 16, 2011
Volcanism on Venus
Sapas Mons (radar image)
~ 400 km (250 miles)
2 lava-filled calderas
Lava flows
Wednesday, November 16, 2011
Volcanic Features on Venus
Baltis Vallis: 6800 km long
lava flow channel (longest
in the solar system!)
Some lava flows collapsed after
molten lava drained away
Aine
Corona
Coronae: Circular bulges formed by
volcanic activity
Pancake
Domes:
Associated
with volcanic
activity forming
coronae
Wednesday, November 16, 2011
Volcanic Features on Venus
Aine
Corona
Some lava flows collapsed after
molten lava drained away
Coronae: Circular bulges formed by
volcanic activity
Pancake
Domes:
Associated
with volcanic
activity forming
coronae
Wednesday, November 16, 2011
Pancake Domes: congealed lava flows
33
Wednesday, November 16, 2011
34
Wednesday, November 16, 2011
Lakshmi Planum and Maxwell Mountains
Radar image
Wrinkled mountain formations indicate compression
and wrinkling, though there is no evidence of plate
tectonics on Venus.
Wednesday, November 16, 2011
The Surface of Venus
Venera 13 photograph of surface of Venus (1970):
Wednesday, November 16, 2011
Russian Venera (1970):
flat, brocken rocks, orange glow of sunlight diffusing
through clouds. Rocks are volcanic. Lander lasted
two hours!
37
Wednesday, November 16, 2011
Differences between Earth/Venus surface features
Earth: plate tectonics (rifting, subduction,
mountains), “older” surfaces
Venus: surface dominated by (relatively young)
congealed lava flows; entire surface has
been recently (within last 700 million
years) re-paved.
38
Wednesday, November 16, 2011
Tectonic Plates
Earth’s crust is composed of several distinct tectonic plates, which
are in constant motion with respect to each other → Plate tectonics
Evidence for plate tectonics can
be found on the ocean floor
Wednesday, November 16, 2011
… and in geologically active
regions all around the Pacific
Active Zones Resulting from
Plate Tectonics
Volcanic hot spots due to
molten lava rising up at plate
boundaries or through holes in
tectonic plates
Wednesday, November 16, 2011
All of the dormant volcanoes on Venus and Mars are the
shield type, and many are much larger than any shield
volcano on Earth. What does this tell us about Venus and
Mars?
1.
2.
3.
4.
5.
Venus and Mars both have
plate tectonics.
Neither Venus nor Mars has
plate tectonics.
Their interiors are at a higher
temperature than Earth's
interior.
Their interiors are at a lower
temperature than Earth's
interior.
Venus and Mars both have
carbon dioxide atmospheres.
Wednesday, November 16, 2011