Fig. 6-37, p.119

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Fig. 6-37, p.119
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Fig. 6-41, p.122
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Fig. 6-1, p.97
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VENUS EARTHS SISTER PLANET?

• SIMILAR DISTANCE FROM THE SUN
• Earth 1 AU Venus 0.7 AU
• SIMILAR DIAMETERS
• Venus is about 95 the diameter of the Earth.
  Earth 12,756km Venus 12,140km
• SIMILAR MEAN DENSITIES.
• Earth 5.5gm/cm3 Venus 5.2gm/cm3
• SIMILAR TOTAL MASS
• BOTH HAVE ATMOSPHERES Venus atmosphere was
  discovered by Mikhail Lomonosov during the
  transit of 1761
• Venus dense cloud cover constantly prevents
  visual observations of its surface.

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TRANSITS OF THE SUN FOR MERCURY AND
VENUS Transits occur when an Inferior
planet passes in front of the Sun as seen
from Earth
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Fig. 6-38, p.119
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Fig. 6-37, p.119
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Fig. 6-41, p.122
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Venus' Magnetic Field

• Venus has no detectable magnetic field.
• The lack of a magnetic field leaves no protection
  from the solar wind.
• The upper atmosphere deflects the high energy
  particles to form an ion tail.

Figure 22.11
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Venus Properties

• Venus rotates backwards.
• It may have been 'knocked' over as the result of
  a collision.
• Venus doesn't have a moon.
• Without a moon to gravitationally tug on the
  planet, it could have precessed over as does a
  spinning top.

Figure 22.1A
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The Rotation of Venus

• Almost all planets rotate counterclockwise, i.e.
  in the same sense as orbital motion.

• Exceptions Venus, Uranus and Pluto

• Venus rotates clockwise, with period slightly
  longer than orbital period.

Possible reasons

• Off-center collision with massive protoplanet

• Tidal forces of the sun on molten core

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The Atmosphere of Venus
4 thick cloud layers (? surface invisible to us
from Earth).
UV image
UV image
Very stable circulation patterns with high-speed
winds (up to 240 km/h)
Extremely inhospitable
96 carbon dioxide (CO2)
Very efficient greenhouse!
3.5 nitrogen (N2)
Rest water (H2O), hydrochloric acid (HCl),
hydrofluoric acid (HF)
Extremely high surface temperature up to 745 K
( 880 oF)
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Figure 22.1b
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Figure 22.3
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Venus Radar Images
Figure 22.5

• Whole planet radar shows rolling plains and
  highland regions.
• There is no surface water on Venus.
• There is little erosion on its surface.

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Venus' Surface
Figure 22.2A

• The surface of Venus, shown here, resembles a
  landscape of shale.
• This is a small area around the Venera spacecraft.

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Lava Flow
Figure 22.4

• This example of a 1000 year old lava flow near
  Flagstaff, Arizona, resembles what some parts of
  Venus might look like.
• These rough flows appear bright in radar images.
• Radar images of Venus show similar bright areas.

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Impact Crater Howe
This is a radar image of the impact crater Howe.
Figure 22.6
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Volcano Sapas Mons

• This is an image of the volcano, Sapas Mons,
  which has been digitally modified.
• The view seen here is almost terrestrial.

Figure 22.7A
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Volcano Aine Corona

• Familiar, earth-like geology is seen in radar
  images.
• This image is of the volcano, Aine Corona.
• Lava flows and domes are easily recognizable.

Figure 22.8
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HUBBLE SPACE TELESCOPE IMAGE MARS OPPOSITION OF
2001
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THE 2003 APPARITION OF MARS
A COMPARISON OF THE RELATIVE SIZE OF MARS AS SEEN
THROUGH THE SAME TELESCOPE WITH THE SAME
MAGNIFICATION. AS MARS COME TO OPPOSITION ON
AUGUST 27, THE DISTANCE SEPATATING EARTH AND MARS
REACHES ITS MINIMUM.
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Photograph Of Mars Taken with A 5 Inch
Refracting Telescope June 2003, 2
Months Before Opposition
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THE MOON AND MARS DURING A GRAZING
OCCULTATION JULY 17, 2003 COMPOSITE PHOTOGRAPH
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SUMMER
SPRING
SOUTHERN HEMISPHERE (AUSTRAL) SRPING ON MARS NOTE
HOW THE SOUTHERN ICE CAP OR FROST
COVER DIMINISHES INTO THE SUMMER
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PERCIVAL LOWELL AT THE 24 INCH REFRACTOR,
FLAGSTAFF, ARIZONA OBSERVING MARS DURING
FAVORABLE OPPOSTION (PERIHELIC OPPOSTION) OF
1894 BELOW IS A GLOBE CONSTRUCTED FROM
HIS DRAWINGS
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Tales of Canals and Life on Mars
Early observers (Schiaparelli, Lowell) believed
they saw canals on Mars
This, together with growth/shrinking of polar
caps, sparked imaginative sci-fi tales of life on
Mars.
We know today canals were simply optical
illusions
No direct evidence of life on Mars.
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Planet Mars

• Mars has the same length day as does the Earth.
• Mars is about half the size of the Earth.
• The atmosphere is about 1 as dense as Earth's.
• Carbon dioxide is the major gas in the atmosphere.

Figure 22.13
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The Atmosphere of Mars
Very thin Only 1 of pressure on Earths surface
95 CO2
Even the thin Martian atmosphere is evident
through haze and clouds and ice caps
Occasionally Strong dust storms can enshroud the
entire planet.
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Ice in the Polar Cap
South Polar cap contains mostly CO2 ice, but also
water.
Multiple ice regions separated by valleys free of
ice.
Boundaries of polar caps reveal multiple layers
of dust, left behind by repeated growth and
melting of polar-cap regions.
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Mars Panorama
Figure 22.14

• Mars really is a 'red planet' due to iron oxide
  in its soil.
• This wonderful panorama from the surface was
  taken by the Pathfinder on July 4, 1997.
• The haze and clouds in its thin atmosphere are
  easily seen.

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Opportunity Lander Site 2004
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Mars

• Diameter 1/2 Earths diameter

• Very thin atmosphere, mostly CO2

• Rotation period 24 h, 40 min.

• Axis tilted against orbital plane by 25o,
  similar to Earths inclination (23.5o)

• Seasons similar to Earth ? Growth and shrinking
  of polar ice caps

• Crust not broken into tectonic plates

• Former Volcanic activity (including highest
  extinct volcano in the solar system)

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The Atmosphere of Mars (2)
Most of the Oxygen bound in oxides in rocks
? Reddish color of the surface
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Planetary Gases
Over the 4.5 billion years since Mars was
formed, it has lost most of its low mass gases.
Figure 22.15
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Hidden Water on Mars
Liquid water can not exist on the surface at
present. It would evaporate due to low
atmospheric pressure.
But there is strong evidence for liquid water in
the past
Outflow channels from sudden, massive floods
Collapsed structures after withdrawal of
sub-surface water
Valleys resembling meandering river beds
Gullies, possibly from debris flows
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The Geology of Mars (2)
Northern Lowlands Free of craters probably
re-surfaced a few billion years ago.
Possibly once filled with water.
Southern Highlands Heavily cratered probably 2
3 billion years old.
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Volcanism on Mars (2)
Tharsis rise (volcanic bulge)
Nearly as large as the U.S.
Rises 10 km above mean radius of Mars.
Rising magma has repeatedly broken through crust
to form volcanoes.
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Olympus Mons

• Olympus Mons is the largest shield volcano in the
  solar system.
• It is much larger than Mauna Loa, the largest
  shield volcano on Earth.

Figure 22.18
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The Geology of Mars (2)
Northern Lowlands Free of craters probably
re-surfaced a few billion years ago.
Possibly once filled with water.
Southern Highlands Heavily cratered probably 2
3 billion years old.
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Color mosaic of Viking Orbiter 1 and 2 images
showing Candor Chasma, part of the Valles
Marineris system on Mars. This oblique view is
looking from the west over the 800 km wide chasm.
Tectonic rifting formed this great canyon system
but the walls and floor show evidence of erosion,
mass wasting and complex geomorphology possibly
modified by flowing water
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COMPOSITE IMAGE OF MARS TAKEN FROM SMALL
TELESCOPES ONBOARD THE 2 VIKING
ORBITERS EARLY 1970S
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Hidden Water on Mars (2)
Gusev Crater and Maadim Vallis
Giant lakes might have drained repeatedly through
the Maadim Vallis into the crater.
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Water on Mars

• Ancient Mars had flowing water on its surface.
• These images clearly show the results of what
  appears to have been flowing water.
• The Viking landers actually recorded frost
  forming, then evaporating.
• There does not seem to be any liquid water on
  Mars today.
• It is possible that there may be surface water in
  shallow lakes under ice.

Figure 22.20A
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Martian Terrain

• This Viking spacecraft image shows that Mars has
  earthlike terrain.
• Volcanoes, canyons, and plains are easily seen.

Figure 22.16
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Research Questions

• Current research is trying to answer the
  following questions.
• Was Mars warm and wet?
• Was Mars cold and dry?
• Was it a combination of these two questions?
• This image shows water related features on Mars.
• Where is the water now?

Figure 22.21A
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The Geology of Mars (2)
Northern Lowlands Free of craters probably
re-surfaced a few billion years ago.
Possibly once filled with water.
Southern Highlands Heavily cratered probably 2
3 billion years old.
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Volcanism on Mars
Volcanoes on Mars are shield volcanoes.
Olympus Mons
Highest and largest shield volcano in the solar
system.
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Martian Canals

• Percival Lowell mapped canals over the face of
  Mars.
• Schiaparelli recorded his observations of Mars
  and named the linear features he saw, 'canali'.
• Canali was translated as canals. To build canals
  requires intelligent beings.
• There are no canals on Mars.

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The Geology of Mars (2)
Northern Lowlands Free of craters probably
re-surfaced a few billion years ago.
Possibly once filled with water.
Southern Highlands Heavily cratered probably 2
3 billion years old.
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Mars Globes
Figure 22.17

• A full global view of Mars.
• The Viking and Pathfinder landing sites are
  marked.

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Martian Climate

• The north polar cap has regions of water ice as
  well as dry ice (frozen carbon dioxide).
• Mars' climate seems to have undergone periodic
  changes.
• This conclusion is based on the layering seen in
  various regions on the surface.

Figure 22.22A
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Color mosaic of Viking Orbiter 1 and 2 images
showing Candor Chasma, part of the Valles
Marineris system on Mars. This oblique view is
looking from the west over the 800 km wide chasm.
Tectonic rifting formed this great canyon system
but the walls and floor show evidence of erosion,
mass wasting and complex geomorphology possibly
modified by flowing water
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Hidden Water on Mars
Liquid water can not exist on the surface at
present. It would evaporate due to low
atmospheric pressure.
But there is strong evidence for liquid water in
the past
Outflow channels from sudden, massive floods
Collapsed structures after withdrawal of
sub-surface water
Splash craters and valleys resembling meandering
river beds
Gullies, possibly from debris flows
Central channel in a valley suggests long-term
flowing water
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Deimos Phobos

• Mars has two small moons called Deimos and
  Phobos.
• Cratering is evident even on these small moons.
• Phobos, the larger moon, is so close to Mars that
  it will be ripped apart by tidal forces or crash
  into Mars within about 100 million years.

Figure 22.25A
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Drainage Channels
Drainage channels and various erosion features
are seen in this image.
Figure 22.21A
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Opportunity Lander Site 2004
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Venus' Atmosphere

• Venus has an atmosphere of 96 carbon dioxide.
• The greenhouse effect on Venus is extreme.

Figure 22.1A
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Venus and Mars
Figure 22.1A
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Evidence for Water on Mars
Galle, the happy face crater
Meteorite ALH84001
Identified as ancient rock from Mars.
Some minerals in this meteorite were deposited in
water ? Martian crust must have been richer in
water than it is today.
Large impacts may have ejected rocks into space.