Transcript Venus Surface

Venus
Venus Facts
Venus Diameter:
12,104 km, 0.95 Earth Diameters
Planetary Mass:
4.86x1024 kg, 0.82 Earth masses
Density:
5.24 g/cm3
Avg. Dist. from Sun:
108 million km, 0.7233 AU
Closest dist. to Earth:
38 million km
Number of moons:
0
Magnetic field:
None
Average temperature:
460oC on both the day and night
sides
Atmospheric composition: 96.5% Carbon Dioxide (CO2),
3.5% Nitrogen (N2)
Venus Facts – cont.
Axial tilt:
177.3o, which means that it is
rotating in space upside down! It’s
axis is only 2.7o tilted from ecliptic,
which isn’t enough to cause seasons.
Length of Day:
(clockwise)
243 Earth days backwards
Length of Year:
225 Earth days
Name Origin
• Named after the Roman goddess
of love and beauty.
• The planet was named Venus
because it was the brightest of the
planets known to the ancients.
• Commonly called the “evening
star” or the “morning star”
• Much brighter than any star.
• Originally the Greeks thought
Venus was two different planets.
Peculiar Rotation
• Rotation is retrograde: rotation is opposite of the direction
of orbital motion
– Orbit motion around the Sun: counterclockwise
– Venus’s rotation on its axis: clockwise
– Planets and satellites have prograde rotation except
Venus, Uranus and Pluto
Appearance of Venus
• Simple telescopes can detect
that Venus goes through
phases like the Moon
• It can often seen in the
eastern sky at dawn or in the
western sky after sunset
• Surface is always obscured
by a very dense cloud cover
• Clouds reflect 70% of the
sunlight, causing its
brightness
Enhanced picture of Venus shot through
a violet filter by the Galileo spacecraft
Phases of Venus
• Venus appears to go through phases like the moon
• Different from the moon because its distance from us
changes drastically
Venus Interior
• Internal composition is
probably similar to Earth.
• It is possible that the core is
liquid iron.
• Core has less mass than
Earth’s (only 23% of total
planet).
• Based on size, Venus should
be heavier
• We do not know if the core
contains less iron or if it is
smaller than Earth’s.
Interior
• The presence of volcanoes suggests a molten interior
• Venus has no planet-wide magnetic field, possibly due to
the fact that Venus rotates too slowly.
• Venus has no plate
tectonics, possibly
due to that the crust is
too hot and soft to
move in rigid plates
Venus Atmosphere
•
•
•
•
Atmosphere of mainly CO2
Clouds of sulfuric acid
No water
Crushing atmospheric
pressure of about 90 atm
• High-velocity winds in upper
atmosphere but low-velocity
surface winds (we don’t
know why)
• High surface temperatures
from “Greenhouse Effect”
• Slow surface erosion rate
• High clouds with a clear CO2 atmosphere below.
• Much warmer atmosphere near the planet’s surface
than Earth’s, but colder at high altitudes.
Greenhouse Effect
The sunlight that is able to pass through the clouds
warms the surface. The surface then re-radiates heat
upwards. The heat becomes trapped below the clouds.
The result is a much higher surface temperature than
would be present without the blanketing effect of the
atmosphere.
Carbon dioxide cycle on Earth keeps us from
being like Venus
But this cycle would not work if there’s no liquid water!
Venus Atmospheric Missions
• Mariner 10 – Fly-by in 1973 on
its way to Mercury
• Pioneer Venus – Five probes in
1978
• Vega 1 and 2 – Two probes in
1985
• Galileo – Fly-by in 1990
• Europe’s Venus Express - 2006
• Messenger – Made fly-bys in
2006 and 2007 on its way to
Mercury
Pioneer Venus
1978
Orbiter
Venus Atmosphere
Venus Topography
Visible versus Radar
• Orange colors in
radar images are
not “real”.
• Colors have
been enhanced
to show surface
features more
clearly
Venus Surface
• Surface rocks are basaltic (similar to our
ocean floor).
• Dense atmosphere prevents studying the
surface from orbit.
• Craters and “pristine” appearance
suggest young surface.
• No plate tectonics
• No true continents or ocean basins
• We do not know the range of ages of the
rocks on the surface
• We do not know how the surface
changed with time
Surface
• The surface of Venus is surprisingly flat, with only a few
major highlands and several large volcanoes
• The surface of Venus shows no evidence of plate tectonics (or
the motion of large crustal plates)
– No long chain of volcanic mountains
Venus Surface Features
Planitia: Low plains
Terra: Extensive land masses
Planum: Plateaus
Corona: Ovoid-shaped volcanic features
Volcanic craters: numerous
Impact Craters: about 1000, randomly distributed
Volcanic Structures
Shield Volcanoes
• Low-sloping volcanoes
formed from repeated
eruptions of low-viscosity
lava
Sif Mons Shield Volcano
Impact Craters
Yablochkina impact crater
• Radar images from Magellan
• Bright regions: high radar reflectivity – “rough”
• Dark regions: low reflectivity – “smooth”
Addams Impact Crater
The radar bright outflow associated with the 90 km crater
stretches over 600 km to the east.
Lava Channel
The channel is about
2 km wide and shows
branches and islands
along its length.
The image shown
here is about 50 km
wide.
Probably low
viscosity, high
temperature lava.
Volcanic “Pancake" Domes
• Flattened tops and
steep edges.
• Probably formed by
the eruption of thick
lava.
• High atmospheric
pressure likely caused
the flattened tops
• The largest dome is 62
km in diameter.
“Tick”
• Volcanic feature
• Dome with a large
volcanic vent
(caldera)
• Surrounded by
radial spurs that
look like legs.
Nova
Magellan image of a nova.
•A pattern of hills and valleys
that radiate outward from a
single point.
•This nova is about 250 km in
diameter
Maxwell Montes
• The Maxwell Montes are the highest mountains on
Venus
• rising up to 11 km above the surface.
Venus Surface Studies
• Mariner 2: First planetary mission in 1972
• Pioneer Venus: Topography and atmospheric
probes in 1978
• Veneras 8 – 14: Surface landers from 1975-1982
• Veneras 15 & 16: Orbital radars, 1984
• Magellan: Orbital radar images, topography
and gravity data, 1990-1994
• Europe’s Venus Express: 2006
Venus Surface Studies
Orbital Missions: Pioneer Venus, Magellan.
Surface Missions: Vega and Venera
Future studies:
• NASA and the ESA are looking
into the possibility of sending a
lander to Venus to collect rock
samples and return them to Earth
for analysis
• New generation of surface
measurements by landed
spacecraft.
• Still in the proposal stage
Proposed Venus Sample Return mission
6 years round trip
Venera Lander Images of Venus
Venera 9
1975
53 min. surface operation
Venera 13
1982
2 hrs 7 min. surface operation
Venera 10
1975
65 min. surface operation
Venera 14
1982
60 min. surface operation
Magellan
1989-1994
The primary objective of the mission was to map the
surface the surface features of Venus
98% of the surface was imaged at high resolutions
Magellan
Volcanic "pancake" domes in
Tinatin Planitia, Venus
Computer generated 3-dimensional
perspective view of the "crater farm"
At 280 km diameter, Mead
Crater is the largest impact
crater on Venus.
3-dimensional image of Sapas Mons
a 1.5 km high volcano
Top Ten Questions about Venus
1.
Was Venus ever a habitable planet?
2.
Did Venus possess abundant surface water in its early history?
3.
What is the nature of weathering on the Venusian surface?
4.
What has been the composition and evolutionary history of the Venusian
atmosphere?
5.
What has been the volcanic history of Venus over time?
6.
Did Venus ever have plate tectonics?
7.
What has been the cratering rate on Venus over time?
8.
What are the ages of different rocks and features on Venus’ surface?
9.
What is the overall chemical composition of Venus and how does it
compare to other planetary bodies in the solar system?
10. What are the geophysical properties (heat flow, seismic activity, etc.) of
the interior and what do they reveal about the internal structure of Venus?