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Venus Introduction
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Venus Introduction
Advance in science comes by laying brick upon brick, not by sudden
erection of fairy palaces. - J. S. Huxley
Venus Introduction
Venus Introduction
Venus Statistics
Animations of Venus
Views of Venus
References
Venusian Impact Craters
Venusian Volcanic Features
Magellan Mission to Venus
Venus Exploration Chronology
Venus Photo/Animation Gallery
Planetary Icosahedrons
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Venus,
the jewel of the sky, was once know by ancient astronomers as
the morning star and evening star. Early astronomers
once thought Venus to be two separate bodies. Venus, which is named
after the Roman goddess of love
and beauty, is veiled by thick swirling cloud cover.
Astronomers refer to Venus as Earth's sister planet. Both are similar
in size, mass, density and volume. Both formed about the same time
and condensed out of the same nebula.
However, during the last few years scientists have found that the
kinship ends here. Venus is very different from the Earth. It has
no oceans and is surrounded by a heavy atmosphere
composed mainly of carbon dioxide with virtually no water vapor.
Its clouds are composed of
sulfuric acid droplets.
At the surface, the atmospheric pressure is 92 times that of the
Earth's at sea-level.
Venus is scorched with a surface temperature of about 482° C
(900° F).
This high temperature is primarily due to a runaway
greenhouse effect caused
by the heavy atmosphere of carbon dioxide. Sunlight passes through
the atmosphere to heat the surface of the planet. Heat is radiated out,
but is trapped by the dense atmosphere and not allowed
to escape into space. This makes Venus hotter than
Mercury.
A Venusian day is 243 Earth days and is longer than its year of
225 days. Oddly, Venus rotates from east to west. To
an observer on Venus, the Sun would rise in the west and set in the
east.
Until just recently, Venus' dense cloud cover has prevented scientists
from uncovering the geological nature of the surface. Developments
in radar telescopes and radar imaging systems orbiting
the planet have made it possible to see through the cloud deck to
the surface below. Four of the most successful missions in revealing the
Venusian surface are
NASA's Pioneer Venus mission (1978), the Soviet Union's Venera 15 and
16 missions (1983-1984), and NASA's Magellan radar mapping mission
(1990-1994). As these spacecraft began mapping the planet a new picture
of Venus emerged.
Venus' surface is relatively young geologically speaking. It appears to
have been completely resurfaced 300 to 500 million years ago. Scientists
debate how and why this occurred. The Venusian topography consists of
vast plains covered by lava flows and mountain or highland regions
deformed by geological activity. Maxwell Montes in Ishtar Terra is the
highest peak on Venus. The Aphrodite Terra highlands extend almost
half way around the equator. Magellan images of highland regions
above 2.5 kilometers (1.5 miles) are unusually bright, characteristic of moist soil.
However, liquid water does not exist on the surface and cannot account
for the bright highlands. One theory suggests that the bright material
might be composed of metallic compounds. Studies have shown the material
might be iron pyrite (also know as "fools gold").
It is unstable on the plains but would be stable in the highlands.
The material could also be some type of exotic material which would
give the same results but at lower concentrations.
Venus is scarred by numerous impact craters
distrubuted randomly over its surface. Small craters less that 2 kilometers
(1.2 miles) are almost non-existent due to the heavy Venusian atmosphere.
The exception occurs when large meteorites shatter just before impact, creating
crater clusters.
Volcanoes and volcanic features are even more numerous. At least 85% of
the Venusian surface is covered with volcanic rock. Hugh lava flows,
extending for hundreds of kilometers, have flooded the lowlands creating
vast plains. More than 100,000 small shield volcanoes dot the surface along
with hundreds of large volcanos. Flows from volcanos have produced long
sinuous channels extending for hundreds of kilometers, with one extending
nearly 7,000 kilometers (4,300 miles).
Giant calderas more than
100 kilometers (62 miles) in diameter are found on Venus. Terrestrial
calderas are usually only several kilometers in diameter. Several
features unique to Venus include coronae and arachnoids. Coronae are
large circular to oval features, encircled with cliffs and are hundreds
of kilometers across. They are thought to be the surface expression of
mantle upwelling. Archnoids are circular to elongated features similar
to coronae. They may have been caused by molten rock seeping into surface
fractures and producing systems of radiating dikes and fractures.
Venus Statistics
Mass (kg)4.869e+24
Mass (Earth = 1).81476
Equatorial radius (km)6,051.8
Equatorial radius (Earth = 1).94886
Mean density (gm/cm^3)5.25
Mean distance from the Sun (km)108,200,000
Mean distance from the Sun (Earth = 1)0.7233
Rotational period (days)-243.0187
Orbital period (days)224.701
Mean orbital velocity (km/sec)35.02
Orbital eccentricity0.0068
Tilt of axis (degrees)177.36
Orbital inclination (degrees)3.394
Equatorial surface gravity (m/sec^2)8.87
Equatorial escape velocity (km/sec)10.36
Visual geometric albedo0.65
Magnitude (Vo)-4.4
Mean surface temperature482°C
Atmospheric pressure (bars)92
Atmospheric composition
Carbon dioxideNitrogen
Trace amounts of: Sulfur dioxide, water vapor,carbon
monoxide, argon, helium, neon,hydrogen chloride, and
hydrogen fluoride.
96% 3+%
Animations of Venus
Rotating Venus Movie.
Venus Topography Animation.
Artist's view of Venus.
Earth/Venus Rotation Movie.
Magellan - Mapping the planet Venus.
Flight over Western Atla Regio.
Flight over Artemis.
Flight over Alpha Regio.
Flight over Western Eistla Regio.
A dramatic view the the moon with Venus in the distance.
Views of Venus
Venus with Visible and Radar Illumination
This picture shows two different perspectives of Venus.
On the left is a mosaic of images acquired by
the Mariner 10 spacecraft on February 5, 1974. The image
shows the thick cloud coverage that prevents optical
observation of the planet's surface. The surface of Venus
remained hidden until 1978 when the Pioneer Venus 1
spacecraft arrived and went into orbit about the planet
on December 4th. The spacecraft used radar to map
planet's surface, revealing a new Venus. Later in
August of 1990 the Magellan spacecraft arrived at
Venus and began its extensive planetary mapping mission.
This mission produced radar images up to 300 meters per pixel
in resolution.
The right image show a rendering of Venus from the
Pioneer Venus and Magellan radar images.
(Copyright Calvin J. Hamilton)
The Interior of Venus
This picture shows a cutaway view of the possible internal
structure of Venus. The image was created from Mariner 10
images used for the outer atmospheric layer. The surface
was taken from Magellan radar images. The interior
characteristics of Venus are inferred from gravity field
and magnetic field measurements by Magellan and prior
spacecraft. The crust is shown as adark red, the mantle as
a lighter orange-red, and the core yellow.
More ...
(Copyright Calvin J. Hamilton)
Mariner 10 Image of Venus
This beautiful image of Venus is a mosaic of three images acquired by
the Mariner 10 spacecraft on February 5, 1974.
It shows the thick cloud coverage that
prevents optical observation of the surface of Venus. Only through
radar mapping is the surface revealed.
(Copyright Calvin J. Hamilton)
Galileo Image of Venus
On February 10, 1990 the Galileo spacecraft acquired this image of
Venus. Only thick cloud cover can be seen.
(Copyright Calvin J. Hamilton)
Hubble Image of Venus
This is a Hubble Space Telescope ultraviolet-light image of the
planet Venus, taken on January 24, 1995, when Venus was at a distance of
113.6 million kilometers from Earth.
At ultraviolet wavelengths cloud patterns become distinctive. In
particular, a horizontal "Y" shaped cloud feature is visible near
the equator.
The polar regions are bright, possibly showing a haze of small
particles overlying the main clouds. The dark regions show the
location of enhanced sulfur dioxide near the cloud tops. From previous
missions, astronomers know that such features travel east to west along
with the Venus' prevailing winds, to make a complete circuit around the
planet in four days.
(Credit: L. Esposito, University of Colorado, Boulder, and NASA)
Hemispheric View of Venus
This hemispheric view of Venus, as revealed by more than a decade
of radar investigations culminating in the 1990-1994 Magellan
mission, is centered at 0 degrees east longitude.
The effective resolution of this image is about
3 kilometers. It was processed to improve
contrast and to emphasize small features, and was color-coded to
represent elevation.
(Courtesy NASA/USGS)
Additional Hemispheric Views of Venus
View centered at 90°E longitude.
View centered at 180°E longitude.
View centered at 90°W longitude.
View centered at the north pole.
View centered at the south pole.
Venusian Map
This image is a Mercator projection of Venusian topography. Many of
the different regions have been labeled. The map extends from -66.5 to
66.5 degrees in latitude and starts at 240 degrees longitude.
(Copyright Calvin J. Hamilton)
Venusian Topography Map
This is another Mercator projection of Venusian topography. The map
extends from -66.5 to 66.5 degrees in latitude and starts at 240
degrees longitude. A Black &
White version of this image is also available.
(Courtesy A.Tayfun Oner)
Gula Mons and Crater Cunitz
A portion of Western Eistla Regio is displayed in this three
dimensional perspective view of the surface of Venus. The
viewpoint is located 1,310 kilometers (812 miles) southwest of
Gula Mons at an elevation of 0.78 kilometers (0.48 mile). The
view is to the northeast with Gula Mons appearing on the horizon.
Gula Mons, a 3 kilometer (1.86 mile) high volcano, is located at
approximately 22 degrees north latitude, 359 degrees east
longitude. The impact crater Cunitz, named for the astronomer
and mathematician Maria Cunitz, is visible in the center of the
image. The crater is 48.5 kilometers (30 miles) in diameter and
is 215 kilometers (133 miles) from the viewer's position.
(Courtesy NASA/JPL)
Eistla Regio - Rift Valley
A portion of Western Eistla Regio is displayed in this three
dimensional perspective view of the surface of Venus. The
viewpoint is located 725 kilometers (450 miles) southeast of Gula
Mons. A rift
valley, shown in the foreground, extends to the base of Gula
Mons, a 3 kilometer (1.86 miles) high volcano. This view is facing
the northwest with Gula Mons appearing at the right on the
horizon. Sif Mons, a volcano with a diameter of 300
kilometers (180 miles) and a height of 2 kilometers (1.2 miles),
appears to the left of Gula Mons in the background.
(Courtesy NASA/JPL)
Eistla Regio
A portion of Western Eistla Regio is displayed in this three
dimensional perspective view of the surface of Venus. The
viewpoint is located 1,100 kilometers (682 miles) northeast of
Gula Mons at an elevation of 7.5 kilometers (4.6 miles). Lava
flows extend for hundreds of kilometers across the fractured
plains shown in the foreground, to the base of Gula Mons. This view
faces the southwest with Gula Mons appearing at the left
just below the horizon. Sif Mons
appears to the right of Gula Mons. The
distance between Sif Mons and Gula Mons is approximately 730
kilometers (453 miles).
(Courtesy NASA/JPL)
Lakshmi Planum
The southern scarp and basin province of western Ishtar Terra are
portrayed in this three dimensional perspective view. Western Ishtar Terra
is about the size of Australia and is a major focus of
Magellan
investigations. The highland terrain is centered on a 2.5 km to
4 km high (1.5 mi to 2.5 mi high) plateau called Lakshmi
Planum which
can be seen in the distance at the right. Here the surface of the
plateau drops precipitously into the bounding lowlands, with steep
slopes that exceed 5% over 50 km (30 mi).
(Courtesy NASA/JPL)
Three-Dimensional Perspective View of Alpha Regio
A portion of Alpha Regio is displayed in this three-dimensional
perspective view of the surface of Venus. Alpha Regio, a
topographic upland approximately 1300 kilometers across, is centered on
25 degrees south latitude, 4 degrees east longitude. In 1963, Alpha Regio
was the first feature on Venus to be identified from earth-based radar.
The radar-bright area of Alpha Regio is characterized by multiple sets of
intersecting trends of structural features such as ridges, troughs, and
flat-floored fault valleys that, together, form a polygonal outline.
Directly south of the complex ridged terrain is a large ovoid-shaped
feature named Eve. The radar-bright spot located centrally within Eve
marks the location of the prime meridian of Venus.
(Courtesy NASA/JPL)
Arachnoids
Arachnoids are one of the more remarkable features found on
Venus. They are seen on radar-dark plains in this Magellan image mosaic
of the Fortuna region. As the name suggests,
arachnoids are circular to ovoid features with concentric rings and
a complex network of fractures extending outward.
The arachnoids range in size from approximately 50 kilometers (29.9
miles) to 230 kilometers (137.7 miles) in diameter. Arachnoids are
similar in form but generally smaller than coronae
(circular volcanic structures surrounded by a set of ridges and
grooves as well as radial lines). One theory concerning their
origin is that they are a precursor to coronae formation. The
radar-bright lines extending for many kilometers might have resulted
from an upwelling of magma from the interior of the planet
which pushed up the surface to form "cracks." Radar-bright lava
flows are present in the 1st and 3rd image, also
indicative of volcanic activity in this area. Some of the
fractures cut across these flows, indicating that the flows
occurred before the fractures appeared. Such relations between
different structures provide good evidence for relative
age dating of events.
(Courtesy NASA/JPL)
Parallel Lines
Two groups of parallel features that intersect almost at right angles
are visible. The regularity of this terrain caused scientists to nickname
it graph paper terrain. The fainter lineations are spaced at intervals
of about 1 kilometer (.6 miles) and extend beyond the boundaries of the image. The
brighter, more dominant lineations are less regular and often appear to
begin and end where they intersect the fainter lineations. It is not yet
clear whether the two sets of lineations represent faults or fractures,
but in areas outside the image, the bright lineations are associated with
pit craters and other volcanic features.
(Courtesy Calvin J. Hamilton)
Surface Photographs from Venera 9 and 10
The Soviet Venera 9 and 10 spacecraft were launched on 8 and 14 June 1975,
respectively, to do the unprecedented: place landers on the surface of
Venus and return images. The Venera 9 Lander (top) touched down on the surface
of Venus on October 22, 1975 at 5:13 UT, about 32° S, 291° E with the sun
near zenith. It operated for 53 minutes, allowing return of a single
image. Venera 9 landed on a slope inclined by about 30 degrees to the
horizontal. The white object at the bottom of the image is part of
the lander. The distortion is caused by the Venera imaging system.
Angular and partly weathered rocks, about 30 to 40 cm across, dominate
the landscape, many partly buried in soil. The horizon is visible in the
upper left and right corners.
The Venera 10 Lander (bottom) touched down on the surface of Venus on
October 25, 1975 at 5:17 UT, about 16° N, 291° E. The Lander
was inclined about 8 degrees. It returned this image during the 65
minutes of operation on the surface. The sun was near zenith during this
time, and the lighting was similar to that on Earth on an overcast summer
day. The objects at the bottom of the image are parts of the spacecraft.
The image shows flat slabs of rock, partly covered by fine-grained material,
not unlike a volcanic area on Earth. The large slab in the foreground
extends over 2 meters across.
Color Surface Photographs from Venera 13
On March 1, 1982 the Venera 13 lander touched down on the Venusian
surface at 7.5° S, 303° E, east of Phoebe Regio. It was the first
Venera mission to include a color TV camera. Venera 13 survived on the
surface for 2 hours, 7 minutes, long enough to obtain 14 images.
This color panorama was produced using dark blue, green and red
filters and has a resolution of 4 to 5 min. Part of the
spacecraft is seen at the bottom of the image. Flat rock slabs and
soil are visible. The true color is difficult to judge because the
Venerian atmosphere filters out blue light. The surface composition
is similar to terrestrial basalt. On the ground in the foreground is a
camera lens cover. This image is the left half of the Venera 13 photo.
Surface Photographs from Venera 13.
Surface Photographs from Venera 14.
References
Ford, John P. et al. Guide to Magellan Image Interpretation.
JPL Publication 93-24, 1993.
Robinson, Cordula. "Magellan Reveals Venus." Astronomy,
32-41, February 1995.
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Views of the Solar System Copyright © 1997-2001 by
Calvin J. Hamilton. All rights reserved.
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