Archived Pages from 20th Century!!
Bringer of Peace
- Venus is the second planet from the Sun
and the sixth largest:
- distance from Sun: 108,200,000 km (0.72 AU)
- diameter: 12,103.6 km
- mass: 4.869e24 kg
Venus's orbit is the most nearly circular of that of any planet, with
an eccentricity of less than 1%.
- Venus (Greek: Aphrodite;
Babylonian: Ishtar) is the goddess of love and beauty. The planet is so
named probably because it is the brightest
of the planets known to the ancients. (With a few exceptions, the surface
features on Venus are named for female figures.)
- Venus has been known since prehistoric times. It is the brightest object
in the sky except for the Sun and the Moon. Like Mercury,
it was popularly thought to be two separate bodies: Eosphorus as the morning
star and Hesperus as the evening star, but the Greek astronomers
- Since Venus is an inferior
planet, it shows phases when viewed with a telescope from the perspective
of the Earth. Galileo's observation of this phenomenon was important evidence
in favor of Copernicus's
theory of the solar system.
- The first spacecraft to visit Venus was Mariner
2 in 1962. It was subsequently visited by many others (more than 20
in all so far), including Pioneer
Venus and the Soviet Venera
7 the first spacecraft to land on another planet, and Venera
9 which returned the first photographs of the surface. Most recently,
the orbiting US spacecraft Magellan
produced detailed maps of Venus's surface using radar.
- Venus's rotation is somewhat unusual in that it is both very slow (243
Earth days per Venus day, slightly longer than Venus's year) and retrograde.
In addition, the periods of Venus's rotation and of its orbit are synchronized
such that it always presents the same face toward Earth when the two planets
are at their closest approach.
- Venus is sometimes regarded as Earth's
sister planet. In some ways they are very similar:
- Venus is only slightly smaller than Earth (95% of Earth's diameter,
80% of Earth's mass).
- Both have few craters indicating relatively young
- Their densities and chemical compositions are similar.
Because of these similarities, it was thought that below its dense clouds
Venus might be very Earthlike and might even have life. But, unfortunately,
more detailed study of Venus reveals that in many important ways it is
radically different from Earth.
- The pressure of Venus's atmosphere at the surface is 90 atmospheres
(about the same as the pressure at a depth of 1 km in Earth's oceans).
It is composed mostly of carbon dioxide. There are several layers of clouds
many kilometers thick composed of sulfuric acid. These clouds completely
obscure our view surface (picture 2). This dense atmosphere
produces a run-away greenhouse
effect that raises Venus's surface temperature by about 400 degrees
to over 740 K (hot enough to melt lead). Venus's surface is actually hotter
despite being nearly twice as far from the Sun.
- There are strong (350 kph) winds at the cloud tops (picture
6) but winds at the surface are very slow, no more than a few kilometers
- Venus probably once had large amounts of water like Earth but it all
boiled away. Venus is now quite dry. Earth would have suffered the same
fate had it been just a little closer to the Sun. We may learn a lot about
Earth by learning why the basically similar Venus turned out so differently.
- Most of Venus's surface consists of gently rolling plains with little
relief. There are also several broad depressions: Atalanta Planitia,
Guinevere Planitia, Lavinia Planitia. There two large highland
areas: Ishtar Terra in the northern hemisphere (about the size of
Australia) and Aphrodite Terra along the equator (about the size
of South America). The interior of Ishtar consists mainly of a high plateau,
Lakshmi Planum, which is surrounded by the highest mountains on
Venus including the enormous Maxwell Montes.
- Data from Magellan's
imaging radar shows that much of the surface of Venus is covered by lava
flows. There are several large shield volcanoes (similar to Hawaii or Olympus
Mons) such as Sif Mons (picture 3). Recently
announced findings indicate that Venus is still volcanically active, but
only in a few hot spots (picture 4); for the most part
it has been geologically rather quiet for the past few hundred million
- There are no small craters on Venus. It seems that small meteors burn
up in Venus's dense atmosphere before reaching the surface. Craters on
Venus seem to come in bunches (picture 11) indicating
that large meteors that do reach the surface usually break up in the atmosphere.
- The oldest terrains on Venus seem to be about 800 million years old.
Extensive volcanism at that time wiped out the earlier surface including
any large craters from early in Venus's history.
- Magellan's images show a wide variety of interesting and unique features
including pancake volcanoes which seem to be eruptions of very thick
lava (picture 8) and coronae which seem to be
collapsed domes over large magma chambers (picture 9).
- The interior of Venus is probably very similar to that of Earth: an
iron core about 3000 km in radius, a molten rocky mantle comprising the
majority of the planet. Recent results from the Magellan gravity data indicate
that Venus's crust is stronger and thicker than had previously been assumed.
Like Earth, convection
in the mantle produces stress on the surface which is relieved in many
relatively small regions instead of being concentrated at plate
boundaries as is the case on Earth.
- Venus has no magnetic field, perhaps because of its slow rotation.
- Venus has no satellites, and thereby hangs a tale.
- Venus is usually visible with the naked eye. Sometimes (inaccurately)
refered to as the "morning star" or the "evening star",
it is by far the brightest "star" in the sky. Mike Harvey's planet
finder charts show the current position of Venus (and the other planets)
in the sky.
- (above) False color high-res image a whole hemisphere 342k
light view from Galileo 73k
Mons 156k gif;
Impact Crater 131k
from Pioneer Venus 15k
- Gula Mons and Cunitz crater 250k
pancake volcanoes, alpha region 227k
Corona, Lada Terra 177k
- Vires-Akka Chasma, Denitsa Region 130k
- Crater Farm, Lavinia Region, small 107k
- Volcano, 3 mile diameter, paragon chasma, 9.4S by 247.5 long 282k
- Golubkina crater, 60.5 Deg N, 287.2 Long (computer generated Perspective)
- Alpha Regio, showing hills and craters 237k
image from HST (false color) 23k
- New Magellan global mosaics html
from Venera 9 and 10 108k
- NASA PDS Magellan Image Browser html
- ... more Venus
- Venus animation 1542K
- Venus Globe Animation 303k
- Earth/Venus Rotation Movie 1000k
- Magellan - Mapping the planet Venus 10000k
- Flight over Western Atla Regio 7000k
- Flight over Artemis 11000k
- Flight over Alpha Regio 8000k
- Flight over Western Eistla Regio - 3300k
- A dramatic view the the moon with Venus in the distance 82k
More about Venus
- There is some evidence of spreading and folding on Venus's surface
and of recent volcanic flows. But there is no evidence of plate
tectonics as seen on Earth. Is this a result of the higher surface
- The greenhouse effect is much stronger on Venus than Earth because
of Venus's dense carbon dioxide atmosphere. But why did Venus evolve so
differently from Earth?
... Venus ... Earth
Arnett; last updated: 1996 May 3