Venus and the Magellan
mapping project:
1. What direction does
Venus rotate? Describe theories for why this might be.
If you
look at the planets rotating on their planes from a Birdseye view, you’ll
notice something unique about Venus. Almost all planets rotate in a counter
clockwise manner around the plane. One of the two planets that rotates
clockwise is Venus. This direction is east to west and is called a retrograde
rotation. This phenomenon is not very well understood but scientists
do have some theories.
1. Some astronomers have a
theory that billions of years ago, an extremely large object hit Venus. This
collision would have been enough to reverse the direction of rotation. In
addition some people believe that when the other object or planet hit, it’s
rotational direction and speed averaged out with that of Venus. Below are some
of the other theories, but this is the most common.
2. Another idea is that the
axis could have flipped over, causing the retrograde rotation. This flip
may have been a result of the Sun’s pull on Venus’s very dense atmosphere. This
pull would have created very strong atmospheric tides. These strong tides and
friction between the planet’s inner core and mantle might have caused Venus’s
axis to flip 180 degrees. This means that the planet has in fact been spinning
the same way forever, it might just appear to be spinning in the opposite
direction because of the flip.
3. Also, instead of the
axis flipping, some scientists believe that a result of the Sun’s gravitational
force combined with the gravitational force of surrounding planets combined
with the tides once caused Venus’s rotation to come to a complete stop before
it continued to rotate the opposite direction.
4. A last idea is that
during the formation of the solar system, a planet will rotate one way or
another depending on which side had more impacts.
Oddly,
Venus takes about 7.5 Earth months to revolve around the sun and 8 months to
rotate on its axis. This is strange because it means that its “day” is longer
than its “year.” One theory is that the planet that hit Venus and made it spin
clockwise a million years ago, is also responsible for making Venus rotate
around its axis at a slower rate.To further explain, when the unknown planet
and Venus collided, it’s momentum combined with Venus’s. As a result the planet
slowed down the rotational velocity that Venus might have today, had the other
planet not hit. Another one of these theories is that the thick atmosphere that
surrounds the planet is affected strongly by the tides, and might possibly be
causing the planet to rotate around its axis at a very slow rate.
Because of the extreme temperatures and pressure on Venus, it is very tricky to send landers, but the Soviets have done it. The first lander on Venus only lasted for about 23 minutes but it was the first to send information back and it did take some pictures along with measurements of Venus’s temperature. This was the Venera 7. The Venera 8 sent us atmospheric data and lasted for 50 minutes. The Venera 9 orbited Venus and it successfully land on the surface. When it landed, it took pictures along with a 180-degree panorama! The pictures were photographed in UV light and allowed us to see that the illumination at the surface was equivalent to a cloudy day on Earth. The rocky surface of Venus also appeared in the pictures. From Gamma rays, scientists could tell that they had landed on basalt. The Venera 9 was a great success, sending back information for 53 minutes. Veneras 10, 11,12,13,14 and 15 found additional data such as information about the soil, atmosphere, and rocks. The longest mission was the taken by the Venera 12, which sent info for 110 minutes before the heat and pressure got to it.
The panorama taken by Venera 9.
The surface of Venus is actually pretty smooth in a
lot of places. It is a very dry place. A lot of features that are found on our
planet can be found on Venus. Some of these features are canyons, volcanoes,
lava flows, rift valleys, mountains, craters, and plains. The surface looks to
be in only one crustal plate unlike earth. Because most meteors burn up in
Venus’s atmosphere their aren’t many craters. The few craters that were created
are now covered by old lava flows.
Imagine living on Venus. Venus has a very thick
atmosphere, making everyday a cloudy day. There is never a time when Venus has
a nice, sunny day. When astronomers try to look at it from earth, all that is
visible is the smooth layer of cloud that is constantly surrounding the planet.
The pressure of Venus’s atmosphere compared to Earth’s is 90 times greater! In
addition you wouldn’t be able to breath if you went to Venus because the
atmosphere is primarily made up of Carbon Dioxide (95.5 percent) and partly
made up of sulfuric acid along with other trace gases. The last problem with
living on Venus is the temperature. We have learned how the greenhouse effect
takes a toll on Earth but lets think about Venus. On Venus, there is even more
energy from the sun than on Earth. Light from the sun heats up Venus’s surface.
When the surface heats up, it eventually begins to give off heat. Since Carbon
Dioxide is a greenhouse gas and there is so much of it in the atmosphere, it
absorbs the heat given off by the surface. This process called the greenhouse
effect causes Venus to reach temperatures of about 460 degrees Celsius. To
say the least, living on Venus wouldn’t be ideal because of the constant
clouds, crushing atmosphere, lack of air, and greenhouse effect.
Scientists have collected evidence mostly through
the Magellan Probe. In 1990, the probe reached Venus. Magellan carried radar
instruments, and since they are able to work through the clouds, Magellan
mapped out the entire surface of Venus! The views from Magellan were amazingly
detailed; allowing computers to show us what Venus would look like from just
feet above the surface. These radar images showed that Venus is covered with
rock, lava flows, craters, and unique domes that cannot be found on any other
planet.
Some scientists believe that there
are still active volcanoes on Venus but they are not entirely sure. Almost the
whole surface is made up of volcanoes so it would be unlikely that there are no
active ones. We know for certain that
the volcanoes on Venus have once been active though because of the channels
that scientists have seen on the surface. These channels would have to be made
from lava, not water because we know that the water would’ve just boiled off.
Also, there are other volcanic features that resemble pancakes, and volcanoes
that are called tick volcanoes. Because
there are not many craters on Venus, it shows us that all craters recent, and
old might have just been covered by recent lava. A huge piece of evidence is that the European
Space Agency found 3 volcanoes that were active between 200 and 2.5 million
years ago. Around this area, scientists found lava flows that were fairly
young. They know these lava flows are young because they are capable of
emitting infrared heat.
A
common question people ask is: Are there plate tectonics on Venus? Well the
answer is no. On Earth, we can clearly map out our volcanoes and see that they
make up the right of fire, a string of volcanoes and earthquakes that border
the plate boundaries. On Venus, there are no strings of volcanoes, they are
randomly scattered. Lastly, there are no subduction zones, and although there
may be rifts, there are no mid-ocean ridges.
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